JP6573250B2 - Method for producing non-aqueous electrolyte secondary battery - Google Patents

Description

  The present invention relates to a method for manufacturing a nonaqueous electrolyte secondary battery.

  In recent years, the development of electric vehicles (EV), hybrid electric vehicles (HEV), and fuel cell vehicles (FCV) has been promoted against the background of the increasing environmental protection movement. As these motor driving power sources, motor driving electric devices such as secondary batteries that can be repeatedly charged and discharged are suitable. In particular, non-aqueous electrolyte secondary batteries that can be expected to have high capacity and high output, particularly lithium ion secondary batteries, are attracting attention, and are currently being developed rapidly.

The nonaqueous electrolyte secondary battery has a positive electrode active material layer containing a positive electrode active material (for example, LiCoO ₂ , LiMnO ₂ , LiNiO _2, etc.) formed on the current collector surface. In addition, the non-aqueous electrolyte secondary battery includes a negative electrode active material (for example, carbonaceous material such as metallic lithium, coke and natural / artificial graphite, Sn, A negative electrode active material layer including a metal such as Si or an oxide material thereof. Furthermore, the nonaqueous electrolyte secondary battery includes an electrolyte layer that is provided between the positive electrode active material layer and the negative electrode active material layer and includes an electrolyte that separates the positive electrode active material layer and the negative electrode active material layer. ing.

  Among these, the positive electrode having the positive electrode active material layer formed on the current collector surface is usually formed by applying a positive electrode slurry containing the positive electrode active material on the current collector surface. A negative electrode having a negative electrode active material layer formed on the current collector surface is usually formed by applying a negative electrode slurry containing a negative electrode active material to the current collector surface.

  Specifically, the positive electrode slurry is usually added with a solvent (N-methyl-2-pyrrolidone (NMP) or the like) in which a binder such as polyvinylidene fluoride (PVDF) is dissolved in a positive electrode active material or a conductive aid such as acetylene black. The mixture is further mixed, and the solvent is added and mixed to adjust the viscosity. Similarly, the negative electrode slurry is usually prepared by adding a solvent (NMP) in which a binder such as PVDF is added to a conductive auxiliary agent such as a negative electrode active material and acetylene black, and further mixing and adjusting the viscosity. Is done.

  The method for preparing the positive electrode raw material by the positive electrode slurry obtained above is as follows. First, a thin film (Al foil) of aluminum (thickness of about 20 μm) is purchased in a roll to form a positive electrode current collector foil, and the positive electrode slurry is formed on the surface of the positive electrode current collector foil. Is applied, dried, and roll-pressed to prepare a positive electrode raw material. Similarly, the negative electrode raw material by the negative electrode slurry obtained above is prepared by first purchasing a thin film (Cu foil) of copper (thickness of about 10 μm) as a negative electrode current collector foil, and the surface of the negative electrode current collector foil. A negative electrode slurry is applied to the substrate, dried, and roll-pressed to prepare a negative electrode raw material.

  The electrode (positive electrode and negative electrode) raw material and the separator raw material obtained above are cut into a rectangular shape of a desired size by a slitter, and dried to become a positive electrode, a negative electrode, and a separator. By laminating these positive electrodes, negative electrodes, and separators alternately in the order of positive electrode, separator, negative electrode, separator, positive electrode,..., A laminate having a desired number of layers (number of cells) is obtained. In addition, the separator original fabric purchased the microporous film (thickness of about 25 micrometers) made from polyethylene (PE) etc. with the roll, and was used as the separator original fabric.

  Next, after the positive electrode and the negative electrode current collector plate (positive electrode, negative electrode tab) are joined to the laminate (each current collector) with an ultrasonic welding machine, the battery outer body, for example, a rectangular laminate sealing body is formed. It is set as the sealing body before liquid injection by 3 side sealing (heat sealing) of 4 sides. An electrolyte solution is injected into the pre-injection sealed body with an injection device. As a result, an electrolyte layer in which the separator is impregnated with the electrolytic solution is formed. Thereafter, the remaining side of the laminate sealing body is sealed (heat sealed), whereby a battery can be manufactured.

  Here, the main component of the electrolytic solution is generally an electric vehicle (EV) (a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC)). In addition, an electrolyte (additive for SEI formation) for forming a protective film (hereinafter referred to as SEI; Solid Electrolyte Interface) generated at the time of initial charge on the active material surface on the negative electrode side is mixed with the electrolyte. Is used (see Patent Document 1).

  As described in Patent Document 1, as an effect of the additive, as the SEI generated on the negative electrode surface is initially charged, the increase in resistance is suppressed by generating a product derived from the additive, and on the electrode surface. It is known that there is an effect of suppressing the electrolytic solution decomposition and improving the battery life.

JP 2010-129192 A

  However, Patent Document 1 has not yet reached a point where the battery manufacturing process is devised to improve performance by generating uniform (high quality) SEI.

  That is, it is considered that SEI has a desirable composition and uniform film thickness. However, in the conventional battery manufacturing process such as Patent Document 1, the SEI formation additive is dissolved in the electrolytic solution, and injected into the inside of the sealing body before injection (stacked body thereof). The formation of SEI starts from the outside of the electrode with good electrolyte permeability. As SEI formation further proceeds, the additive present on the positive electrode side moves to the negative electrode and begins to form SEI. At that time, the SEI is formed from the outer side of the electrode having good permeability in the same manner as described above. As a result, a battery having different thickness and composition of SEI formed on the surface of the negative electrode active material near the current collector inside the electrode and the surface of the negative electrode active material near the outside of the electrode (active material layer) is obtained. The SEI becomes thicker). One of the purposes of the initial charging process is the formation of SEI. However, in order to follow the complicated process as described above, the time required to complete the formation of SEI by high-temperature aging after charging time and further by room temperature aging is completed. There was a problem that it was necessary for a long time and quality variation occurred.

  Accordingly, the present invention provides a method for producing a non-aqueous electrolyte secondary battery capable of improving battery performance by generating a high-quality SEI film (the film thickness is uniform in the thickness direction of the negative electrode active material layer). With the goal.

  The present invention is a method for producing a non-aqueous electrolyte secondary battery, wherein the negative electrode slurry used for negative electrode formation contains an additive for SEI formation.

  According to the negative electrode of the present invention, there is provided a method for producing a non-aqueous electrolyte secondary battery capable of improving battery performance by generating high-quality SEI (particularly, a uniform film in the thickness direction of the negative electrode active material layer). Can be provided.

1 is a schematic cross-sectional view showing a basic configuration of a non-bipolar flat (stacked) non-aqueous electrolyte lithium ion secondary battery that is a typical embodiment of a non-aqueous electrolyte secondary battery. FIG. 2A is a plan view showing a state in which stripe-shaped adhesive portions are provided on the electrode surface. 32 and 2C are plan views showing a state in which a dot-shaped adhesive portion is provided on the electrode surface. It is a perspective view showing the appearance of a flat lithium ion secondary battery which is a typical embodiment of a secondary battery. FIG. 4 is a drawing showing the process flow of the manufacturing method of the present invention. FIG. 5A is a drawing schematically showing an outline of a slurry preparation apparatus. FIG. 5B is a drawing schematically showing a method for preparing a negative electrode slurry using the slurry preparing apparatus of FIG. 5, and FIG. 5C schematically shows a state of the negative electrode active material in the slurry obtained from FIG. 5B. It is the drawing. FIG. 6A is a schematic cross-sectional view showing the influence of a coating derived from a solvent in an electrolytic solution or gel electrolyte, and FIG. 6B is a schematic cross-sectional view showing the influence of a coating derived from an additive for SEI formation. It is the electrode cross-sectional schematic diagram which represented typically the mode immediately after pouring of electrolyte solution among the SEI formation processes derived from the additive for SEI formation in the electrolyte solution or gel electrolyte of the conventional (patent document 1). It is the electrode cross-sectional schematic which typically represented the mode immediately after the first charge among the SEI formation processes derived from the additive for SEI formation in the electrolyte solution or gel electrolyte of the past (patent document 1). In the conventional (Patent Document 1) electrolyte solution or gel electrolyte, the SEI formation process derived from the SEI formation additive is a schematic cross-sectional view of an electrode schematically showing that SEI has begun to be formed outside the negative electrode by initial charging. is there. In the conventional SEI formation process derived from the SEI formation additive in the electrolyte solution or gel electrolyte (patent document 1), the additive in the electrolyte solution of the positive electrode moves to the negative electrode side and the SEI is also formed on the inner side of the negative electrode. It is an electrode cross-sectional schematic diagram showing typically a mode that it was formed. It is the negative electrode cross-sectional schematic which typically represented the mode at the time of drying a negative electrode slurry among the SEI formation processes derived from the additive for SEI formation in the negative electrode slurry of this invention. It is the electrode cross-sectional schematic which typically represented the mode before injection | pouring of electrolyte solution among the SEI formation processes derived from the additive for SEI formation in the negative electrode slurry of this invention. It is the electrode cross-sectional schematic diagram which represented typically the mode after pouring of electrolyte solution among the SEI formation processes derived from the additive for SEI formation in the negative electrode slurry of this invention. It is the electrode cross-sectional schematic which typically represented the mode after initial charge among the SEI formation processes derived from the additive for SEI formation in the negative electrode slurry of this invention. It is an exploded perspective view showing typically the basic composition of a layered product. It is drawing which represented typically a mode that a laminated body was pinched | interposed (stored) from the upper and lower sides with the laminate film used for a battery exterior body. It is drawing which represented the mode of the 3 side sealing body which accommodated the laminated body in the exterior body, and sealed 3 sides of the exterior body. It is drawing which represented typically the apparatus structure which injects electrolyte solution from the opening part of the 1 side which a 3 side sealing body remains.

  The method for producing a non-aqueous electrolyte secondary battery of the present invention is characterized in that the negative electrode slurry used for forming the negative electrode contains an additive for SEI formation. Preferably, it is desirable that neither the electrolyte solution nor the positive electrode slurry used for positive electrode formation contains an additive for SEI formation. Specifically, the production method of the present invention includes a positive electrode forming step using a positive electrode slurry, a negative electrode forming step using a negative electrode slurry, a positive electrode and a negative electrode obtained in the positive electrode forming step and the negative electrode forming step, a separator, And a step of injecting an electrolytic solution into the laminate placed in the exterior body. The negative electrode slurry contains an additive for forming SEI. Preferably, neither the electrolyte solution nor the positive electrode slurry contains an additive for forming SEI. The nonaqueous electrolyte secondary battery of the present invention is obtained by the above production method. With the manufacturing method of the present invention having such a configuration and the battery obtained thereby, the operational effects of the above-described invention can be achieved.

  First, although a nonaqueous electrolyte lithium ion secondary battery will be described as a preferred embodiment of the nonaqueous electrolyte secondary battery of the present invention, it is not limited to only the following embodiments. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. In addition, the dimensional ratios in the drawings are exaggerated for convenience of explanation, and may be different from the actual ratios.

  When distinguished by the structure and form of the lithium ion secondary battery, it is not particularly limited, such as a stacked (flat) battery or a wound (cylindrical) battery, and can be applied to any conventionally known structure.

  Similarly, there is no particular limitation when distinguished by the form of electrolyte. For example, the present invention can be applied to any of a liquid electrolyte type battery in which a separator is impregnated with a nonaqueous electrolytic solution, a polymer gel electrolyte type battery also called a polymer battery, and a solid polymer electrolyte (all solid electrolyte) type battery. In the present embodiment, as for the polymer gel electrolyte and the solid polymer electrolyte, those obtained by impregnating a separator with the polymer gel electrolyte or the solid polymer electrolyte can be used.

  In the following description, a lithium ion secondary battery that is not a bipolar type (internal parallel connection type) will be described with reference to the drawings. However, the present invention should not be limited to these, and the bipolar type (internal series connection type) lithium ion secondary battery It can also be applied to secondary batteries.

  FIG. 1 is a schematic diagram showing a basic configuration of an embodiment of a flat (stacked) non-aqueous electrolyte lithium ion secondary battery (hereinafter also simply referred to as “stacked battery”) that is not bipolar. As shown in FIG. 1, the stacked battery 10 of the present embodiment has a structure in which a substantially rectangular power generation element 21 in which a charge / discharge reaction actually proceeds is sealed inside a battery exterior material 29 that is an exterior body. Have. Here, the power generation element 21 has a configuration in which a positive electrode, an electrolyte layer 17, and a negative electrode are stacked. The positive electrode has a structure in which the positive electrode active material layer 13 is disposed on both surfaces of the positive electrode current collector 11. The negative electrode has a structure in which the negative electrode active material layers 15 are disposed on both surfaces of the negative electrode current collector 12. Specifically, the negative electrode, the electrolyte layer, and the positive electrode are laminated in this order so that one positive electrode active material layer 13 and the negative electrode active material layer 15 adjacent thereto face each other with the electrolyte layer 17 therebetween. . Thereby, the adjacent positive electrode, electrolyte layer, and negative electrode constitute one unit cell layer 19. Therefore, it can be said that the stacked battery 10 of the present embodiment has a configuration in which a plurality of the single battery layers 19 are stacked and electrically connected in parallel. Note that a bipolar (internal series connection type) lithium-ion secondary battery (stacked structure) has a configuration in which a plurality of single battery layers (single cells) are stacked to be electrically connected in series. It can be said that it has.

  In addition, although the positive electrode active material layer 13 is arrange | positioned only at one side in the outermost layer positive electrode collector located in both outermost layers of the electric power generation element 21, an active material layer may be provided in both surfaces. That is, instead of using a current collector dedicated to the outermost layer provided with an active material layer only on one side, a current collector having an active material layer on both sides may be used as it is as an outermost current collector. In addition, the arrangement of the positive electrode and the negative electrode is reversed from that in FIG. 1, so that the outermost layer negative electrode current collector is positioned on both outermost layers of the power generation element 21, and the outermost layer negative electrode current collector is disposed on one or both surfaces. A negative electrode active material layer may be disposed.

  In the present embodiment, the electrode (positive electrode or negative electrode) includes a self-supporting electrode. A self-supporting electrode secures the shape without a metal foil (current collector). In other words, the self-supporting electrode (self-supporting structure) can be structurally (or strength) secured with only the active material layer without the metal foil (current collector). However, even if it is a self-supporting electrode (self-supporting structure), the electrode element is a current collector (however, other than the metal foil, the mechanical strength is lower than that of the metal foil, and the metal deposited film or plated thin film that cannot secure the shape. In addition, a metal wiring or the like may be required) and an active material layer. The self-supporting electrode defined above includes an active material layer (positive electrode active material layer, negative electrode active material layer) and a current collector (positive electrode current collector, negative electrode current collector) formed directly on one side of the active material layer. And have. The active material layer includes a porous skeleton and an active material (positive electrode active material, negative electrode active material) held in the pores of the porous skeleton.

  In this specification, when it is described as “current collector”, it may refer to both a positive electrode current collector and a negative electrode current collector, or may refer to only one, or for a bipolar electrode of a bipolar battery. Sometimes refers to a current collector. Similarly, when describing as “active material layer”, both the positive electrode active material layer and the negative electrode active material layer may be referred to, or only one of them may be referred to. Similarly, when describing as "active material", both a positive electrode active material and a negative electrode active material may be pointed out, and only one side may be pointed out. Similarly, when describing as "electrode", both a positive electrode and a negative electrode may be pointed out, and only one side may be pointed out.

  The positive electrode current collector 11 and the negative electrode current collector 12 include one of a positive electrode current collector tab (positive electrode current collector plate) 25 and a negative electrode current collector tab (negative electrode current collector plate) 27 that are electrically connected to each electrode (positive electrode and negative electrode). The tip of each is attached. Further, the other end portions of the positive electrode current collecting tab 25 and the negative electrode current collecting tab 27 have a structure of being led out of the battery outer packaging material 29 so as to be sandwiched between the end portions of the battery outer packaging material 29. The positive electrode current collecting tab 25 and the negative electrode current collecting tab 27 are respectively connected to the positive electrode current collector 11 and the negative electrode current collector 11 of each electrode via electrode terminal leads (positive electrode terminal lead and negative electrode terminal lead) (not shown) as necessary. The electric body 12 may be attached by ultrasonic welding, resistance welding, or the like.

  Hereinafter, the stacked battery of the present embodiment will be described in detail for each of the above-described configuration requirements. In addition, about each component (constituent member) of the laminated battery 10, it does not restrict | limit only to the following form, A conventionally well-known form may be employ | adopted similarly.

(1) Current collector The current collector is made of a conductive material, and an active material layer is disposed on one or both surfaces thereof. There is no particular limitation on the material constituting the current collector, and for example, a conductive resin in which a conductive filler is added to a metal or a conductive polymer material or a non-conductive polymer material may be employed.

  Examples of the metal include aluminum, nickel, iron, stainless steel, titanium, and copper. In addition to these, a clad material of nickel and aluminum, a clad material of copper and aluminum, or a plating material of a combination of these metals can be preferably used. Moreover, the foil by which aluminum is coat | covered on the metal surface may be sufficient. Of these, aluminum, stainless steel, and copper are preferable from the viewpoint of conductivity and battery operating potential.

  As a form of the current collector using metal, a metal vapor deposition layer, a metal plating layer, a conductive primer layer, and a metal wiring may be used in addition to the metal foil. The metal vapor deposition layer and the metal plating layer can form (arrange) an extremely thin metal vapor deposition layer or metal plating layer on one surface of the active material layer by a vacuum vapor deposition method or various plating methods. As for the metal wiring, an extremely thin metal wiring can be formed (arranged) on one surface of the active material layer by vacuum vapor deposition or various plating methods. Further, a metal wiring can be impregnated with a primer layer and attached by thermocompression bonding. Furthermore, when a punching metal sheet or an expanded metal sheet is used as the metal wiring, an electrode slurry is applied to both sides of the punching metal sheet or the expanded metal sheet and dried, so that the metal wiring sandwiched between the active material layers (current collector) ) Can be arranged. Even when the metal foil is used, the metal foil (current collector) can be disposed on one side of the active material layer by applying and drying the electrode slurry on the metal foil (one side or both sides). The conductive primer layer is basically prepared by mixing a resin with carbon (chain, fiber) or metal filler (aluminum, copper, stainless steel, nickel powder, etc. used for the current collector material). be able to. The formulation varies. It can be formed (arranged) by applying and drying this on one side of the active material layer.

  The conductive primer layer includes a current collecting adhesive layer having conductivity. Preferably, the conductive primer layer comprises a current collecting adhesive layer having conductivity. In order for the conductive primer layer to have conductivity, specific modes are as follows: 1) the polymer material constituting the resin is a conductive polymer, 2) the current collecting adhesive layer is a resin and a conductive filler (conductive) Material).

  The conductive polymer used in the form 1) is selected from materials having conductivity and not having conductivity with respect to ions used as a charge transfer medium. These conductive polymers are considered to be conductive because the conjugated polyene system forms an energy band. As a typical example, a polyene-based conductive polymer that has been put into practical use in an electrolytic capacitor or the like can be used. Specifically, polyaniline, polypyrrole, polythiophene, polyacetylene, polyparaphenylene, polyphenylene vinylene, polyacrylonitrile, polyoxadiazole, or a mixture thereof is preferable. Polyaniline, polypyrrole, polythiophene, and polyacetylene are more preferable from the viewpoint of electronic conductivity and stable use in the battery.

  The conductive filler (conductive material) used in the form 2) is selected from materials having conductivity. Preferably, from the viewpoint of suppressing ion permeation in the current collecting adhesive layer having conductivity, it is desirable to use a material that does not have conductivity with respect to ions used as the charge transfer medium.

  Specific examples include, but are not limited to, aluminum materials, stainless steel (SUS) materials, carbon materials, silver materials, gold materials, copper materials, and titanium materials. These conductive fillers may be used alone or in combination of two or more. Moreover, these alloy materials may be used. Silver material, gold material, aluminum material, stainless steel material, carbon material is preferable, and carbon material is more preferable. Further, these conductive fillers (conductive materials) may be those obtained by coating a conductive material (the above-mentioned conductive material) around the particle ceramic material or resin material with plating or the like.

  Examples of the carbon material include at least one selected from the group consisting of acetylene black, vulcan, black pearl, carbon nanofiber, ketjen black, carbon nanotube, carbon nanohorn, carbon nanoballoon, hard carbon, and fullerene. Can be mentioned. These carbon materials have a very wide potential window, are stable in a wide range with respect to both the positive electrode potential and the negative electrode potential, and are excellent in conductivity. Also, since the carbon material is very lightweight, the increase in mass is minimized. Furthermore, since carbon materials are often used as conductive aids for electrodes, even if they come into contact with these conductive aids, the contact resistance is very low because of the same material. When carbon materials are used as conductive particles, it is possible to reduce the compatibility of the electrolyte by applying a hydrophobic treatment to the surface of the carbon, making it difficult for the electrolyte to penetrate into the current collector holes. is there.

  The shape of the conductive filler (conductive material) is not particularly limited, and a known shape such as a particle shape, a powder shape, a fiber shape, a plate shape, a lump shape, a cloth shape, or a mesh shape can be appropriately selected. For example, when it is desired to impart conductivity to a resin over a wide range, it is preferable to use a particulate conductive material. On the other hand, when it is desired to further improve the conductivity in a specific direction in the resin, it is preferable to use a conductive material having a certain direction in the shape of a fiber or the like.

  Although the average particle diameter of a conductive filler is not specifically limited, It is desirable that it is about 0.01-10 micrometers. In the present specification, “particle diameter” means the maximum distance L among the distances between any two points on the contour line of the conductive filler. As the value of “average particle diameter”, the average particle diameter of particles observed in several to several tens of fields using an observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). The calculated value shall be adopted. Particle diameters and average particle diameters of active material particles to be described later can be defined similarly.

  In the case where the current collecting adhesive layer contains a conductive filler, the resin forming the current collecting adhesive layer is made of a non-conductive polymer material that binds the conductive filler in addition to the conductive filler. May be included. By using a non-conductive polymer material as the constituent material of the current collecting adhesive layer, the binding property of the conductive filler can be improved and the reliability of the battery can be improved. The polymer material is selected from materials that can withstand the applied positive electrode potential and negative electrode potential.

  Examples of polymer materials having no electrical conductivity are preferably polyethylene (PE), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET), polyethernitrile (PEN), polyimide (PI), polyamide ( PA), polyamideimide (PAI), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), polyacrylonitrile (PAN), polymethyl acrylate (PMA), polymethyl methacrylate (PMMA), polyvinyl chloride (PVC) ), Polyvinylidene fluoride (PVdF), polyvinylidene chloride (PVDC), or mixtures thereof. These materials have a very wide potential window and are stable to both positive and negative electrode potentials. Moreover, since it is lightweight, it becomes possible to increase the output density of the battery.

  The content of the conductive filler is not particularly limited. In particular, when the resin includes a conductive polymer material and sufficient conductivity can be secured, it is not always necessary to add a conductive filler. However, when the resin is made of only a nonconductive polymer material, it is essential to add a conductive filler in order to impart conductivity. The content of the conductive filler at this time is preferably 5 to 90% by mass, more preferably 30 to 85% by mass, and still more preferably 50 to 90% by mass with respect to the total mass of the nonconductive polymer material. 80% by mass. By adding such an amount of conductive filler to the resin, sufficient conductivity can be imparted to the non-conductive polymer material while suppressing an increase in the mass of the resin.

  The conductive primer layer may contain other additives in addition to the conductive filler and the resin, but preferably includes the conductive filler and the resin.

  Among the materials constituting the current collector, examples of the conductive polymer material include polyaniline, polypyrrole, polythiophene, polyacetylene, polyparaphenylene, polyphenylene vinylene, polyacrylonitrile, and polyoxadiazole. . Since such a conductive polymer material has sufficient conductivity without adding a conductive filler, it is advantageous in terms of facilitating the manufacturing process or reducing the weight of the current collector.

  Examples of non-conductive polymer materials include polyethylene (PE; high density polyethylene (HDPE), low density polyethylene (LDPE)), polypropylene (PP), polyethylene terephthalate (PET), polyether nitrile (PEN), polyimide ( PI), polyamideimide (PAI), polyamide (PA), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), polyacrylonitrile (PAN), polymethyl acrylate (PMA), polymethyl methacrylate (PMMA), Examples include polyvinyl chloride (PVC), polyvinylidene fluoride (PVdF), and polystyrene (PS). Such a non-conductive polymer material may have excellent potential resistance or solvent resistance.

  A conductive filler may be added to the conductive polymer material or the non-conductive polymer material as necessary. In particular, when the resin used as the base material of the current collector is made of only a non-conductive polymer, a conductive filler is inevitably necessary to impart conductivity to the resin. The conductive filler can be used without particular limitation as long as it is a substance having conductivity. For example, metals, conductive carbon, etc. are mentioned as a material excellent in electroconductivity, electric potential resistance, or lithium ion barrier | blocking property. The metal is not particularly limited, but at least one metal selected from the group consisting of Ni, Ti, Al, Cu, Pt, Fe, Cr, Sn, Zn, In, Sb, and K, or these metals. It is preferable to include an alloy or metal oxide. Further, the conductive carbon is not particularly limited, but is at least one selected from the group consisting of acetylene black, vulcan, black pearl, carbon nanofiber, ketjen black, carbon nanotube, carbon nanohorn, carbon nanoballoon, and fullerene. Preferably it contains seeds. The amount of the conductive filler added is not particularly limited as long as it is an amount capable of imparting sufficient conductivity to the current collector, and is generally about 5 to 35% by mass.

  The size of the current collector is determined according to the intended use of the battery. For example, if it is used for a large battery that requires a high energy density, a current collector having a large area is used.

  The thickness of the current collector is preferably 1 to 100 μm, more preferably 3 to 80 μm, and still more preferably 5 to 40 μm. Since the self-standing electrode can be thinned, it is preferably 1 to 18 μm, more preferably 2 to 15 μm, and further preferably 3 to 13 μm. This can be produced without going through a conventional coating / drying process when producing a free-standing electrode. Therefore, when a current collector is used for a metal vapor deposition layer, metal plating layer, conductive primer layer or metal wiring that does not need to undergo the conventional coating / drying process, the tension required in the coating / drying process is required. There is no need to have strength. Accordingly, the thickness of the current collector can be reduced as necessary, and the degree of freedom in designing the current collector is improved, which contributes to the weight reduction of the electrodes, and hence the battery.

  When using a punching metal sheet or an expanded metal sheet having a plurality of through holes as a current collector, the through holes have a quadrilateral shape, rhombus shape, turtle shell shape, hexagonal shape, round shape, square shape, star shape, cross shape, etc. Examples include shapes. A so-called punching metal sheet or the like is formed by pressing a large number of holes having such a predetermined shape, for example, in a staggered arrangement or a parallel arrangement. A so-called expanded metal sheet or the like is formed by stretching a sheet with staggered cuts to form a large number of substantially diamond-shaped through holes.

  When the current collector having the plurality of through holes described above is used for the current collector, the aperture ratio of the through holes of the current collector is not particularly limited. However, the lower limit of the aperture ratio of the current collector is preferably 10 area% or more, more preferably 30 area% or more, further preferably 50 area% or more, more preferably 70 area% or more, and further preferably 90 area. % Or more. Thus, in the electrode of this embodiment, a current collector having an aperture ratio of 90 area% or more can also be used. Moreover, as an upper limit, it is 99 area% or less, or 97 area% or less, for example. As described above, the stacked structure battery 10 including the electrodes formed with the current collector having a significantly large aperture ratio can significantly reduce the weight, and thus can increase the capacity. The density can be increased.

  When the current collector having the plurality of through holes is used as the current collector, the diameter (opening diameter) of the through holes of the current collector is not particularly limited as well. However, the lower limit of the opening diameter of the current collector is preferably 10 μm or more, more preferably 20 μm or more, still more preferably 50 μm or more, and particularly preferably 150 μm or more. As an upper limit, it is 300 micrometers or less, for example, Preferably, it is about 200 micrometers or less. In addition, the opening diameter here is the diameter of the circumscribed circle of the through hole = opening. The diameter of the circumscribed circle is obtained by observing the surface of the current collector with a laser microscope or a tool microscope, fitting the circumscribed circle to the opening, and averaging the results.

(2) Electrode (Positive Electrode and Negative Electrode) and Electrode Active Material Layer The positive electrode and the negative electrode have a function of generating electric energy by transferring lithium ions. The positive electrode essentially includes a positive electrode active material, and the negative electrode essentially includes a negative electrode active material.

  In particular, in the present invention, regardless of the thickness direction of the negative electrode active material layer, the surface of the negative electrode active material particles has high quality (uniform thickness) SEI derived from the additive for SEI formation. In the negative electrode active material layer obtained by the production method of the present invention, the negative electrode active material surface near the negative electrode current collector inside the electrode and the negative electrode active material surface near the outside of the electrode (negative electrode active material layer) This is to prevent the problem that the thickness of the SEI formed at the first charge is different (refer to FIGS. 7 to 10 and FIGS. 11 to 14). One purpose of the initial charging step is to form SEI on the surface of the negative electrode active material particles. By using the negative electrode slurry containing the additive for SEI formation, the additive in the liquid electrolyte or gel electrolyte on the positive electrode side is not included at the time of the initial charge. Since it does not need to be formed and does not need to follow a complicated process, the initial charge time can be shortened, and an inexpensive negative electrode and thus a battery can be provided with high production efficiency. Further, as shown in FIG. 4, it is not necessary to perform high temperature aging over 14 days or more after the first charge, and further room temperature aging for 14 days or more, and there is no problem of quality variation as shown in FIG. Therefore, it is possible to provide a high-quality and more inexpensive negative electrode, and thus a battery.

  Further, in the present invention, it is desirable that the positive electrode active material layer does not contain an additive for SEI formation. Thereby, the negative electrode active material surface in the vicinity of the negative electrode current collector inside the electrode and the negative electrode active material surface in the vicinity of the electrode (negative electrode active material layer) outside do not cause a problem that the thickness of the formed SEI is different. (For comparison, see FIGS. 7 to 10 and FIGS. 11 to 14). One purpose of the initial charging process is the formation of SEI. When an additive for forming SEI is included in the positive electrode active material layer, it is necessary to form SEI after the additive side in the positive electrode active material layer is dissolved in the electrolytic solution and moved to the negative electrode side during the initial charge. In order to follow a complicated process, the first charge time becomes longer. Further, after that, as shown in FIG. 4, although it is necessary to perform high temperature aging over 14 days or more, and room temperature aging for 14 days or more, there is a problem that quality variation occurs as shown in FIG. there were. In this invention, since it is a battery structure obtained by the manufacturing method which adds the additive for SEI formation to a negative electrode slurry, and does not add to electrolyte solution and a positive electrode slurry, it is excellent at the point which can eliminate the above-mentioned subject.

  In the case of a laminated battery, these electrode structures are structures in which an active material layer containing an active material is formed on the surface of the current collector as shown in FIG. On the other hand, in the case of a bipolar secondary battery (bipolar electrode), a positive electrode active material layer containing a positive electrode active material is formed on one surface of a current collector, and a negative electrode active material containing a negative electrode active material on the other surface. It has a structure in which a material layer is formed. That is, the positive electrode (positive electrode active material layer) and the negative electrode (negative electrode active material layer) are integrated with each other through the current collector. In addition to the active material, the active material layer may contain a conductive additive, a binder, and an additive such as an electrolyte salt (lithium salt) or an ion conductive polymer as an electrolyte as necessary. In addition, in the negative electrode, when the negative electrode slurry using an aqueous solvent is used, in addition to the above, additives such as an aqueous binder and a thickener (such as CMC) can be included.

(2a) Positive electrode active material As a positive electrode active material, a conventionally well-known thing can be used.

Examples of the positive electrode active material include LiMn ₂ O ₄ , LiCoO ₂ , LiNiO ₂ , Li (Ni, Co, Mn) O ₂ , Li ₂ MnO ₃ , Li ₂ MnO ₃ —LiMO ₂ (M = Co, Ni, etc.) ) Lithium-transition metal composite oxides such as solid solutions and those in which some of these transition metals are substituted with other elements, lithium-transition metal phosphate compounds, lithium-transition metal sulfate compounds, and the like. In some cases, two or more positive electrode active materials may be used in combination. Preferably, a lithium-transition metal composite oxide is used as the positive electrode active material from the viewpoint of capacity and output characteristics. Of course, positive electrode active materials other than those described above may be used. In addition, a positive electrode active material having a high energy density such as LiNiO ₂ , Li (Ni, Co, Mn) O ₂ , or Li ₂ MnO ₃ is easy to increase the capacity of the battery. It is also advantageous in that the travel distance can be extended.

  The average particle size of the positive electrode active material is not particularly limited, but is preferably 1 to 25 μm from the viewpoint of increasing the output.

  The amount of the positive electrode active material is not particularly limited, but is preferably 50 to 99% by mass, more preferably 70 to 97% by mass, and still more preferably 80 to 96%, based on the total amount of the positive electrode active material layer (forming raw material). It is the range of mass%.

(2b) Negative electrode active material A negative electrode active material has a composition which can discharge | release lithium ion at the time of discharge and can occlude lithium ion at the time of charge. The negative electrode active material is not particularly limited as long as it can reversibly occlude and release lithium. Examples of the negative electrode active material include metals such as Si and Sn, TiO, Ti ₂ O ₃ , TiO ₂ , or Metal oxides such as SiO ₂ , SiO, SnO ₂ , complex oxides of lithium and transition metals such as Li _4/3 Ti _5/3 O ₄ or Li ₇ MnN, Li—Pb alloys, Li—Al alloys , Li, or carbon materials such as natural graphite, artificial graphite, carbon black, activated carbon, carbon fiber, coke, soft carbon, or hard carbon. Among these, by using an element that forms an alloy with lithium, it becomes possible to obtain a battery having a high capacity and an excellent output characteristic having a higher energy density than that of a conventional carbon-based material. The negative electrode active material may be used alone or in the form of a mixture of two or more. The element alloying with lithium is not limited to the following, but specifically, Si, Ge, Sn, Pb, Al, In, Zn, H, Ca, Sr, Ba, Ru, Rh, Ir, Pd, Pt, Ag, Au, Cd, Hg, Ga, Tl, C, N, Sb, Bi, O, S, Se, Te, Cl, and the like.

  Among the active materials, it preferably contains a carbon material and / or at least one element selected from the group consisting of Si, Ge, Sn, Pb, Al, In, and Zn. Or it is more preferable that the element of Sn is included. Of the carbon materials, it is more preferable to use graphite having a low lithium relative discharge potential.

  When the negative electrode active material is used as a negative electrode, the negative electrode active material layer containing the negative electrode active material may be formed into a plate shape and used as it is, or the negative electrode active material containing the negative electrode active material particles on the surface of the current collector. A material layer may be formed to form a negative electrode. The average particle diameter of the negative electrode active material particles in the latter form is not particularly limited, but is preferably 1 to 100 μm from the viewpoint of high capacity, reactivity, and cycle durability of the negative electrode active material, and further increase the output. From the viewpoint, the thickness is more preferably 1 to 25 μm. Within such a range, the secondary battery can suppress an increase in the internal resistance of the battery during charging and discharging under high output conditions, and can extract a sufficient current. In addition, when the negative electrode active material is secondary particles, it can be said that the average particle diameter of primary particles constituting the secondary particles is desirably in the range of 10 nm to 1 μm. It is not limited to. However, it goes without saying that, depending on the manufacturing method, the negative electrode active material may not be a secondary particle formed by aggregation, lump or the like. As the particle size of the negative electrode active material and the particle size of the primary particles, the median diameter obtained using a laser diffraction method can be used. The shape of the negative electrode active material particles varies depending on the type and manufacturing method, and examples thereof include a spherical shape (powdered shape), a plate shape, a needle shape, a column shape, and a square shape, but are not limited thereto. Any shape can be used without any problem. Preferably, an optimal shape that can improve battery characteristics such as charge / discharge characteristics is appropriately selected.

  The amount of the negative electrode active material is not particularly limited, but is preferably 50 to 99% by mass, more preferably 70 to 97% by mass, and still more preferably 80 to 96%, based on the total amount of the negative electrode active material layer (forming raw material). It is the range of mass%.

(2b) Conductive aid The conductive aid refers to an additive blended to improve the conductivity of the active material layer. Examples of the conductive aid include carbon powders such as acetylene black, carbon black, ketjen black, and graphite, various carbon fibers such as vapor grown carbon fiber (VGCF; registered trademark), expanded graphite, and the like. However, it goes without saying that the conductive aid is not limited to these. When the active material layer contains a conductive additive, an electronic network inside the active material layer is effectively formed, which can contribute to improvement of the output characteristics of the battery. However, in the case where a carbon material that is a conductive material is used as the active material, an electronic network can be effectively formed only by the active material, and if the conductive material contributes to the improvement of the output characteristics of the battery, a conductive auxiliary agent is not added. Also good.

  The content of the conductive additive mixed in the positive electrode active material layer is 1% by mass or more, more preferably 3% by mass or more, and further preferably 5% by mass with respect to the total amount of the positive electrode active material layer (formation raw material). % Or more. In addition, the content of the conductive additive mixed into the positive electrode active material layer is 15% by mass or less, more preferably 10% by mass or less, further preferably, with respect to the total amount of the positive electrode active material layer (formation raw material). It is the range of 7 mass% or less. By defining the compounding ratio (content) of the conductive auxiliary agent in the positive electrode active material layer within the above range, the electronic conductivity of the active material itself is low and the electrode resistance can be reduced by the amount of the conductive auxiliary agent. Is done. That is, it is possible to sufficiently ensure the electronic conductivity without hindering the electrode reaction, to suppress the decrease in the energy density due to the decrease in the electrode density, and to improve the energy density due to the increase in the electrode density. .

The content of the conductive additive mixed into the negative electrode active material layer cannot be uniquely defined because it varies depending on the negative electrode active material. That is, when a carbon material such as graphite (graphite), soft carbon, hard carbon, or a metal material is used, in which the negative electrode active material itself has excellent electronic conductivity, the inclusion of the conductive assistant in the negative electrode active material layer is There is no particular need. Even if it contains a conductive additive, a range of 0.1 to 1% by mass at most is sufficient with respect to the total amount of the electrode constituting material on the negative electrode side. On the other hand, like the positive electrode active material, the electronic conductivity is low, and the electrode resistance can be reduced by the amount of the conductive auxiliary. In the case of using a negative electrode active material such as a lithium alloy negative electrode material or a lithium-transition metal composite oxide (for example, Li ₄ Ti ₅ O ₁₂ ), the content of the conductive additive mixed in the positive electrode active material layer and It is desirable to have the same content. That is, the content of the conductive additive mixed in the negative electrode active material layer is also preferably 1 to 10% by mass, more preferably 2 to 8% by mass, particularly preferably relative to the total amount of the electrode constituent material on the negative electrode side. Is preferably in the range of 3 to 7% by mass.

(2c) Binder (binder)
The binder is added for the purpose of maintaining the electrode structure by binding the constituent members in the active material layer or the active material layer and the current collector. The binder is not particularly limited as long as it is an insulating material that can achieve the above-described purpose and does not cause a side reaction (oxidation-reduction reaction) at the time of charge / discharge, and examples thereof include the following materials. Polyethylene, polypropylene, polyethylene terephthalate (PET), polyether nitrile, polyacrylonitrile, polyimide, polyamide, cellulose, carboxymethyl cellulose (CMC), ethylene-vinyl acetate copolymer, polyvinyl chloride, styrene-butadiene rubber (SBR), isoprene Rubber, butadiene rubber, ethylene / propylene rubber, ethylene / propylene / diene copolymer, styrene / butadiene / styrene block copolymer and its hydrogenated product, styrene / isoprene / styrene block copolymer and its hydrogenated product, etc. Thermoplastic polymer, polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), Tet Fluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), ethylene / tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), ethylene / chlorotrifluoroethylene copolymer (ECTFE), polyfluorinated Fluorine resin such as vinyl (PVF), vinylidene fluoride-hexafluoropropylene-based fluororubber (VDF-HFP-based fluororubber), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene-based fluororubber (VDF-HFP-TFE-based fluorine) Rubber), vinylidene fluoride-pentafluoropropylene-based fluoro rubber (VDF-PFP-based fluoro rubber), vinylidene fluoride-pentafluoropropylene-tetrafluoroethylene-based fluoro rubber (VDF-PFP-TFE fluorine rubber), vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene fluorine rubber (VDF-PFMVE-TFE fluorine rubber), vinylidene fluoride-chlorotrifluoroethylene fluorine rubber (VDF) Vinylidene fluoride fluororubbers such as (-CTFE fluororubber) and epoxy resins. Among these, polyvinylidene fluoride, polyimide, styrene / butadiene rubber, carboxymethyl cellulose, polypropylene, polytetrafluoroethylene, polyacrylonitrile, and polyamide are more preferable. These suitable binders are excellent in heat resistance, have a very wide potential window, are stable at both the positive electrode potential and the negative electrode potential, and can be used for the active material layer. These binders may be used independently and may use 2 or more types together. However, it goes without saying that the binder is not limited to these.

  The amount of the binder is not particularly limited as long as it can bind the electrode (positive electrode, negative electrode) active material and the like, but preferably the electrode (positive electrode, negative electrode) active material layer (or its formation) It is 0.5-15 mass% with respect to the total amount of a raw material), More preferably, it is 1-10 mass%.

(2d) Electrolyte salt (lithium salt)
As the electrolyte salt (lithium _{salt), LiPF 6, LiBF 4,} LiClO 4, LiAsF 6, LiTaF 6, LiAlCl 4, Li 2 B 10 C l10, LiCF 3 SO 3, Li (CF 3 SO 2) 2 N, Li (C ₂ F ₅ SO ₂ ) ₂ N, bispentafluoroethylsulfonylimide lithium (LiBETI), and the like can be given. Furthermore, an electrolyte salt (lithium salt) used for an electrolyte layer described later can be appropriately used. The compounding ratio of the electrolyte salt (lithium salt) contained in the electrode active material layer is not particularly limited. The mixing ratio can be adjusted by appropriately referring to known knowledge about non-aqueous solvent secondary batteries.

(2e) Ion conductive polymer Examples of the ion conductive polymer include polyethylene oxide (PEO) -based polymers, polypropylene oxide (PPO) -based polymers, and ion-conductive polymers (solids) that can include lithium salts of these copolymers. Polymer electrolyte material). Furthermore, an electrolyte salt (lithium salt) used for an electrolyte layer described later can be appropriately used. The compounding ratio of the ion conductive polymer contained in the electrode active material layer is not particularly limited. The mixing ratio can be adjusted by appropriately referring to known knowledge about non-aqueous solvent secondary batteries.

(2f) Thickener or carboxymethylcellulose (CMC) derivative When an aqueous slurry containing an aqueous solvent is used for producing the negative electrode, the negative electrode active material, the thickener or CMC derivative, the aqueous binder in the negative electrode active material including. Preferably, an alkali metal and / or an alkaline earth metal and an alkali carbonate are further contained. If necessary, other additives are further included. Among these, the negative electrode active material is as already described.

In addition to the carboxylmethyl group (—CH ₂ COOH), the CMC or CMC salt of the thickener includes —CH ₂ COONa, —CH ₂ COOLi, —CH ₂ COOK, —CH _{2 in} addition to the carboxylmethyl group (—CH ₂ COOH). COONH ₄ etc. exist. As CMC or CMC salt including such a large number of types (compounds), many types (compounds) are already commercially available, and can be appropriately selected from these. Many of these commercially available products are those in which some or all of the hydrogen atoms of the —CH ₂ COOH group in the molecule are cationic species such as Na, Li, K, NH _4, etc., and are cationic species. The amounts of Na, Li, K, and NH ₄ can be arbitrarily adjusted. In this embodiment, micelles are formed at a portion of Na, which is a cationic species such as —CH ₂ COONa, and therefore it can be said that it is desirable to use a cationic species such as Na at the end of the molecular chain of CMC or CMC salt.

As the CMC derivative, all or part of the —CH ₂ COOR group present in the molecule of the CMC or CMC salt of the thickener is a —CH ₂ CHO group, a —CH ₂ CH ₂ OH group, a —CH ₃ group. Some of them are listed here. Here, the —CH ₂ COOR group present in the molecule of the CMC or CMC salt may be one type or two or more types. In the case of one type, R of the —CH ₂ COOR group present in the molecule includes any one of cationic species such as Na, Li, K, and NH ₄ . In the case of two or more species, it is sufficient that R of the —CH ₂ COOR group present in the molecule contains at least a cationic species such as Na, Li, K, NH _4, etc. It may have a hydrogen atom). By containing a CMC derivative instead of CMC or CMC salt as a constituent material of the negative electrode active material layer before the initial charge, the -CH ₂ COOR group present in the molecule is not easily reduced and decomposed by the initial charge. A —CH ₂ CHO group, a —CH ₂ CH ₂ OH group, or a —CH ₃ group. Therefore, reductive decomposition of CMC or CMC salt at the initial charge can be suppressed, and a negative electrode having excellent capacity by improving not only gas generation but also charge / discharge efficiency can be provided.

In the CMC derivative, all or a part of —CH ₂ COOR groups (ionized in an aqueous slurry and present in the state of CH ₂ COO ⁻ (ionic groups)) present in the molecule of CMC or CMC salt are reduced, It is a stable —CH ₂ CHO group, —CH ₂ CH ₂ OH group, or —CH ₃ group. The reduction ratio of —CH ₂ COOR groups (CH ₂ COO ⁻ ionized in an aqueous slurry) present in the molecule of CMC or CMC salt is 10 to 100%, preferably 50 to 100%, more preferably 80 to 100%, particularly preferably 100%. If the reduction ratio is less than 10%, it may be difficult to sufficiently suppress gas generation when the obtained CMC derivative is charged for the first time. By setting it to 10% or more, preferably 50% or more, more preferably 80% or more, gas generation when the obtained CMC derivative is initially charged can be sufficiently suppressed. Therefore, it can be said that the reduction ratio of the —CH ₂ COOR group (CH ₂ COO ^— group) is not necessarily all (= 100%), but by setting the reduction ratio to 100%, the obtained CMC derivative was charged for the first time. The generation of gas at the time can be remarkably suppressed. Moreover, it can be said that it is preferable also in that it can greatly contribute to the capacity improvement. The reduction ratio can be measured for each CMC derivative using surface ESCA (X-ray photoelectron spectroscopy (apparatus)) or the like. In addition, it can also be measured (supplemented) using a COSY (Correlated Spectroscopy Y, Correlated Spectroscopy Y) measurement method using ¹ H NMR (nuclear magnetic resonance spectroscopy), ¹⁴ C NMR, two-dimensional NMR, or the like. Note that the intended purpose and effect of the present invention can be achieved as long as the content of alkali metal and / or alkaline earth metal described later is satisfied instead of the reduction ratio. Therefore, it is possible to achieve the intended object and effect of the present invention by measuring the content of alkali metal and / or alkaline earth metal without purchasing the above-mentioned expensive apparatus and determining the reduction ratio. Since it can be confirmed, the reduction ratio is an arbitrary requirement.

  The content of the thickener or CMC derivative contained in the negative electrode active material layer formed using the negative electrode slurry using the aqueous solvent is 0.1 to 10% by mass, preferably with respect to the total amount of the negative electrode active material layer. Is in the range of 0.5-2% by weight. When the content of the CMC derivative is 0.1% by mass or more, the thickening effect in the negative electrode production process is sufficiently exhibited, and the negative electrode active material layer having a flat and smooth surface can be obtained. In addition, reductive decomposition of CMC or CMC salt in the initial charging of the obtained negative electrode can be suppressed, and a negative electrode having excellent capacity not only by gas generation but also by improvement of charge / discharge efficiency can be provided. Moreover, if content of a CMC derivative is 10 mass% or less, the viscosity of an aqueous | water-based negative electrode slurry can be appropriately adjusted with the outstanding thickening effect, and it can be set as a desired negative electrode active material layer. In addition, reductive decomposition of CMC or CMC salt in the initial charging of the obtained negative electrode can be suppressed, and a negative electrode having excellent capacity not only by gas generation but also by improvement of charge / discharge efficiency can be provided.

  The weight average molecular weight of the thickener or CMC derivative is in the range of 5000 to 1200000, preferably 6000 to 1100000, more preferably 7000 to 1000000. When the weight average molecular weight of the CMC derivative is 5000 or more, the viscosity of the negative electrode aqueous slurry can be kept moderate. For example, when the CMC or CMC salt of the thickener before the CMC derivative is reduced is dissolved in water. The viscosity of the aqueous slurry of the negative electrode can be kept moderate. As a result, it is advantageous in that it can be effectively used as a thickener in the production stage of the negative electrode. If the CMC derivative has a weight average molecular weight of 1200000 or less, the CMC or CMC salt of the thickener before the reduction of the CMC derivative is dissolved in an aqueous solvent such as water, and the negative aqueous system The viscosity of the slurry can be kept moderate. As a result, it is advantageous in that it can be effectively used as a thickener in the production stage of the negative electrode. As a method for measuring the weight average molecular weight of the CMC derivative, for example, the molecular weight distribution of the CMC derivative is measured using gel permeation chromatography using a solvent containing a metal-amine complex and / or a metal-alkali complex as a mobile phase solvent. Measurements can be made. From the molecular weight distribution, the molecular weight of the weight average molecular weight of the CMC derivative can be calculated. In addition, as a measuring method of the weight average molecular weight of a CMC derivative, it does not restrict | limit at all to the said method, It can measure and calculate by a conventionally well-known method.

(2g) Aqueous binder An aqueous binder means a binder that can be uniformly dispersed in an aqueous solvent. Note that a binder used for manufacturing a positive electrode is simply referred to as a binder and is distinguished. The binder used for producing the positive electrode means a binder that can be uniformly mixed (dissolved) or dispersed in an organic solvent.

  Examples of the aqueous binder contained in the negative electrode active material layer formed using the negative electrode slurry using an aqueous solvent include styrene / butadiene rubber (SBR), isoprene rubber, butadiene rubber, ethylene / propylene rubber, nitrile rubber (or nitrile butadiene). Rubber; NBR), ethylene-propylene-diene rubber (EPDM), acrylate rubber, styrene / butadiene / styrene block copolymer and its hydrogenated product, rubber system such as styrene / isoprene / styrene block copolymer and its hydrogenated product A binder can also be used. Furthermore, polyethylene (PE), polypropylene (PP), polytetrafluoroethylene (PTFE), polyethylene terephthalate (PET), polyether nitrile (PEN), polyacrylonitrile, polyimide, polyamide, cellulose, ethylene-vinyl acetate copolymer, Examples thereof include water-based binders such as polyvinyl chloride, polyacrylate, polyvinyl alcohol, methyl cellulose, hydroxyethyl cellulose, polyethylene oxide, and polyethylene glycol. Among these, polyimide, styrene / butadiene rubber, polypropylene, polytetrafluoroethylene, polyacrylonitrile, and polyamide are more preferable. These suitable aqueous binders are excellent in heat resistance, have a very wide potential window, are stable at both the positive electrode potential and the negative electrode potential, and can be used for the negative electrode active material layer. These aqueous binders may be used alone or in combination of two or more. However, the present embodiment is not limited to those exemplified above, and various conventionally known aqueous binders can be used. These are used in a state where the aqueous binder is dispersed in the form of particles in an aqueous solvent such as inexpensive water at the time of manufacturing the electrode. By using these water-based binders, as compared with the case where they are dissolved (mixed or dispersed) in an expensive organic solvent such as NMP, such as conventional organic solvent-based binders such as polyvinylidene fluoride (PVDF), it is low. Cost can be reduced. Furthermore, it is desirable from the viewpoints of low thermal decomposition calorific value at the time of charge, easy to obtain high capacity, and excellent cycle characteristics. Although these water-based binders have strong binding properties (binding effects), they are not sufficiently thickened. Therefore, a sufficient thickening effect cannot be obtained only by adding an aqueous binder to the aqueous slurry at the time of electrode preparation. Therefore, CMC or CMC salt excellent in thickening is used as a thickening agent to impart thickening to the aqueous binder.

  The content of the aqueous binder is not particularly limited as long as it is an amount capable of binding the negative electrode active material and the like, but preferably 0.5 to 15% by mass with respect to the total amount of the negative electrode active material layer. More preferably, it is 1-10 mass%. However, even if it is out of the above range, it can be sufficiently applied as long as the effects of the present invention can be effectively expressed. If the content of the aqueous binder is 0.5% by mass or more, a sufficient binding effect can be obtained by coating and drying using the aqueous slurry, and the negative electrode active material layers or the negative electrodes are obtained in the obtained negative electrode active material layer. The active material and the current collector can be bound to form a conductive three-dimensional network. In addition, reductive decomposition of CMC or CMC salt at the first charge can be suppressed, and a negative electrode having excellent capacity not only by gas generation but also by improvement of charge / discharge efficiency can be provided. Further, if the content of the aqueous binder is 15% by mass or less, the amount of the aqueous binder in the negative electrode active material layer can be sufficiently suppressed, the reductive decomposition of CMC or CMC salt in the first charge can be suppressed, and the gas generation In addition, it is possible to provide a high-capacity negative electrode by improving charge / discharge efficiency. In addition, a sufficient binding (binder) effect is achieved by coating and drying using an aqueous slurry, and in the obtained negative electrode active material layer, the negative electrode active materials are bonded to each other, and a highly conductive three-dimensional network is obtained. Can be formed.

(2h) Alkali metal and / or alkaline earth metal The alkali metal and / or alkaline earth metal contained in the negative electrode active material layer using the aqueous slurry can improve the charge / discharge capacity. The alkali metal and / or alkaline earth metal is not particularly limited, and examples thereof include Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, and Ba. It is not limited. These may be used alone or in combination of two or more.

  Content of an alkali metal and / or alkaline-earth metal is 50-30000 ppm with respect to the total amount of a negative electrode active material layer, Preferably it is the range of 100 ppm-20000 ppm. However, even if it is out of the above range, it can be sufficiently applied as long as the effects of the present invention can be effectively expressed. When the content of the alkali metal and / or alkaline earth metal is 50 ppm or more, an effective content effect for improving the charge / discharge capacity is recognized. Moreover, if it is 30000 ppm or less, it is advantageous at the point which can contribute to the improvement of charging / discharging capacity.

  The alkali metal and / or alkaline earth metal in the negative electrode active material layer formed using the negative electrode slurry using the aqueous solvent is brought into the negative electrode active material layer by adding alkali or alkaline water during the negative electrode manufacturing process. It is a component. Specifically, a negative electrode active material layer containing an element such as lithium, calcium, magnesium, sodium, or potassium can be obtained by reducing CMC or CMC salt by using alkaline water in the negative electrode manufacturing stage. These may exist in the form of oxides (lithium oxide, potassium oxide), carbonates (for example, lithium carbonate, potassium carbonate) and the like, as will be described later.

(2i) Alkali carbonate The negative electrode active material layer formed using a negative electrode slurry using an aqueous solvent preferably contains an alkali carbonate (Li ₂ CO ₃ ). Specifically, by including alkali carbonate in the negative electrode active material layer using an aqueous slurry, reductive decomposition of CMC or CMC salt at the first charge can be significantly suppressed, not only suppressing gas generation, An excellent negative electrode with significantly improved charge / discharge efficiency can be provided. Furthermore, it is also excellent in that the efficiency of the first charge / discharge is improved (see Examples). The alkali carbonate is also a component brought into the negative electrode active material layer by reaction with carbon dioxide in the atmosphere (or aqueous slurry) by adding alkali or alkaline water during the negative electrode manufacturing process.

  The alkali carbonate is not particularly limited, and examples include lithium carbonate, sodium carbonate, potassium carbonate, rubidium carbonate, cesium carbonate, beryllium carbonate, magnesium carbonate, calcium carbonate, strontium carbonate, barium carbonate, and ammonium carbonate. However, it is not limited to these. These may be used alone or in combination of two or more. Of these, lithium carbonate is preferred. In this case, lithium carbonate can be scattered on the surface of the CMC derivative coating, or a lithium carbonate coating can be formed. Since this lithium carbonate is also a component of the SEI (surface film) of the negative electrode active material, it is excellent in that the life performance can be improved in addition to the gas generation suppressing effect and the capacity increasing effect. Scattering of lithium carbonate on the surface of the coating of the CMC derivative or coating of lithium carbonate may be performed by initial charge / discharge as well as during the production of the negative electrode.

  As content of alkali carbonate, it is preferable to set it as the range of 0.01-5 mass% with respect to the total amount of a negative electrode active material layer. However, even if it is out of the above range, it can be sufficiently applied as long as the effects of the present invention can be effectively expressed. If the alkali carbonate content is 0.01% by mass or more, a lithium carbonate coating 37 can be formed on the surface of the negative film 36 of the CMC derivative. Therefore, in addition to the effect of suppressing gas generation and the effect of increasing the capacity, it is excellent in that the life performance can be improved. On the other hand, if the alkali carbonate content is 5 mass% or less, the lithium carbonate coating 37 is formed on the surface of the negative film 36 of the CMC derivative while maintaining a high capacity without reducing the content of the negative electrode active material. It can be formed. Therefore, in addition to the effect of suppressing gas generation and the effect of increasing capacity, it is possible to improve the life performance.

(2j) Other additives In addition to the negative electrode active material, CMC derivative, aqueous binder, alkali metal and / or alkaline earth metal, the negative electrode active material layer formed using the negative electrode slurry using the aqueous solvent includes It is preferable that other additives (for example, conductive assistant, electrolyte salt (lithium salt), ion conductive polymer, etc.) are retained. These conductive assistants, electrolyte salts (lithium salts), and ion conductive polymers are also as already described.

(2k) Porous skeleton used for self-supporting electrode As the porous skeleton used for the self-supporting electrode, non-woven fabric, woven fabric, metal foam (or metal porous material), carbon paper and the like are desirable. Among these, the nonwoven fabric used for the porous skeleton is formed by overlapping fibers in different directions. A resin material is used for the nonwoven fabric, and fibers such as polypropylene, polyethylene, polyethylene terephthalate, cellulose, nylon, EVA resin (ethylene-vinyl acetate copolymer resin), and the like can be applied. Examples of the porous skeleton body other than the nonwoven fabric include resin woven fabric (regular resin porous body), metal foam or metal porous body, and carbon paper. Here, examples of the resin used for the woven fabric made of resin include polypropylene, polyethylene, polyethylene terephthalate, EVA resin, and the like, but are not limited thereto. Preferred examples of the metal foam or metal porous body include, but are not limited to, at least one metal foam or metal porous body of Cu, Ni, Al, and Ti. Preferably, it is a nonwoven fabric made of at least one metal porous body of Cu and Al, carbon paper, polypropylene, polyethylene, and EVA resin.

  The proportion of the porous skeleton in the skeleton part in the active material layer is in the range of 2% by volume or more, preferably 7% by volume or more. On the other hand, the proportion of the porous skeleton in the skeleton part in the active material layer is 28% by volume or less, preferably 12% by volume or less. If the ratio of the porous skeleton in the active material layer is within the above range, the electrode reaction is not hindered.

  The porosity (porosity) of the porous skeleton is preferably 70% to 98%, more preferably 90 to 95%. If it is in the said range, it is excellent in the point from which the effect of invention is acquired effectively.

  The pore size of the porous skeleton is preferably about 50 to 100 μm that can be sufficiently filled with active materials used in the world. If it is in the said range, it is excellent in the point from which the effect of invention is acquired effectively. That is, if the pore size of the porous skeleton is 100 μm or less, the effect of the present embodiment can be obtained effectively. If the pore size is 50 μm or more, the particle size of the active material to be used can be used without any restrictions. Accordingly, it is excellent in that an appropriate active material can be appropriately selected.

  The thickness of the porous skeleton need only be smaller than the thickness of the active material layer, and is usually about 1 to 120 μm, preferably about 1 to 20 μm.

  Although there is no restriction | limiting in particular also about the thickness of each active material layer, From a viewpoint of suppressing electronic resistance, it is preferable that the thickness (one side) of each active material layer is about 1-120 micrometers.

  With respect to the porosity of each active material layer, the porosity of each active material layer is 10 from the viewpoint of increasing the conductivity (diffusibility) of Li ions by impregnating and holding the electrolytic solution and suppressing the electronic resistance. It is preferably about ˜40%.

(3) Electrolyte layer The electrolyte layer of this embodiment consists of an electrolyte and a separator formed by impregnating or holding the electrolyte in pores. The electrolyte layer having a separator functions as a spatial partition (spacer) between the positive electrode and the negative electrode. In addition, it also has a function of holding an electrolyte that is a lithium ion transfer medium between the positive and negative electrodes during charging and discharging. Further, in the present embodiment, as described above, the short circuit due to the thermal contraction of the separator can be prevented by bonding the separator and the electrode using the adhesive layer 18 (18a, 18b). Further, it is possible to prevent the adhesive portion (adhesive layer) on the separator side from being plastically deformed more than necessary at the adhesive interface between the electrode active material layer and the separator. In addition, the adhesion between the separator and the electrode can be maintained in the single battery layer (single cell) even when the electrode expands and contracts due to charge / discharge. As a result, clogging of the adhesive layer, which is the bonding part between the separator and the electrode, can be effectively suppressed / prevented, the cycle durability (capacity retention rate) of the battery can be improved, and the cycle is rapidly deteriorated. Can also be effectively prevented.

  There is no restriction | limiting in particular in the electrolyte which comprises an electrolyte layer, Polymer electrolytes, such as a liquid electrolyte and a polymer gel electrolyte and a polymer solid electrolyte, can be used suitably.

(3a) Liquid electrolyte The liquid electrolyte is obtained by dissolving a lithium salt as a supporting salt in a solvent. Examples of the solvent include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), ethyl methyl carbonate (EMC), methyl propionate (MP), methyl acetate (MA), and methyl formate (MF). 4-methyldioxolane (4MeDOL), dioxolane (DOL), 2-methyltetrahydrofuran (2MeTHF), tetrahydrofuran (THF), dimethoxyethane (DME), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC) , And γ-butyrolactone (GBL). These solvents may be used alone or as a mixture of two or more. As the supporting salt (lithium salt) is not particularly _{limited, LiPF 6, LiBF 4, LiClO} 4, LiAsF 6, LiTaF 6, LiSbF 6, LiAlCl 4, Li 2 B 10 Cl 10, LiI, LiBr, LiCl Inorganic acid anion salts such as LiAlCl, LiHF ₂ , LiSCN, LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, LiBOB (lithium bisoxide borate), LiBETI (lithium bis (perfluoroethylenesulfonylimide); And organic acid anion salts such as Li (C ₂ F ₅ SO ₂ ) ₂ N). These electrolyte salts may be used alone or in the form of a mixture of two or more.

  On the other hand, the polymer electrolyte is classified into a gel electrolyte containing an electrolytic solution and a polymer solid electrolyte containing no electrolytic solution.

(3b) Gel electrolyte The gel electrolyte has a configuration in which the above liquid electrolyte is injected into a matrix polymer having lithium ion conductivity. Examples of the matrix polymer having lithium ion conductivity include a polymer having polyethylene oxide in the main chain or side chain (PEO), a polymer having polypropylene oxide in the main chain or side chain (PPO), polyethylene glycol (PEG), poly Acrylonitrile (PAN), polymethacrylic acid ester, polyvinylidene fluoride (PVdF), copolymer of polyvinylidene fluoride and hexafluoropropylene (PVdF-HFP), polyacrylonitrile (PAN), poly (methyl acrylate) (PMA), poly (Methyl methacrylate) (PMMA) etc. are mentioned. In addition, mixtures of the above-described polymers, modified products, derivatives, random copolymers, alternating copolymers, graft copolymers, block copolymers, and the like can also be used. Among these, it is desirable to use PEO, PPO and their copolymers, PVdF, PVdF-HFP. In such a matrix polymer, an electrolyte salt such as a lithium salt can be well dissolved.

(3c) Polymer solid electrolyte The polymer solid electrolyte has a structure in which a supporting salt (lithium salt) is dissolved in the above matrix polymer, and does not contain an organic solvent. Therefore, when the electrolyte layer is composed of a polymer solid electrolyte, there is no fear of liquid leakage from the battery, and the battery reliability can be improved.

  A matrix polymer of a polymer gel electrolyte or a polymer solid electrolyte can exhibit excellent mechanical strength by forming a crosslinked structure. In order to form a crosslinked structure, thermal polymerization, ultraviolet polymerization, radiation polymerization, electron beam polymerization, etc. are performed on a polymerizable polymer (for example, PEO or PPO) for forming a polymer electrolyte, using an appropriate polymerization initiator. A polymerization treatment may be performed. In addition, the said electrolyte may be contained in the active material layer of an electrode.

  Further, in the present invention, it is desirable that the liquid electrolyte, the gel electrolyte and the like do not contain an additive for forming SEI. Thereby, the negative electrode active material surface in the vicinity of the negative electrode current collector inside the electrode and the negative electrode active material surface in the vicinity of the electrode (negative electrode active material layer) outside do not cause a problem that the thickness of the formed SEI is different. (For comparison, see FIGS. 7 to 10 and FIGS. 11 to 14). One purpose of the initial charging process is the formation of SEI. When the SEI formation additive is included in the liquid electrolyte, the gel electrolyte, etc., it is necessary to form the SEI by moving the additive in the liquid electrolyte on the positive electrode side or the gel electrolyte to the negative electrode side at the first charge. Since the process is followed, the first charge time is increased. Further, after that, as shown in FIG. 4, although it is necessary to perform high temperature aging over 14 days or more, and room temperature aging for 14 days or more, there is a problem that quality variation occurs as shown in FIG. there were. In this invention, since it is a battery structure obtained by the manufacturing method which adds the additive for SEI formation to a negative electrode slurry, and does not add to electrolyte solution and a positive electrode slurry, it is excellent at the point which can eliminate the above-mentioned subject.

(3d) Separator The separator is not particularly limited, and conventionally known separators can be appropriately used. For example, a porous sheet separator or nonwoven fabric separator made of a polymer or fiber that absorbs and holds the electrolyte can be used.

  As the separator of the porous sheet made of the polymer or fiber, for example, a microporous (microporous film) can be used. Specific examples of the porous sheet made of the polymer or fiber include polyolefins such as polyethylene (PE) and polypropylene (PP); a laminate in which a plurality of these are laminated (for example, three layers of PP / PE / PP) And a microporous (microporous membrane) separator made of a hydrocarbon resin such as polyimide, aramid, polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP), glass fiber, and the like.

  The thickness of the microporous (microporous membrane) separator cannot be uniquely defined because it varies depending on the intended use. For example, in applications such as secondary batteries for driving motors such as electric vehicles (EV), hybrid electric vehicles (HEV), and fuel cell vehicles (FCV), it is 4 to 60 μm in a single layer or multiple layers. Is desirable. The microporous (microporous membrane) separator preferably has a fine pore diameter of 1 μm or less (usually a pore diameter of about several tens of nanometers) and a porosity (porosity) of 20 to 80%. .

  As the nonwoven fabric separator, cotton, rayon, acetate, nylon, polyester; polyolefins such as PP and PE; conventionally known ones such as polyimide and aramid are used alone or in combination. The bulk density of the nonwoven fabric is not particularly limited as long as sufficient battery characteristics can be obtained by the impregnated polymer gel electrolyte.

  The nonwoven fabric separator preferably has a porosity (porosity) of 45 to 90%. Furthermore, the thickness of the nonwoven fabric separator may be the same as that of the electrolyte layer, preferably 5 to 200 μm, particularly preferably 10 to 100 μm. When the thickness is less than 5 μm, the electrolyte retention deteriorates, and when it exceeds 200 μm, the resistance increases.

(4) Adhesive layer The adhesive layer 18 (18a, 18b) is provided for the purpose of adhering to both the electrode (positive electrode or negative electrode) and the separator and preventing a short circuit due to thermal contraction of the separator. . In the present embodiment, it is necessary to form an adhesive layer so that the above-described appropriate adhesive strength and air permeability ratio can be provided. Thereby, it is possible to prevent the adhesive portion (adhesive layer) on the separator side from being plastically deformed more than necessary at the adhesive interface between the electrode active material layer and the separator. In addition, the adhesion between the separator and the electrode can be maintained in the single battery layer (single cell) even when the electrode expands and contracts due to charge / discharge. As a result, clogging of the adhesive layer, which is the bonding part between the separator and the electrode, can be effectively suppressed / prevented, the cycle durability (capacity retention rate) of the battery can be improved, and the cycle is rapidly deteriorated. Can also be effectively prevented.

  The material used for the adhesive layer is an insulating material that can achieve the above-described purpose, and may be any material that does not cause a side reaction (oxidation-reduction reaction) during charge and discharge, and is used for a binder for a lithium ion secondary battery. However, it is not particularly limited. For example, the following materials are mentioned. Olefin resins such as polyethylene (PE) and polypropylene (PP), polyethylene terephthalate (PET), polyether nitrile, polyacrylonitrile, polyimide, polyamide, cellulose, carboxymethyl cellulose (CMC), ethylene-vinyl acetate copolymer, polychlorinated Vinyl, styrene / butadiene rubber (SBR), isoprene rubber, butadiene rubber, ethylene / propylene rubber, ethylene / propylene / diene copolymer, styrene / butadiene / styrene block copolymer and hydrogenated products thereof, styrene / isoprene / styrene Thermoplastic polymers such as block copolymers and hydrogenated products thereof, polyvinylidene fluoride (PVdF), polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP), Lafluoroethylene (PTFE), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), ethylene / tetrafluoroethylene copolymer (ETFE), polychloro Fluoropolymers such as trifluoroethylene (PCTFE), ethylene / chlorotrifluoroethylene copolymer (ECTFE), polyvinyl fluoride (PVF), vinylidene fluoride-hexafluoropropylene-based fluororubber (VDF-HFP-based fluororubber), Vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene fluorine rubber (VDF-HFP-TFE fluorine rubber), vinylidene fluoride-pentafluoropropylene fluorine rubber (VDF) PFP-based fluororubber), vinylidene fluoride-pentafluoropropylene-tetrafluoroethylene-based fluororubber (VDF-PFP-TFE-based fluororubber), vinylidene fluoride-perfluoromethylvinylether-tetrafluoroethylene-based fluororubber (VDF-PFMVE) -TFE fluorine rubber), vinylidene fluoride-chlorotrifluoroethylene fluorine rubber (VDF-CTFE fluorine rubber) and other vinylidene fluoride fluorine rubber, epoxy resin, (meth) acrylic resin, aramid, etc. . Among these, polyvinylidene fluoride, polyimide, styrene / butadiene rubber, carboxymethyl cellulose, polypropylene, polytetrafluoroethylene, polyacrylonitrile, and polyamide are more preferable. The materials used for these suitable adhesive layers are excellent in heat resistance, have a very wide potential window, are stable at both the positive electrode potential and the negative electrode potential, and can be used for the adhesive layer. The materials used for these adhesive layers may be used alone or in combination of two or more. However, it goes without saying that the material used for the adhesive layer is not limited to these. Of these, for example, materials containing polyvinylidene fluoride (PVdF) or PVDF, (meth) acrylic resins, olefinic resins, etc. are resistant to both positive and negative electrode potentials. Applicable. SBR or the like is preferably used on the negative electrode side because it is strong against the negative electrode potential. Furthermore, PTFE is preferably used on the positive electrode side because it is resistant to the positive electrode potential. Here, the material containing PVDF or PVDF can set the bonding temperature (the temperature at which the surface of the bonding layer starts to soften and have adhesiveness; the softening start temperature) at a temperature lower than the separator deformation temperature range. Therefore, since the battery reaction is not inhibited as much as possible, there is a further effect on the output characteristics. Furthermore, PVDF and PVDF-containing materials have a large amount of modification from the softening start temperature, and can be bonded immediately, so that the hot press time can be shortened or the hot press temperature can be set low.

Moreover, as a material containing PVDF, a homopolymer of PVDF, a material in which a substituent (for example, a carboxyl group) is introduced into a part of PVDF (for example, a side chain of a repeating unit), PVDF and one or more other materials Random, block, alternating, graft copolymer (binary copolymer, ternary copolymer, quaternary copolymer, etc.) with polymer, PVDF and one or more other (co) polymers Examples thereof include polymer alloys. Among them, PVDF mixed with a carboxyl group (for example, a structure having a carboxyl group partially in the side chain; — (CH (COOH) —CF ₂ ) _n —, or — (CH ₂ —CF (COOH) ) _n -, or _{- (CH 2 -CF 2 -)} n - (CH (COOH) -CF 2) m -, or _{- (CH 2 -CF 2 -)} n - (CH 2 -CF (COOH)) m -Etc.) is desirable. By mixing a carboxyl group into PVDF, the melting point can be lowered (adjusted) by about 1 to 10 ° C. By adjusting the amount of carboxyl groups mixed in this way, the adhesive temperature (adhesion) of each adhesive layer of the battery stack is such that the end layer (upper and lower ends) and the center adhesive layer of the battery stack start to soften simultaneously. The surface of the layer begins to soften and the temperature at which it has adhesiveness; Similarly, since SBR is a copolymer of styrene and butadiene, the melting point can be increased by about 1 to 10 ° C. by increasing the proportion of styrene. By adjusting the ratio of styrene in this way, the adhesive temperature (of the adhesive layer) of each adhesive layer of the battery laminate is such that the adhesive layer on the end side (upper and lower ends) and the central side of the battery laminate starts to soften simultaneously. The temperature at which the surface starts to soften and has adhesiveness; the softening start temperature) can also be easily adjusted.

  The thickness of the adhesive layer should be as thin as possible within the range in which the above-mentioned objects and effects of the present embodiment can be achieved. This can suppress the increase in the diffusion distance of Li ions and contribute to the weight reduction of the battery. desirable. From this viewpoint, the thickness of the adhesive layer depends on the form of the adhesive layer, but when the adhesive layer is present on the entire surface of the separator and the electrode (entire surface), 0.1 to 10 μm is preferable, and more preferable. It is 0.1-5 micrometers, Most preferably, it is the range of 1-2 micrometers. If the thickness of the adhesive layer is 0.1 μm or more, it is preferable because the adhesion between the separator and the electrode can be sufficiently maintained and the production can be facilitated. If the thickness of the adhesive layer is 10 μm or less, it is preferable because the risk of adversely affecting the load characteristics of the battery is small and the energy density can be prevented from significantly decreasing.

  Moreover, when the adhesion part (adhesion layer) exists in stripe form or the dot form in the separator and the whole electrode surface (refer FIG. 3), the thickness of an adhesion layer is 0.1-5 micrometers, Preferably it is 1 It is in the range of ˜2 μm. If the thickness of the adhesive layer is 0.1 μm or more, it is preferable because it can be easily manufactured, and if the thickness of the adhesive layer is 5 μm or less, it is preferable because there is little possibility of adversely affecting the load characteristics of the battery.

  The thickness of the adhesive layer can be measured from a cross-sectional image of an SEM (scanning electron microscope) by disassembling the battery and taking out a cross-section because the adhesive layer is brittle and may not peel off well.

  The porosity of the adhesive layer (also referred to as porosity) depends on the separator porosity and the form of the adhesive layer, but when the adhesive layer is present on the entire surface of the separator and electrode (entire surface), stripes or dots When the adhesive part exists in the shape, it is 30 to 90%, preferably 60 to 90%. If the porosity of the adhesive layer is 30% or more, it is excellent in that it can prevent clogging and prevent increase in resistance without impeding the diffusion of Li ions. When the porosity of the adhesive layer is 90% or less, it is possible to effectively suppress the adhesive force from being significantly reduced. The porosity of the adhesive layer listed above is an example of a combination that is suitable when the separator porosity is about 45 to 55%. When the porosity of the separator increases or decreases, the adhesive layer The porosity may be increased or decreased in proportion to this. The reason why the porosity of the adhesive layer is slightly higher than the separator porosity is to prevent the diffusion of Li ions from being inhibited by the presence of the adhesive layer formed on the electrode surface. .

  On the other hand, when the adhesive portion is provided in a dot shape and the proportion of the adhesive portion is very small, the porosity of the adhesive portion (adhesive layer) should be rather small, preferably 10% or less, preferably 0. %. This is because the non-adhesive portion having a large ratio functions effectively as a new electrolyte solution holding portion. What is necessary is just to determine suitably the ratio of the adhesion part when the ratio of an adhesion part is very small in consideration of adhesiveness and battery performance. However, as described above, there is no particular problem even if the porosity of the adhesive portion (adhesive layer) is 60% or more, preferably 60 to 90%.

  The porosity present in the adhesive layer can be measured using the mercury intrusion method or the like after disassembling the battery, taking out each adhesive layer, washing and removing the electrolyte, and drying. However, if the adhesive layer is brittle and cannot be peeled off, disassemble the battery, take out the cross section, and count (measure) the space portion of the adhesive layer from the cross-sectional image of the SEM (scanning electron microscope) by mapping. You can also.

  Moreover, the ratio of the adhesion part (or non-adhesion part) which exists in the separator and the electrode surface disassembles a battery, takes out a cross section, and counts (measures) the adhesion part (dot) by mapping from the cross-sectional image of SEM. It can be calculated by

  The form of the adhesive layer is not particularly limited as long as it can achieve the objects and effects of the present embodiment. For example, (i) the adhesive layer may be present on the entire surface (entire surface) of the separator and the electrode. In this case, the bonding portion needs to be a porous layer so as to have a liquid retaining space (see the porosity). Alternatively, (ii) the adhesive layer may be present on the separator and the electrode surface at an interval so that an adhesive portion where the adhesive layer exists and a non-adhesive portion where the adhesive layer does not exist are formed. It is desirable that the bonding portion is arranged so that uniformity is maintained on the separator and the electrode surface. In the case of (ii) above, since the non-adhesive portion functions effectively as the liquid retention space, the adhesion portion (adhesive layer) may be a porous layer having a liquid retention space. Alternatively, it may be nonporous (= porosity (porosity) 0%) in which no liquid retention space exists. In particular, when an adhesive part is provided in a dot shape (= when the ratio of the adhesive part is very small), the adhesive part is made nonporous (= porosity (porosity) 0%) with no liquid retention space. It is good.

  FIG. 2A is a plan view showing a state in which stripe-shaped adhesive portions are provided on the electrode surface. 2B and 2C are plan views showing a state in which a dot-shaped adhesive portion is provided on the electrode surface.

  Specifically, (iii) As shown in FIG. 2A, a non-adhesive portion 35 is formed on the separator and electrode surface 31 between the stripe-shaped adhesive portion 33a and the stripe (33a) stripe (33a). The adhesive layer (33a) may be present at an interval. (Iib) As shown in FIGS. 2B and 2C, an adhesive layer is formed on the separator and electrode surface 31 such that a non-adhesive portion 35 is formed between the dot-like adhesive portion 33b and the dot (33b) and the dot (33b). (33b) may be present at intervals. As an example of (iib), (b1) The dot-like adhesion portions 33b exist only at the four corners of the separator and the electrode surface 31, and the non-adhesion portions 35 are formed on the separator and the electrode surface 31 other than the four corner dots (adhesion portion 33b). An adhesive layer may be present at an interval so that is formed (FIG. 2B). Alternatively, (b2) dot-like adhesive portions 33b are scattered on the separator and electrode surface 31 so as to maintain uniformity, and non-adhesive portions 35 are provided on the separator and electrode surface 31 between the dots (33b) and dots (33b). Adhesive layers may be present at intervals so as to be formed. For example, on the separator and electrode surface 31, a total of 12 dot-like adhesive portions 33 b with 3 horizontal points × 4 vertical points are scattered at equal intervals, and the separator and electrode surfaces other than 12 dots (adhesive portion 33 b) Adhesive layers may be present at intervals such that a non-adhesive portion 35 is formed on 31 (FIG. 2C). However, it is not limited to these forms at all, such as a lattice shape, a rhombus lattice shape, a strip shape, a ring shape such as a continuous or discontinuous circle or ellipse, a polygonal shape, a wave shape, a semicircular shape, an indefinite shape, etc. Any other form may be used as long as the object and effect of the present embodiment can be achieved.

  In the present embodiment, the softening point of the adhesive layer is preferably lower than the softening point of the separator. This is because it is excellent in that the electrode-separator can be adhered by softening the surface of the adhesive layer to bring out adhesion while maintaining the shape of the separator. From this viewpoint, it is preferable that the softening point of the adhesive layer is 5 to 10 ° C. lower than the softening point of the separator.

Here, the softening point temperature of the adhesive layer and the softening point temperature of the separator are both set to the Vicat softening temperature (Vicat Softening Temperature, VST), and can be measured by JIS K 7206 (1999). To explain the outline of JIS K 7206 (1999), a test piece having a prescribed size was set in a heating bath, and an end surface of a constant cross-sectional area (1 mm ^{2 in} JIS K 7206) was pressed to the center. Increase the temperature of the bathtub in the state. The temperature when the end surface bites into the test piece to a certain depth is the Vicat softening temperature (unit: ° C.).

  As shown in the examples, the adhesive layer is formed in advance by an adhesive slurry in which a resin material for forming the adhesive layer is dissolved in an appropriate solvent on the separator surface (the porosity of the adhesive layer can be adjusted by changing the concentration). Is applied to a desired thickness and shape (entire surface, stripe shape, dot shape, etc.) and dried. Thereby, a separator and an adhesive layer can be integrated. In addition, when providing an adhesive layer in any one of positive and negative electrodes, the effect of this embodiment is the same in any case. However, when the electrode sizes are different, the separator of the same size as the larger electrode is heat-shrinked and smaller than the smaller electrode when the electrode is provided on the larger electrode side (usually the negative electrode side). Up to this point, it can be said that the opposing electrodes do not contact each other, which is advantageous. A separator integrated with the adhesive layer is sandwiched between a positive electrode and a negative electrode in the same manner as a normal separator to form a power generation element (battery stack) 21. Thereafter, the surface of the adhesive layer 18 (adhesive portion) of the separator integrated with the adhesive layer is softened and bonded by hot pressing from the vertical direction of the power generating element 21 with a hot press device (see FIGS. 2 and 5) 20. Adhesive with the electrode. Thereby, the contact bonding layer 18 formed by bonding between the electrode and the separator can be formed. Furthermore, you may contact | connect a separator and an electrode through an adhesive layer by vacuum-sealing the electric power generation element 21 formed using the separator integrated with the adhesive layer, without hot-pressing. Thereby, the adhesive layer 18 formed by adhering between the electrode and the separator can also be formed. Or you may produce the electrode which apply | coated the adhesive slurry beforehand to the electrode (positive electrode or negative electrode) side, and was integrated with the contact bonding layer. Thereafter, the power generation element 21 is formed in the same manner, and the adhesive layer 18 formed by adhering between the electrode and the separator can be formed by hot pressing. Furthermore, the separator and the electrode may be brought into contact with each other through the adhesive layer by vacuum-sealing the power generating element 21 formed using the electrode integrated with the adhesive layer without performing hot pressing. Thereby, the adhesive layer 18 formed by adhering between the electrode and the separator can also be formed.

(5) Current collector (current collector tab; external lead)
In the lithium ion secondary battery (laminated structure battery) 10, current collecting plates (current collecting tabs) 25 and 27 may be used for the purpose of taking out current outside the battery. The current collector plates (current collector tabs) 25 and 26 are electrically connected to the current collectors 11 and 12 and are taken out to the outside such as a laminate film as an exterior material.

  The material constituting the current collecting plates 25 and 27 is not particularly limited, and a known highly conductive material conventionally used as a current collecting plate for a lithium ion secondary battery can be used. As a constituent material of the current collector plate, for example, metal materials such as aluminum, copper, titanium, nickel, stainless steel (SUS), and alloys thereof are preferable. From the viewpoint of light weight, corrosion resistance, and high conductivity, aluminum and copper are more preferable, and aluminum is particularly preferable. In addition, the same material may be used for the positive electrode current collecting plate (positive electrode current collecting tab) 25 and the negative electrode current collecting plate (negative electrode current collecting tab) 27, and different materials may be used.

(5a) Electrode (positive electrode and negative electrode) terminal lead (internal lead)
In the laminated battery 10 shown in FIG. 1, the current collectors 11 and 12 are electrically connected to current collector plates (current collecting tabs) 25 and 27 through a negative terminal lead and a positive terminal lead (not shown), respectively. It may be connected. However. A part of the current collectors 11 and 12 can be extended like electrode terminal leads (internal leads) and directly connected to current collector plates (current collection tabs) 25 and 27. Therefore, the electrode terminal lead (not shown) can be said to be an optional component that may be used as needed.

  As a material for the negative electrode and the positive electrode terminal lead, a lead used in a known laminated secondary battery can be used. In addition, the parts removed from the battery exterior material should be heat-insulating so that they do not affect products (for example, automobile parts, especially electronic devices) by touching peripheral devices or wiring and causing leakage. It is preferable to coat with a heat shrinkable tube or the like.

(6) Battery exterior material As a battery exterior material, a conventionally well-known metal can case can be used. In addition, the power generation element 21 may be packed using a laminate film 29 as shown in FIG. The laminate film can be configured as a three-layer structure in which, for example, polypropylene, aluminum, and nylon are laminated in this order. By using such a laminate film, it is possible to easily open the exterior material, add the capacity recovery material, and reseal the exterior material. In addition, a laminate film exterior material is also desirable from the viewpoint that it is excellent in high output and cooling performance and can be suitably used for a battery for large equipment for EV and HEV.

[Appearance structure of lithium ion secondary battery]
FIG. 3 is a perspective view showing the appearance of a flat laminated (laminated structure) lithium ion secondary battery which is a typical embodiment of a laminated battery.

  As shown in FIG. 3, the flat laminated lithium ion secondary battery 30 has a rectangular flat shape, and a positive current collecting tab 38 for taking out electric power from both sides thereof, a negative current collecting tab, and the like. The electric tab 39 is pulled out. The power generation element 37 is wrapped by the battery outer packaging material 32 of the lithium ion secondary battery 30 and the periphery thereof is heat-sealed. The power generation element 37 pulls out the positive electrode current collection tab 38 and the negative electrode current collection tab 39 to the outside. Sealed. Here, the power generation element 37 corresponds to the power generation element 21 of the stacked lithium ion secondary battery (stacked structure battery) 10 shown in FIG. 1 described above. The power generation element 37 is formed by laminating a plurality of single battery layers (single cells) 19 composed of a positive electrode, an electrolyte layer, and a negative electrode.

  The lithium ion secondary battery is not limited to a stacked flat shape. The wound lithium ion secondary battery may have a cylindrical shape, or may have a shape that is a flattened rectangular shape by deforming such a cylindrical shape. There is no particular limitation. In the said cylindrical shape thing, a laminate film may be used for the exterior material, and the conventional cylindrical can (metal can) may be used, for example, It does not restrict | limit. Preferably, the power generation element is covered with an aluminum laminate film. With this configuration, weight reduction can be achieved.

  Further, the removal of the current collecting tabs 38 and 39 shown in FIG. 3 is not particularly limited. The positive electrode current collecting tab 38 and the negative electrode current collecting tab 39 may be drawn out from the same side, or the positive electrode current collecting tab 38 and the negative electrode current collecting tab 39 may be divided into a plurality of parts and taken out from each side. It is not limited to the one shown in FIG. Further, in a wound type lithium ion battery, instead of a tab, for example, a terminal may be formed using a cylindrical can (metal can).

  The lithium ion secondary battery (stacked structure battery) 10 is a vehicle drive that requires a high volume energy density and a high volume output density as a large-capacity power source for an electric vehicle, a hybrid electric vehicle, a fuel cell vehicle, and a hybrid fuel cell vehicle. It can be suitably used as a power source or auxiliary power source.

  In addition, although the said embodiment illustrated the laminated type lithium ion secondary battery as a laminated structure battery, it is not necessarily restricted to this, For another type of secondary battery, Furthermore, to a primary battery and a capacitor. Is also applicable.

  The nonaqueous electrolyte secondary battery (laminated structure battery) of the present embodiment described above has the following effects.

  Since the nonaqueous electrolyte secondary battery (laminated structure battery) 10 of this embodiment has a negative electrode formed using a negative electrode slurry containing an additive for SEI formation, SEI is uniformly formed in the negative electrode. Since SEI becomes a resistance component, the nonaqueous electrolyte secondary battery (laminated structure battery) of the present invention that is uniformly formed is excellent in that the capacity reduction is suppressed and the life can be extended (FIGS. 11 to 11). 14 and FIG. 7 to FIG. 10).

[Method for producing non-aqueous electrolyte secondary battery]
The method for producing a non-aqueous electrolyte secondary battery of the present invention is characterized in that the negative electrode slurry used for forming the negative electrode contains an additive for SEI formation. Preferably, it is desirable that neither the electrolyte solution nor the positive electrode slurry used for positive electrode formation contains an additive for SEI formation.

  FIG. 4 is a drawing showing the process flow of the manufacturing method of the present invention. As shown in FIG. 4, the production method of the present invention includes a positive electrode forming step [I] using a positive electrode slurry, a negative electrode forming step [II] using a negative electrode slurry, and a positive electrode and a negative electrode obtained in the forming step. And a step [III] of laminating a separator to form a laminate, and a step [IV] of injecting an electrolyte into the laminate. The negative electrode slurry contains an additive for forming SEI. Preferably, neither the electrolyte solution nor the positive electrode slurry contains an additive for forming SEI. With the manufacturing method of the present invention having such a configuration and the battery obtained thereby, the operational effects of the above-described invention can be achieved. Hereinafter, each step shown in FIG. 4 will be described.

[I] Positive Electrode Formation Step The positive electrode formation step [I] using the positive electrode slurry is not particularly limited, and a conventionally known method can be applied. Hereinafter, the positive electrode forming step [I] will be described.

  The positive electrode forming step [I] is not particularly limited, and may be performed by the following steps (1) to (3) from the viewpoint of mass production (production efficiency). The process procedure is not limited at all. First, (1) a positive electrode slurry is prepared (positive electrode slurry preparation step). (2) Next, apply the positive electrode slurry to the surface of the current collector, dry, and roll press the resulting positive electrode slurry to produce a positive electrode raw material (positive electrode raw material preparation step). (3) The positive electrode raw material obtained above is cut into a desired shape and size using a cutting means, and dried to obtain a positive electrode (positive electrode manufacturing step).

(1) Positive electrode slurry preparation step (“slurry production” step 1a in FIG. 4)
(Method for preparing positive electrode slurry)
This step is not particularly limited as long as a positive electrode slurry can be prepared, and conventionally known methods can be applied. Specifically, the slurry is prepared by adding a slurry viscosity adjusting solvent (NMP or the like) in which a binder is dissolved in a positive electrode active material and a conductive additive, and further adding and mixing the solvent to adjust the viscosity. That is, the positive electrode slurry is slurried (inked) from the slurry viscosity adjusting solvent and the solid content using a homogenizer or a kneader.

(Composition of positive electrode slurry)
The positive electrode slurry thus obtained is a solution containing a positive electrode active material. As other components, a conductive additive, a binder, a polymerization initiator, an electrolyte raw material (polymer or host polymer for solid electrolyte, electrolyte, etc.), a supporting salt (lithium salt), a slurry viscosity adjusting solvent, and the like are optionally included. That is, the positive electrode slurry optionally includes, in addition to the positive electrode active material, a conductive additive, an electrolyte raw material, a supporting salt (lithium salt), a slurry viscosity adjusting solvent, a polymerization initiator, and the like, in the same manner as a solution-type lithium ion battery. It can be produced by mixing the materials at a predetermined ratio.

  Furthermore, in the present invention, it is desirable that the positive electrode slurry does not contain an additive for forming SEI. As a result, in the same manner as when the SEI forming additive is added to the conventional electrolyte, it is formed on the surface of the negative electrode active material near the current collector inside the electrode and the surface of the negative electrode active material near the outside of the electrode (active material layer). This can greatly contribute to solving the problem that the thickness of SEI differs. One purpose of the initial charging process is the formation of SEI. When there is an SEI formation additive on the positive electrode side, the same process as when adding an SEI formation additive to a conventional electrolyte solution follows a complicated process. It can greatly contribute to eliminating the problem.

  When a polymer gel electrolyte is used for the electrolyte layer, the positive electrode slurry includes, in addition to the positive electrode active material, a conventionally known binder that binds the positive electrode active material fine particles to each other, a conductive auxiliary agent for increasing electronic conductivity, and a solvent. Etc. should be included. Therefore, the host polymer, electrolyte solution, lithium salt, and the like, which are raw materials for the polymer gel electrolyte, may not be included. The same applies when a separator having an electrolyte layer impregnated with an electrolyte is used.

(Solid content contained in positive electrode slurry (component of positive electrode active material layer))
Here, the solid content (components of the positive electrode active material layer) in the positive electrode slurry such as the positive electrode active material, the conductive additive and the binder is as described above. What is necessary is just to mix | blend the quantity of each component of these solid content, respectively so that it may become the structure ratio (content of each component) of a positive electrode active material layer.

  Examples of the polymer material of the electrolyte contained in the positive electrode slurry (host polymer of polymer gel electrolyte or polymer material of polymer solid electrolyte) include PEO, PPO, and copolymers thereof, and is crosslinked within the molecule. It is preferable to have a functional group (such as a carbon-carbon double bond). By cross-linking the polymer electrolyte using this cross-linkable functional group, the mechanical strength is improved.

  The polymerization initiator needs to be selected according to the compound to be polymerized. For example, benzyl dimethyl ketal is used as the photopolymerization initiator, and azobisisobutyronitrile is used as the thermal polymerization initiator. The addition amount of the polymerization initiator is determined according to the number of crosslinkable functional groups contained in the polymer material of the electrolyte. Usually, it is about 0.01-1 mass% with respect to a polymeric raw material.

(Slurry viscosity adjusting solvent contained in positive electrode slurry)
The slurry viscosity adjusting solvent is not particularly limited, and examples thereof include N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, and methylformamide.

(Viscosity of positive electrode slurry)
It is not necessary to be particularly concerned about the viscosity of the positive electrode slurry, and can be applied in a wide viscosity range. Here, the viscosity of the positive electrode slurry is preferably 500 to 10000 mPa · s, more preferably 800 to 9000 mPa · s, and still more preferably 1000 to 8000 mPa · s. When the viscosity of the positive electrode slurry is 500 mPa · s or more, the positive electrode slurry can be uniformly applied to a predetermined thickness on the current collector foil to be conveyed using a coating machine (coater or the like). In the positive electrode obtained as a result, a positive electrode active material layer having a uniform and flat surface can be formed. If the viscosity of the positive electrode slurry is 100000 mPa · s or less, the positive electrode slurry can be uniformly applied to a predetermined thickness on the current collector foil conveyed using a coating machine (coater, etc.), and then Can be dried in a short time. In the positive electrode obtained as a result, a positive electrode active material layer having a uniform and flat surface can be formed.

(2) Positive electrode fabric preparation process (“application / drying” process 1b + “press” process 1c in FIG. 4)
This step is not particularly limited as long as the obtained positive electrode slurry can be applied to the surface of the current collector, dried and pressed to produce the positive electrode raw material, and a conventionally known method is applied. Can do.

(Current collector; positive electrode current collector foil)
The current collector is as described above. In addition, when using it for preparation of a positive electrode raw material, similarly to a conventionally well-known manufacturing method, the metal thin film (The metal foil which consists of the material used for a collector and thickness, for example, 20-micrometer-thick aluminum foil). It is desirable to purchase it as a roll and use it as a positive electrode current collector foil.

(Slurry application)
The method of applying the positive electrode slurry to the surface of the current collector that is continuously conveyed while being unwound from the positive electrode current collector foil attached to the unwinding roller is not particularly limited, and a conventionally known method is applied. Can do. For example, a coating method using a coater, a patterning coating method such as an ink jet method or a screen printing coating method can be used as a method capable of continuously coating the positive electrode slurry on the continuously conveyed current collector. In the slurry application, it is desirable that the coating is generally performed so that the basis weight or the accuracy of the application mass is within a range of about ± 5% by mass (any part).

(Conveying means)
As the current collector foil conveying means, a conventionally known conveying means can be used. For example, it is possible to use a guide roll or the like provided at regular intervals so that the current collector foil traveling between the winding roll and the winding roll can be stably conveyed. Absent. With respect to the guide roll, the current collector foil and further the positive electrode slurry applied on the current collector foil are passed through a coating machine (coater), a drying device (drying furnace), and further a roll press device and conveyed. It is provided for. For this reason, an appropriate number is appropriately arranged at the locations necessary for passing and transporting around and inside the various devices described above. In other words, other than the guide rolls, various well-known conveying means are appropriately used, not shown. By using such a conveying means, the manufacturing speed can be increased while suppressing the equipment cost, and the positive electrode active material layer can be manufactured while reducing the cost.

(Drying; Removal of slurry viscosity adjusting solvent)
Next, the current collector on which the positive electrode slurry coating film is formed is dried, and the slurry viscosity adjusting solvent contained in the slurry coating film is removed. The drying conditions are not particularly limited, and conventionally known production methods can be applied. Specifically, the drying conditions are determined according to the applied positive electrode slurry and cannot be uniquely defined, but are usually 40 to 150 ° C., preferably 80 to 130 ° C., and 5 minutes to 20 hours. The drying atmosphere is not particularly limited, and is preferably performed in an air atmosphere from the viewpoint of production cost, but is not limited thereto. As the drying means (apparatus), a drying means using hot air drying and infrared (IR) drying capable of normal continuous drying can be used, and a drying means using vacuum drying can also be used. Moreover, you may use the drying means which used hot air drying and IR drying together.

  The above application and drying are performed on the current collector surface (A surface), and then the other surface (B surface) of the current collector is applied and dried in the same manner on both surfaces of the current collector. A dry coating film can be formed. In addition, you may perform the said application | coating and drying simultaneously for both A surface and B surface. In the case where the application and drying are performed simultaneously on both the A side and the B side, from the viewpoint of preventing the slurry on the lower side from dripping, the current carrying direction of the current collector is changed from the horizontal direction to the vertical direction (from top to bottom). Alternatively, the method may be performed from the bottom to the top). In this case, a conveying device, a coating (coating) device, a drying device, and the like may be installed from horizontal to vertical (or from vertical to horizontal). In the case of a bipolar electrode, a dry coating film (positive electrode active material layer) is formed on the A surface (or B surface) using the positive electrode slurry, and a negative electrode slurry described later is formed on the B surface (or A surface). It may be used to form a dry coating film (negative electrode active material layer). Also in this case, the application and drying may be performed in the order of the A surface and the B surface, or the application and drying may be performed simultaneously on both the A surface and the B surface.

(Dry coating press)
Next, by pressing the current collector having the dried coating film after drying the slurry coating film and adjusting the slurry dried coating film (positive electrode active material layer) to have a target density, obtain.

The press conditions are not particularly limited, and conventionally known production methods can be applied. Specifically, the slurry dry coating film (positive electrode active material layer) falls within the target density range of 0.90 to 1.10 g / cm ³ by roll pressing while continuously transporting the current collector having the dry coating film on both sides. It is desirable to adjust as follows. However, the present invention is not limited to the above target density range, and may be appropriately determined in consideration of the purpose of use of the battery (output importance, energy importance, etc.), ion conductivity, and the like. The press method may be either a cold press or a hot press.

  In addition, the collector which has a dry coating film can be normally obtained as a roll-form positive electrode raw material by roll-rolling, carrying continuously, and winding on a winding roller. Preferably, the positive electrode fabric (current collector having a dried coating film) to be conveyed after the pressing may be cut by the following cutting means without being wound by a winding roller.

(3) Positive electrode manufacturing step (“slit” step 1d in FIG. 4)
In this step, the positive electrode fabric obtained above is cut (cut) into a desired shape and size using a cutting means, and dried to obtain a positive electrode.

(Cut positive electrode fabric (cutting))
The method for cutting the positive electrode raw material obtained above into a desired shape and size using an appropriate cutting means is not particularly limited, and a conventionally known production method can be applied. Specifically, the positive electrode raw material wound up in a roll shape by the take-up roller obtained above is attached again to the unwinding roller, and the positive electrode raw material is not unwound, so a cutting means such as a slitter is used. Then, it may be cut into a rectangular shape in accordance with the desired shape and size, specifically, the target electrode size. The cutting means is not limited to the slitter and the like, and conventionally known cutting means can be used as appropriate. Preferably, the positive electrode fabric (current collector having a dried coating film) conveyed after the pressing step without being wound by a take-up roller is made to have a desired electrode size using a cutting means such as a slitter. In addition, it is desirable to cut it into a rectangular shape or the like in terms of reducing the man-hours.

(Drying; removal of adhering water)
Next, the cut positive electrode is dried to remove moisture adhering to the drying in the positive electrode raw material preparation step (2). The drying conditions are not particularly limited, and conventionally known production methods can be applied. Specifically, the drying conditions are determined according to the size of the positive electrode and cannot be uniquely defined. Usually, however, drying is performed at 70 ° C. or higher for 7 hours or longer using a vacuum dryer. The drying atmosphere is not particularly limited, but it is desirable to perform vacuum drying under reduced pressure after substitution with an inert gas (nitrogen gas), but is not limited thereto. As the drying means (apparatus), a drying means using a vacuum drying apparatus can also be used. Moreover, you may use the drying means which used vacuum drying and IR drying together. Through the drying, a positive electrode having a desired target density, size, and shape can be obtained.

[II] Negative electrode forming step The present invention is characterized in that the negative electrode slurry used for forming the negative electrode contains an additive for SEI formation. The negative electrode forming step [II] using the negative electrode slurry is not particularly limited, and a conventionally known method can be applied. Hereinafter, the negative electrode forming step [II] will be described.

  The negative electrode formation step [II] is not particularly limited, and may be carried out by the following step procedures (1) to (3) from the viewpoint of mass production (production efficiency), but is not necessarily performed. There is no limit to this. First, (1) a negative electrode slurry is prepared (negative electrode slurry preparation step). (2) Next, the obtained negative electrode slurry is coated with the negative electrode slurry on the surface of the current collector, dried and pressed to produce a negative electrode original fabric (negative electrode original fabric production step). (3) The negative electrode raw material obtained above is cut into a desired shape and size using a cutting means, and dried to obtain a negative electrode (negative electrode preparation step).

(1) Negative electrode slurry preparation step (“slurry preparation” step 2a in FIG. 4)
(Method for preparing negative electrode slurry)
As long as this process can prepare the negative electrode slurry containing the additive for SEI formation which is the characteristic of this invention as mentioned above, a conventionally well-known preparation method can be applied suitably. Specifically, the negative electrode active material, the conductive additive, and the SEI forming additive are mixed while adding a slurry viscosity adjusting solvent (NMP or the like) in which a binder is dissolved, and the solvent is further added and mixed to adjust the viscosity. FIG. 5A is a drawing schematically showing an outline of a slurry preparation apparatus. FIG. 5B is a drawing schematically showing a method for preparing a negative electrode slurry using the slurry preparing apparatus of FIG. 5, and FIG. 5C schematically shows a state of the negative electrode active material in the slurry obtained from FIG. 5B. It is the drawing. As shown in FIGS. 5A and 5B, a slurry viscosity in which a positive electrode active material (powder), a conductive auxiliary agent (powder), and an additive for SEI formation (powder) are placed in a container 52 of a slurry preparation apparatus 51 and a binder is dissolved. It is prepared by mixing (dispersing / stirring) using the stirring means 54 provided in the container lid 53 while adding the adjusting solvent (NMP or the like), further adding the solvent, mixing and adjusting the viscosity. As the positive electrode slurry, a negative electrode slurry may be prepared from the slurry viscosity adjusting solvent and the solid content using a homogenizer or a kneading apparatus in addition to the slurry preparation apparatus 51 shown in FIG. In the obtained negative electrode slurry, as shown in FIG. 5C, the SEI forming additive 56 dissolved or dispersed in the slurry viscosity adjusting solvent (NMP or the like) is coated or adhered on the surface of the negative electrode active material (particles) 55. The SEI forming additive is coated or adhered to the surface of the negative electrode active material (particles) 55 in a dissolved or dispersed state by subsequent drying (see FIGS. 11A and 12).

(Composition of negative electrode slurry)
The negative electrode slurry thus obtained is a solution containing at least a positive electrode active material and an additive for SEI formation. As other components, a conductive additive, a binder, a polymerization initiator, an electrolyte raw material (polymer or host polymer for solid electrolyte, electrolyte, etc.), a supporting salt (lithium salt), a slurry viscosity adjusting solvent, and the like are optionally included. That is, the negative electrode slurry is the same as the solution type lithium ion battery except that it contains the SEI forming additive, which is a feature of the present invention, in addition to the negative electrode active material, the conductive additive, the electrolyte raw material, the supporting salt (lithium Salt), a slurry viscosity adjusting solvent, a polymerization initiator, and the like.

  In the case where a polymer gel electrolyte is used for the electrolyte layer, the negative electrode slurry includes a conventionally known binder that binds the negative electrode active material fine particles in addition to the negative electrode active material and the SEI forming additive, in order to increase electronic conductivity. The conductive auxiliary agent, the solvent and the like may be included. Therefore, the host polymer, electrolyte solution, lithium salt, and the like, which are raw materials for the polymer gel electrolyte, may not be included. The same applies when a separator having an electrolyte layer impregnated with an electrolyte is used.

(Solid content in negative electrode slurry (component of positive electrode active material layer))
Here, the solid content (components of the negative electrode active material layer) in the negative electrode slurry such as the negative electrode active material, the conductive additive, and the binder is as described above. What is necessary is just to mix | blend the quantity of each component of these solid content, respectively so that it may become the structure ratio (content of each component) of a negative electrode active material layer.

  Examples of the polymer material of the electrolyte contained in the negative electrode slurry (host polymer of polymer gel electrolyte or polymer material of solid polymer electrolyte) include PEO, PPO, and copolymers thereof, and is crosslinked within the molecule. It is preferable to have a functional group (such as a carbon-carbon double bond). By cross-linking the polymer electrolyte using this cross-linkable functional group, the mechanical strength is improved.

  The polymerization initiator needs to be selected according to the compound to be polymerized. For example, benzyl dimethyl ketal is used as the photopolymerization initiator, and azobisisobutyronitrile is used as the thermal polymerization initiator. The addition amount of the polymerization initiator is determined according to the number of crosslinkable functional groups contained in the polymer material of the electrolyte. Usually, it is about 0.01-1 mass% with respect to a polymeric raw material.

(Additive for SEI formation contained in negative electrode slurry)
The production method of the present invention is characterized in that the negative electrode slurry used for forming the negative electrode contains an additive for forming SEI. Thereby, the negative electrode active material surface in the vicinity of the negative electrode current collector inside the electrode and the negative electrode active material surface in the vicinity of the electrode (negative electrode active material layer) outside do not cause a problem that the thickness of the formed SEI is different. (For comparison, see FIGS. 7 to 10 and FIGS. 11 to 14). One purpose of the initial charging process is the formation of SEI. If there is an additive for SEI formation in the electrolytic solution, it is necessary to move the additive in the electrolytic solution on the positive electrode side to the negative electrode side to form SEI at the time of initial charging. The time will be longer. Further, after that, as shown in FIG. 4, although it is necessary to perform high temperature aging over 14 days or more, and room temperature aging for 14 days or more, there is a problem that quality variation occurs as shown in FIG. there were. In the manufacturing method of this invention, it is excellent at the point which can eliminate the above-mentioned subject by setting it as the structure which adds the additive for SEI formation to a negative electrode slurry, and does not add to electrolyte solution and a positive electrode slurry.

  The SEI-forming additive preferably contains a compound that is reductively decomposed at a noble potential higher than 0.2 V with respect to lithium metal. Specifically, it is desirable that the SEI forming additive includes at least one selected from the group consisting of vinylene carbonate, sulfonic acid ester, and derivatives thereof. The additive for SEI formation functions to suppress reaction with the electrolyte by being reduced and decomposed before the electrolyte is decomposed to form a dense and stable film (SEI) on the active material surface. . When the lithium ion begins to be intercalated to the negative electrode active material (particles) such as graphite, the reactivity of the negative electrode increases rapidly. Also, when lithium ions solvated with solvent molecules in the electrolyte are intercalated into negative electrode active materials (particles) such as graphite, they are desolvated but the film (SEI) quality is poor In some cases, the desolvation reaction is not carried out smoothly, leading to a decrease in battery characteristics, or deterioration such as peeling of the surface layer of a negative electrode active material (particle) such as graphite. Therefore, as an additive for SEI formation, it has a potential no higher than 0.2 V at which lithium ion intercalation with respect to the negative electrode active material (particles) starts, such as at least a reductive decomposition potential, and is dense and electrochemical. It is desirable to form a highly stable coating (SEI).

  Here, the sulfonic acid ester and derivatives thereof are not particularly limited, and examples thereof include intramolecular cyclic esters such as chain monoesters, chain diesters, cyclic diesters, and sultone and derivatives thereof. Examples of the sulfonic acid ester include a chain sulfonic acid ester, a cyclic monosulfonic acid ester, and a cyclic disulfonic acid ester, but are not limited thereto.

  Examples of the chain sulfonic acid ester include methanesulfonic acid methyl ester, methanesulfonic acid ethyl ester, and busulfan (tetramethylene-bis (methanesulfonate)), but are not limited thereto.

  Examples of the cyclic monosulfonic acid ester include 1,3-propane sultone, 1,4-butane sultone, α-trifluoromethyl-γ-sultone, β-trifluoromethyl-γ-sultone, which are cyclic intramolecular esters, γ-trifluoromethyl-γ-sultone, α-methyl-γ-sultone, α, β-di (trifluoromethyl) -γ-sultone, α, α-di (trifluoromethyl) -γ-sultone, α- Examples include, but are not limited to, undecafluoropentyl-γ-sultone, α-heptafluoropropyl-γ-sultone, and the like.

  Examples of the cyclic disulfonate include, but are not limited to, methylene methane disulfonate, ethylene methane disulfonate, propylene methane disulfonate, and the like.

  Furthermore, as said sulfonate ester, what has at least any one of following Chemical formula 1, 2 is desirable.

  In the above formula, X represents an alkylene group which may have a side chain, or an oxygen atom. Y represents an alkylene group which may have a side chain, or an unsubstituted alkylene group. Z represents a methylene group or a single bond.

In the above formula, n is 0, 1, or 2, and R _{1 to} R ₆ are a hydrogen atom or an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, carbon Each is independently selected from aryl groups having a number of 6 or more and 12 or less.

  Specific examples of the sulfonic acid ester include at least one of 1,3-propane sultone and 1,4-butane sultone. Further, at least one cyclic disulfonic acid ester selected from methylene methane disulfonate, ethylene methane disulfonate, and propylene methane disulfonate is exemplified, but the invention is not limited thereto.

  Among these compounds, mention may be made of methylene methane disulfonate represented by the following compound 1, ethylene methane disulfonate represented by compound 2, cyclic compounds such as compound 3 to compound 9, and 1,3-propane of compound 10. Can do.

  Moreover, you may add multiple types for the additive for EI formation. For example, a sultone compound of Compound 10 may be added to Compound 1 to Compound 9. A vinylene carbonate compound may be added. This improves the stability of the coating (SEI) formed on the surface of the negative electrode (active material particles), suppresses the decomposition of the aprotic organic solvent contained in the electrolyte or polymer gel electrolyte, The effect of preventing deterioration of characteristics due to moisture becomes remarkable (increases), which is excellent in that cycle characteristics are improved, cell swelling is suppressed, and internal resistance is suppressed.

  The additive for SEI formation such as the cyclic disulfonic acid ester of the present invention forms a film (SEI) on the electrode of the non-aqueous electrolyte secondary battery. That is, SEI-forming additives such as sulfonic acid ester compounds can form a coating (SEI) before the aprotic organic solvent contained in the electrolyte solution or polymer gel electrolyte is decomposed. Since the decomposition of the aprotic organic solvent is suppressed, the swelling of the battery due to the generation of gas due to the decomposition can be suppressed and the rate characteristics can be improved. In addition, when the positive electrode (active material layer) contains a lithium manganese complex oxide (positive electrode active material) such as lithium manganate, manganese eluted in the electrolyte or gel electrolyte is adsorbed on the surface of the negative electrode (active material particles). Can be prevented. As a result, it is effective for suppressing a decrease in rate characteristics due to an increase in resistance and improving cycle characteristics.

  The SEI-forming additive is desirably in the range of 0.5 to 2.0% by mass with respect to the total amount of solid content of the negative electrode slurry (component of the negative electrode active material layer). Within this range, regardless of the thickness direction, the SEI formed by the negative electrode active material surface near the negative electrode current collector inside the electrode and the negative electrode active material surface near the electrode (negative electrode active material layer) outside. High-quality (uniform thickness) SEI can be formed without causing a problem that the thicknesses of the layers are different (see FIGS. 7 to 10 and FIGS. 11 to 14). One purpose of the initial charging process is the formation of SEI. If there is an additive for SEI formation in the electrolytic solution, it is necessary to move the additive in the electrolytic solution on the positive electrode side to the negative electrode side to form SEI at the time of initial charging. The time will be longer. Further, after that, as shown in FIG. 4, although it is necessary to perform high temperature aging over 14 days or more, and room temperature aging for 14 days or more, there is a problem that quality variation occurs as shown in FIG. there were. By adding the SEI-forming additive within the above range to the negative electrode slurry, it is possible to obtain a configuration in which the SEI formation additive is not added to the electrolytic solution and the positive electrode slurry, which is excellent in that the above-described problems can be solved.

  Furthermore, in the present invention, an aqueous solvent (such as water) can be used in place of the slurry viscosity adjusting solvent (such as NMP) in the negative electrode slurry containing the SEI forming additive described above. The method for preparing a negative electrode slurry using an aqueous solvent (such as water) is not particularly limited. For example, in addition to the negative electrode active material and the SEI forming additive, an aqueous binder, a CMC or CMC salt that is a thickener, and a conductive aid if necessary are mixed, and then the negative electrode is used with an aqueous solvent such as water. A slurry (aqueous slurry) can be prepared.

Further, in the negative electrode slurry (aqueous slurry) using the aqueous solvent, it is desirable to add alkaline water before application to the current collector or after application described later. Here, the alkaline water is not particularly limited, and lithium hydroxide aqueous solution, sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, rubidium aqueous solution, cesium hydroxide aqueous solution, beryllium hydroxide aqueous solution, magnesium hydroxide aqueous solution. , A calcium hydroxide aqueous solution, a strontium hydroxide aqueous solution, a barium hydroxide aqueous solution, an ammonium hydroxide aqueous solution, etc., but are not limited to these. These may be used alone or in combination of two or more. Of these, an aqueous lithium hydroxide solution is preferred. In this case, CMC or CMC salt contained as a thickener can be reduced (decarboxylated) to form a CMC derivative. In addition, by selecting a lithium hydroxide aqueous solution as the alkaline water, lithium carbonate can be formed on the surface of the negative electrode active material (particles) or on the surface of the CMC derivative scattered or coated on the negative electrode active material (particles) surface. Specifically, lithium carbonate (Li ₂ CO ₃ ) can be scattered in a granular form, or a lithium carbonate film can be formed. Thereby, the initial charge / discharge efficiency can be increased. Furthermore, generation of gas can be further suppressed. Further, since this lithium carbonate is also a component of the SEI (protective film) of the negative electrode active material, it is excellent in that the life performance can be improved in addition to the gas generation suppressing effect and the capacity increasing effect. Scattering of lithium carbonate on the surface of the coating of the CMC derivative or coating of lithium carbonate may be performed by initial charge / discharge as well as during the production of the negative electrode. Specifically, since the SEI (protective film) can be formed on the surface of the negative electrode active material (particles) by a side reaction during the first charge / discharge, the active material (part of the battery capacity) is used for the surface film. The capacity of was decreasing. However, since such SEI (protective film) can be formed in advance in the electrode manufacturing stage by selecting a lithium hydroxide (LiOH) aqueous solution, the initial charge / discharge efficiency can be increased. In other words, loss at the first charge / discharge can be suppressed.

  The alkali concentration added to the negative electrode slurry using the aqueous solvent is such that the alkali metal / alkaline earth metal content of the alkaline component is the total amount of the negative electrode active material layer (corresponding to the negative electrode active material layer raw material). It is in the range of 50 to 30000 ppm, preferably 100 to 20000 ppm. However, even if it is out of the above range, it can be sufficiently applied as long as the effects of the present invention can be effectively expressed. When the content of the alkali metal and / or alkaline earth metal is 50 ppm or more, an effective content effect for improving the charge / discharge capacity is recognized. Moreover, if it is 30000 ppm or less, it is advantageous at the point which can contribute to the improvement of charging / discharging capacity.

  The alkali concentration in the alkaline water is not particularly limited, but may be in the range of pH 9 to 14, preferably pH 12 to 14. If the alkali concentration is within the above range, CMC or CMC salt contained as a thickener can be reduced (decarboxylated) to form a CMC derivative. Thereby, the initial charge / discharge efficiency can be increased. Furthermore, gas generation can be further suppressed. In addition, although the said pH is based also on the mixing | blending of aqueous slurry, it is good to aim at the isoelectric point of these mixing | blendings. That is, it can be said that an alkali or alkaline water in an amount capable of completely reducing CMC or CMC salt in the aqueous slurry may be added.

  The addition amount of the alkaline water is not particularly limited, but may be in the range of 0.1 to 10% by mass with respect to the aqueous slurr. If it is in the said range, CMC thru | or CMC salt contained as a thickener can be reduced (decarboxylation) reaction, and can be made into a CMC derivative.

  Next, in a battery (power generation element) formed using a negative electrode slurry containing the SEI formation additive of the present invention and a battery (power generation element) into which an electrolyte containing a conventional SEI formation additive was injected The influence on the battery performance due to the difference in the SEI formation process will be described with reference to the drawings.

  First, FIG. 6A is a schematic cross-sectional view showing the influence of a coating derived from a solvent in an electrolytic solution or gel electrolyte, and FIG. 6B is a schematic cross-sectional view showing the influence of a coating derived from an additive for SEI formation. FIG. 7 is a schematic cross-sectional view of an electrode schematically showing a state immediately after injection of an electrolyte in a SEI formation process derived from an additive for SEI formation in a conventional electrolyte (Patent Document 1) or gel electrolyte. . FIG. 8 is a schematic cross-sectional view of an electrode schematically showing a state immediately after the first charge in the SEI formation process derived from the additive for SEI formation in the conventional electrolyte solution or gel electrolyte (Patent Document 1). FIG. 9 is an electrode schematically showing a state in which SEI starts to be formed on the outside of the negative electrode by initial charging in the SEI formation process derived from the additive for SEI formation in the conventional electrolyte solution or gel electrolyte (Patent Document 1). FIG. FIG. 10 shows that the additive in the electrolyte solution of the positive electrode moves to the negative electrode side by the initial charge in the SEI formation process derived from the SEI formation additive in the conventional electrolyte solution or gel electrolyte, and the negative electrode inner side. It is the electrode cross-sectional schematic which represented typically a mode that SEI was formed. FIG. 11 is a schematic cross-sectional view of a negative electrode electrode schematically showing a state in which the negative electrode slurry is dried in the SEI formation process derived from the SEI formation additive in the negative electrode slurry of the present invention. FIG. 12 is a schematic cross-sectional view of an electrode schematically showing a state before injection of an electrolytic solution in the SEI formation process derived from the SEI formation additive in the negative electrode slurry of the present invention. FIG. 13 is a schematic cross-sectional view of an electrode schematically showing a state after injection of an electrolytic solution in the SEI formation process derived from the SEI formation additive in the negative electrode slurry of the present invention. FIG. 14 is a schematic cross-sectional view of an electrode schematically showing the state after the initial charge in the SEI formation process derived from the SEI formation additive in the negative electrode slurry of the present invention.

  First, as shown in FIG. 6A, when there is no SEI formation additive, solvent molecules (for example, EC, PC, DEC, DMC, etc.) in the electrolytic solution or gel electrolyte on the surface of the negative electrode 57 at the time of initial charge. Is decomposed to form a high-resistance film 58 derived from the solvent. That is, in the absence of the SEI forming additive, the decomposition of the electrolytic solution on the surface of the negative electrode 57 proceeds during the initial charge, and the battery life is reduced due to the depletion of the electrolytic solution. The internal resistance of the battery increased, and part of the extracted current was lost due to resistance heat generation, leading to a decrease in battery capacity. In the present invention, as shown in FIG. 6B, by adding the SEI formation additive, it is possible to generate the SEI 59 derived from the SEI formation additive on the surface of the negative electrode 57 during the initial charge. it can. SEI 59 derived from the SEI forming additive can suppress an increase in the internal resistance of the battery, further suppress the decomposition of solvent molecules in the electrolyte solution or gel electrolyte on the surface of the negative electrode 57, and improve the battery life. It is.

  Next, in the SEI formation process derived from the SEI formation additive in the conventional electrolyte solution (or gel electrolyte) shown in FIG. 7, immediately after the injection of the electrolyte solution, the SEI formation additive 18 is contained in the electrolyte solution or gel electrolyte. And is impregnated from the outside of the positive and negative electrode active material layers 13 and 15. Accompanying the impregnation with the electrolytic solution or gel electrolyte, it adheres to the surfaces of the positive electrode and negative electrode active material particles 14 and 16 in the positive electrode and negative electrode active material layers 13 and 15. Therefore, regardless of the positive electrode active material layer 13 and the negative electrode active material layer 15, they are uniformly contained in the electrolytic solution (or gel electrolyte). As shown in FIG. 7, the outer side of the active material layers 13 and 15 is good and the inner side (current collectors 11 and 12 side) is poor in the impregnation property of the electrolytic solution containing the SEI forming additive 18. In FIG. 7, the outside of the active material layers 13 and 15 impregnated with the electrolyte solution containing the SEI forming additive 18 is highly concentrated because the concentration of the electrolyte solution and the SEI forming additive 18 is also high. It is displayed in color and shows that a large amount of SEI forming additive 18 is also adhered. On the other hand, the inside of the active material layers 13 and 15 that are poorly permeable to the electrolyte solution containing the SEI forming additive 18 and not so impregnated has a low concentration because the concentration of the electrolyte solution and the SEI forming additive 18 is low. It shows that the additive 18 for SEI formation is attached only a little.

Next, in the SEI formation process derived from the additive for SEI formation in the conventional electrolyte solution (or gel electrolyte) shown in FIG. 8, immediately after the first charge, Li ions 20 are transferred along with the movement of electrons (e ⁻ ) by the charger 22. The state of moving from the positive electrode side 13 to the negative electrode side 15 via the electrolyte layer 17 is shown.

  Further, the SEI formation process derived from the SEI formation additive in the conventional electrolyte or gel electrolyte shown in FIG. 9 shows that the SEI 18a has started to be formed outside the negative electrode 15 by the initial charge. That is, by the first charge, the SEI forming additive 18 in the electrolytic solution (or gel electrolyte) starts to electrolyze on the surface (outside) of the negative electrode active material layer 15 to form the SEI 18a, but the electrolytic solution has good permeability. A mode that it forms from the outer side of the negative electrode active material layer 15 is represented. At this time, on the positive electrode active material layer 13 side, the SEI forming additive 18 in the electrolytic solution (or gel electrolyte) is not electrolyzed, and thus remains as it is.

  Finally, in the SEI formation process derived from the SEI formation additive in the conventional electrolyte solution or gel electrolyte shown in FIG. 10, the additive 18 in the electrolyte solution on the positive electrode side 13 is transferred to the negative electrode side 15 as the initial charge progresses. The SEI 18a is also formed inside the active material layer 15 (current collector 12 side). Since the SEI 18a becomes a resistance component, a uniform composition and a uniform distribution (that is, a uniform thickness regardless of the thickness direction of the active material layer 15) are important in battery performance. In the SEI formation process derived from the SEI formation additive in the conventional electrolyte solution or gel electrolyte shown in FIG. 10, high temperature aging and further normal temperature aging are both performed for 14 days or more after the initial charge, so The SEI forming additive 18 in the liquid (or gel electrolyte) moves to the negative electrode side 15. Thus, the SEI 18 a is formed on the surface of the negative electrode active material particles 16 inside the negative electrode active material layer 15 by moving the SEI forming additive 18 on the positive electrode side 13 to the negative electrode side 15 over a long time. However, at the same time, the SEI 18a on the surface of the negative electrode active material particles 16 outside the negative electrode active material layer 15 also grows and becomes a thicker film. Therefore, the SEI 18a having a uniform thickness cannot be formed regardless of the thickness direction of the negative electrode active material layer 15 which is important for battery performance. In addition, in order to form the SEI 18a also on the surface of the negative electrode active material particles 16 inside the negative electrode active material layer 15, it is necessary to perform aging at a high temperature for a very long period after the initial charge, and the production efficiency is extremely low and the cost is high. It was one of the causes. The high temperature aging is usually performed at 40 to 80 ° C. for about 14 to 30 days so that the voltage of the battery after aging becomes a desired level. Room temperature aging is also usually performed at room temperature for about 14 to 30 days.

  On the other hand, the SEI formation process derived from the additive for SEI formation in the negative electrode slurry of the present invention shown in FIG. 11 shows the state of drying of the negative electrode slurry. A negative electrode slurry containing the SEI forming additive 18 is applied onto the current collector foil 12 and then dried to form a dry coating film. The additive 18 dissolved in the viscosity adjusting solvent 9 is present in the form of a solution in the negative electrode slurry coating (wet state) 15 ′ immediately after coating. Therefore, by drying the negative electrode slurry coating film 15 ′, the viscosity adjusting solvent 9 evaporates from the negative electrode slurry coating film 15 ′, so that the dissolved additive 18 is dried and solidified. Because of its crystallinity, it is deposited on the surface of the active material particles 16 in the coating film 15 '. Thereby, in the dry coating film of the portion where the viscosity adjusting solvent 9 has evaporated, the additive 18 is uniformly deposited on the entire surface of the active material particles 16 regardless of the thickness direction. That is, the distribution of the SEI forming additive 18 can be uniformly present on the outside and the inside of the dried coating film after drying (the negative electrode active material layer 15; see FIG. 12). At this time, the additive 18 is not present on the positive electrode side 13.

  Next, in the SEI formation process derived from the additive for SEI formation in the negative electrode slurry of the present invention shown in FIG. 12, the state before injection of the electrolytic solution is shown. The negative electrode is formed by adding the SEI forming additive 18 to the negative electrode slurry. Therefore, the SEI forming additive 18 is attached only to the surface of the negative electrode active material 16 in the negative electrode active material layer 15. Further, the SEI forming additive 18 is uniformly attached to the surface of the negative electrode active material particles 16 regardless of the thickness direction of the negative electrode active material layer 15. That is, it can be seen that the distribution of the SEI forming additive 18 can be uniformly present between the outer side and the inner side of the negative electrode active material layer 15 without variation. At this time, the additive 18 is not present on the positive electrode side 13.

  Therefore, in the SEI formation process derived from the SEI formation additive in the negative electrode slurry of the present invention shown in FIG. 13, the additive 18 that crystallizes and adheres to the surface of the negative electrode active material particles 16 after the injection of the electrolytic solution. The surface of the active material 16 particles is coated by dissolving in a solvent in the electrolytic solution. At this time, the distribution of the additive 18 coated on the surface of the negative electrode active material particles 16 on the outer side and the inner side of the active material layer 15 does not vary, and all the negative electrode active materials in the active material layer 15 (the entire region from the inner side to the outer side). It can be seen that the particles 16 can be uniformly present (coated) on the surface. On the other hand, the additive 18 does not exist on the positive electrode side 13 even after the injection.

  Finally, the SEI formation process derived from the SEI formation additive in the negative electrode slurry of the present invention shown in FIG. 14 shows the state after the initial charge. In the present invention, the SEI 18a derived from the additive 18 that is uniformly coated on the surface of the negative electrode active material 16 particles in the active material layer 15 can be formed by the initial charging. Therefore, a uniform SEI 18a can be formed in a short time in the entire area of the active material layer 15 (from the outside to the inside) regardless of the thickness of the active material layer 15 of the negative electrode. This is because the additive 18 is already uniformly coated on the surface of the negative electrode active material particles 16, so that it is not necessary to move and the SEI 18 a can be generated quickly.

  In addition, the volume of the negative electrode active material particles 16 expands and contracts due to the charge / discharge cycle after the first charge / discharge. By doing so, the surface layer of the active material particle 16 is cracked by internal stress applied to the active material 16 particle itself and / or compressive stress applied by the surrounding active material particles 16 in the electrode 15. Newly active nascent surfaces are created. When the additive 18 is included in the electrolytic solution as in the prior art, the thickness of the SEI 18a varies between the outside and inside of the active material layer 15, as shown in FIG. On the current collector 12 side, the SEI 18a is hardly formed, or even if it is formed, the film thickness is extremely thin compared to the thick film of the SEI 18a formed on the outer active material particle 16 surface. Yes. Therefore, the formation of SEI 18a on the inner surface of the active material layer 15 becomes more difficult with respect to the nascent surface, which is a factor that promotes battery deterioration. On the other hand, in the present invention, by including the SEI forming additive 18 in the negative electrode slurry, the SEI 18a having a uniform thickness is formed on the outside and inside of the active material layer 15, as shown in FIG. Therefore, a good quality SEI 18a can be quickly formed in the entire area (outside and inside) of the active material layer 15 even on the raw surface caused by the expansion / contraction of the active material 16 particles by charging / discharging, and the battery deterioration is effective. It is excellent in that it can be prevented.

(Solvent contained in negative electrode slurry)
The slurry viscosity adjusting solvent is not particularly limited, and examples thereof include N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, and methylformamide.

  Further, the aqueous solvent as the viscosity adjusting solvent is not particularly limited, and a conventionally known aqueous solvent can be used. For example, water (specifically, pure water, ultrapure water, distilled water, ion exchange water, ground water, well water, tap water (tap water), etc.), water and alcohol (eg, ethyl alcohol, methyl alcohol, isopropyl alcohol) Etc.) can be used. However, in the present embodiment, the present invention is not limited to these, and conventionally known aqueous solvents can be appropriately selected and used as long as the effects of the present embodiment are not impaired.

(Viscosity of negative electrode slurry)
The viscosity of the negative electrode slurry is not particularly concerned and can be applied in a wide viscosity range. Here, as a viscosity of the negative electrode slurry in this embodiment, Preferably it is 500-10000 mPa * s, More preferably, it is 800-9000 mPa * s, More preferably, it is 1000-8000 mPa * s. When the viscosity of the negative electrode slurry is 500 mPa · s or more, the negative electrode slurry can be uniformly applied to a predetermined thickness on the current collector foil to be conveyed using a coating machine (coater or the like). In the negative electrode obtained as a result, a negative electrode active material layer having a uniform and flat surface can be formed. If the viscosity of the negative electrode slurry is 100000 mPa · s or less, the negative electrode slurry can be uniformly applied to a predetermined thickness on the current collector foil conveyed using a coating machine (coater or the like), and then Can be dried in a short time. In the negative electrode obtained as a result, a negative electrode active material layer having a uniform and flat surface can be formed.

(2) Negative electrode raw material production process ("application / drying" process 2b + "press" process 2c in FIG. 4)
This step is not particularly limited as long as the obtained negative electrode slurry can be applied to the surface of the current collector, dried and pressed to produce the negative electrode raw material, and a conventionally known method is applied. Can do.

(Current collector; negative electrode current collector foil)
The current collector is as described above. In addition, when used for production of the negative electrode raw material, a metal thin film (a metal foil made of a material and a thickness used for a current collector, for example, a copper foil having a thickness of 10 μm, etc.) is used in the same manner as a conventionally known manufacturing method Is preferably purchased as a roll and used as a negative electrode current collector foil.

(Slurry application)
The method of applying the negative electrode slurry to the surface of the current collector that is continuously conveyed while being unwound from the negative electrode current collector foil attached to the unwinding roller is not particularly limited, and a conventionally known method is applied. Can do. For example, as a method capable of continuously applying the negative electrode slurry onto the continuously conveyed current collector, for example, a coating method using various coaters such as a die, a patterning coating method such as an ink jet method or a screen printing coating method is used. be able to. In the slurry application, it is desirable that the coating is generally performed so that the basis weight or the accuracy of the application mass is within a range of about ± 5% by mass (any part).

(Conveying means)
As the current collector foil conveying means, a conventionally known conveying means can be used. For example, it is possible to use a guide roll or the like provided at regular intervals so that the current collector foil traveling between the winding roll and the winding roll can be stably conveyed. Absent. With respect to the guide roll, the current collector foil and further the negative electrode slurry applied on the current collector foil are passed through a coating machine (coater), a drying device (drying furnace), and further a roll press device and conveyed. It is provided for. For this reason, an appropriate number is appropriately arranged at the locations necessary for passing and transporting around and inside the various devices described above. In other words, other than the guide rolls, various well-known conveying means are appropriately used, not shown. By using such a conveying means, the production speed can be increased while suppressing the equipment cost, and the negative electrode active material layer can be produced while reducing the cost.

(Drying; Removal of slurry viscosity adjusting solvent)
Next, the current collector on which the negative electrode slurry coating film has been formed is dried to remove the slurry viscosity adjusting solvent or aqueous solvent contained in the slurry coating film. The drying conditions are not particularly limited, and conventionally known production methods can be applied. Specifically, the drying conditions are determined according to the applied negative electrode slurry and cannot be uniquely defined, but are usually 40 to 150 ° C., preferably 80 to 130 ° C., and 5 minutes to 20 hours. The drying atmosphere is not particularly limited, and is preferably performed in an air atmosphere from the viewpoint of production cost, but is not limited thereto. As the drying means (apparatus), a drying means using hot air drying and infrared (IR) drying capable of normal continuous drying can be used, and a drying means using vacuum drying can also be used. Moreover, you may use the drying means which used hot air drying and IR drying together.

  The above application and drying are performed on the current collector surface (A surface), and then the other surface (B surface) of the current collector is applied and dried in the same manner on both surfaces of the current collector. A dry coating film can be formed. In addition, you may perform the said application | coating and drying simultaneously for both A surface and B surface. In the case where the application and drying are performed simultaneously on both the A side and the B side, from the viewpoint of preventing the slurry on the lower side from dripping, the current carrying direction of the current collector is changed from the horizontal direction to the vertical direction (from top to bottom). Alternatively, the method may be performed from the bottom to the top). In this case, a conveying device, a coating (coating) device, a drying device, and the like may be installed from horizontal to vertical (or from vertical to horizontal). In the case of a bipolar electrode, a dry coating film (positive electrode active material layer) is formed on the A surface (or B surface) using the positive electrode slurry, and the negative electrode slurry is used on the B surface (or A surface). A dry coating film (negative electrode active material layer) may be formed. Also in this case, the application and drying may be performed in the order of the A surface and the B surface, or the application and drying may be performed simultaneously on both the A surface and the B surface.

(Dry coating press)
Next, by pressing the current collector having the dried coating film after drying the starry coating film and adjusting the slurry dry coating film (positive electrode active material layer) to have a target density, obtain.

The press conditions are not particularly limited, and conventionally known production methods can be applied. Specifically, the slurry dry coating film (negative electrode active material layer) is within a target density range of 0.90 to 1.10 g / cm ³ by roll press while continuously transporting a current collector having a dry coating film on both sides. It is desirable to adjust as follows. However, the present invention is not limited to the above target density range, and may be appropriately determined in consideration of the purpose of use of the battery (output importance, energy importance, etc.), ion conductivity, and the like. The press method may be either a cold press or a hot press.

  In addition, the collector which has a dry coating film can be normally obtained as a roll-shaped negative electrode original fabric by winding on a winding roller, after being roll-pressed, carrying continuously. Preferably, the negative electrode fabric (current collector having a dry coating film) to be conveyed after the pressing may be cut by the following cutting means without being wound by a winding roller.

(3) Negative electrode manufacturing step (“slit” step 2d in FIG. 4)
In this step, the negative electrode raw material obtained above is cut (cut) into a desired shape and size using a cutting means, and dried to obtain a negative electrode.

(Cut negative electrode fabric (cutting))
The method for cutting the negative electrode raw material obtained above into a desired shape and size using an appropriate cutting means is not particularly limited, and conventionally known production methods can be applied. Specifically, the negative electrode raw material wound up in a roll shape by the take-up roller obtained above is attached to the unwinding roller again, and the negative electrode raw material is not unwound so that a cutting means such as a slitter is used. Then, it may be cut into a rectangular shape in accordance with the desired shape and size, specifically the target negative electrode size. The cutting means is not limited to the slitter and the like, and conventionally known cutting means can be used as appropriate. Preferably, the target negative electrode size using a cutting means such as a slitter is applied to the negative electrode fabric (current collector having a dry coating film) conveyed after the pressing step without being wound by a winding roller. It is desirable to cut it into a rectangular shape or the like according to the point of reducing the man-hours.

(Drying; removal of adhering water)
Next, the cut negative electrode is dried to remove moisture adhering to the negative electrode raw material preparation step (2). The drying conditions are not particularly limited, and conventionally known production methods can be applied. Specifically, the drying conditions are determined according to the size of the negative electrode and cannot be uniquely defined. Usually, however, drying is performed at 70 ° C. or higher for 7 hours or longer using a vacuum dryer. The drying atmosphere is not particularly limited, but it is desirable to perform vacuum drying under reduced pressure after substitution with an inert gas (nitrogen gas), but is not limited thereto. As the drying means (apparatus), a drying means using a vacuum drying apparatus can also be used. Moreover, you may use the drying means which used vacuum drying and IR drying together. Through the drying, a negative electrode having a desired target density, size, and shape can be obtained.

[III] Step of Forming the Laminate (“Lamination / Tab Welding” Step 3a in FIG. 4)
In this step [III], the positive electrode and the negative electrode obtained in the positive electrode forming step [I] and the negative electrode forming step [II], and a separator are laminated to form a laminate.

(Method for forming laminate)
The positive electrode and the negative electrode obtained in the positive electrode forming step [I] and the negative electrode forming step [II], and a separator are alternately stacked in the order of a positive electrode, a separator, a negative electrode, a separator, and a positive electrode. By doing so, it can be set as the laminated body which consists of desired lamination | stacking number (cell number) (refer the electric power generation element 21 of FIG. 1, and FIG. 4).

  Here, the separator is obtained in the same manner as the positive electrode and the negative electrode, for example, by purchasing a microporous film (thickness of about 25 μm) made of polyethylene (PE) or the like with a roll. It is desirable to cut (cut) the raw material of the separator into a desired shape and size using a cutting means, and obtain the separator through drying.

(Separator material cut (cut))
The method of cutting the separator raw fabric into a desired shape and size using an appropriate cutting means is not particularly limited, and conventionally known production methods can be applied. Specifically, the separator roll wound up in a roll is attached to the unwinding roller, and since the separator blank is unwound, using a cutting means such as a slitter, the desired shape, size, and in detail What is necessary is just to cut into a rectangular shape according to the separator size. The cutting means is not limited to the slitter and the like, and conventionally known cutting means can be used as appropriate.

(Drying; removal of adhering water)
Next, the cut separator is dried to remove the attached moisture. The drying conditions are not particularly limited, and conventionally known production methods can be applied. Specifically, the drying conditions are determined according to the separator size and the like and cannot be uniquely defined. Usually, however, the drying is performed at 70 ° C. or higher for 7 hours or longer using a vacuum dryer. The drying atmosphere is not particularly limited, but it is desirable to perform vacuum drying under reduced pressure after substitution with an inert gas (nitrogen gas), but is not limited thereto. As the drying means (apparatus), a drying means using a vacuum drying apparatus can also be used. Moreover, you may use the drying means which used vacuum drying and IR drying together. Through the above drying, a separator having a desired target density, size, and shape can be obtained.

(Lamination method)
The lamination of the positive electrode, the separator, and the negative electrode is not particularly limited, and may be performed manually or may be automated (mechanical). For automation (mechanization), a commercially available lamination machine may be used, or an in-house produced lamination machine may be used.

(Outline of laminate)
FIG. 15 is an exploded perspective view schematically showing the basic configuration of the laminate. 15 uses 16 positive electrodes 62, 17 negative electrodes 63, and 32 separators 64, and in order from the top, negative electrode 63, separator 64, positive electrode 62, separator 64,... Are laminated.

(Tab welding)
Next, as shown in FIG. 15, the positive electrode tab 62a and the negative electrode tab 63a are joined to the said laminated body 61 (each collector of it; not shown) by welding. If necessary, it is desirable to remove excess tabs and the like by trimming after welding. Such a joining method is not particularly limited, but the ultrasonic active machine does not generate heat (heat) at the time of joining and can be joined in a very short time, so that the electrode active material layer is deteriorated by heat. It is excellent in that it can be prevented. At this time, as shown in FIG. 15, the positive electrode tab 62a and the negative electrode tab 63a can be arranged so as to face each other (opposite) on the same side (the same extraction side). Thus, the positive electrode tabs 62a of the positive electrodes 62 (16 sheets) are bundled into one positive current collector plate (positive electrode current collector tab: reference numeral 62A in FIG. 18; reference numeral 25 in FIG. 1, reference numeral 48 in FIG. 3) ) Can be taken out from the exterior body. Similarly, the negative electrode tab 63a of each negative electrode 63 (17 sheets) is bundled into one negative current collector plate (negative current collector tab: reference numeral 63A in FIG. 18; reference numeral 27 in FIG. 1, reference numeral 49 in FIG. 3) Can be taken out from the exterior body. However, as shown in FIGS. 1 and 3, the positive electrode current collector plate (positive electrode current collector tab) and the negative electrode current collector plate (negative electrode current collector tab) are arranged on opposite sides (different extraction sides). The tab 62a and the negative electrode tab 63a may be arranged, and is not particularly limited.

  As described with reference to FIG. 2, an adhesive layer may be formed on the separator and stacked. As a result, even if the electrode (positive electrode or negative electrode) and the separator are stacked, they can be stably stacked without shifting. Therefore, an inspection item is provided so that the electrode does not protrude from the separator at the end and cause a short circuit. This is superior in that it eliminates the trouble of inspecting for misalignment.

[IV] A step of injecting an electrolyte into the laminate (“injection” step 3b in FIG. 4)
In this step, an electrolytic solution is injected into the laminate. FIG. 16 is a drawing schematically showing a state in which the laminate is sandwiched (stored) from above and below by a laminate film used for a battery exterior body. FIG. 17 is a drawing schematically showing a state of a three-side sealed body in which a laminated body is housed in an exterior body and three sides of the exterior body are sealed. FIG. 18 is a drawing schematically showing a device configuration for injecting an electrolytic solution from the opening on one side where the three-side sealing body remains.

(Storing the laminated body in an exterior material; preparation stage 1 before injection)
First, as shown in FIG. 16, a laminate film 65 using the laminated body 61 as a battery exterior body has a positive electrode current collector plate (positive electrode current collector tab) 62 </ b> A and a negative electrode current collector plate (negative electrode current collector tab) 63 </ b> A from above and below. Insert the battery so that it can be taken out of the battery case. Next, as shown in FIG. 17, three sides of the outer peripheral portions (sealing portions) 66 of the upper and lower laminate films 65 are sealed by thermocompression bonding. An insulating reinforcing sheet 67 is provided on the inner side of the upper and lower laminate films 65 where the positive electrode current collector plate (positive electrode current collector tab) 62A and the negative electrode current collector plate (negative electrode current collector tab) 63A are taken out. May be. As a result, even if an unexpected accident such as an unexpected strong vibration or impact, or a user accidentally scratching with a blade during use, part of the upper and lower laminate films 65 is damaged, It is possible to prevent the Al foil from being exposed. As a result, the positive electrode current collector plate (positive electrode current collector tab) 62A and the negative electrode current collector plate (negative electrode current collector tab) 63A do not come into contact with the Al foils in the upper and lower laminate films 65, and the safety of the battery is remarkably increased. It is excellent in that it can be increased.

(Preparation of three-side sealed body; preparation stage 2 before injection)
By sealing and sealing three sides of the outer peripheral portions (heat sealing portions) 66 of the upper and lower laminate films 65, the laminate (not shown) is stored in the exterior body 65a as shown in FIG. And the 3 side sealing body 71 which sealed 3 sides (heat sealing part 66a) among the outer peripheral parts (sealing part 66) of the exterior body 65a can be obtained. 16 indicates a state before sealing by thermocompression bonding (a state where the upper and lower laminate films 65 are not thermally bonded and bonded). The thermocompression bonding part 66a in FIG. 17 refers to a state after thermocompression bonding and sealing (a state in which the upper and lower laminate films 65 are heat-sealed and bonded). At this time, it is preferable to seal the heat sealing portion 66 on the side where the positive electrode current collecting plate (positive electrode current collecting tab) 62A and the negative electrode current collecting plate (negative electrode current collecting tab) 63A are taken out. This is because when the positive electrode current collector plate (positive electrode current collector tab) 62A and the negative electrode current collector plate (negative electrode current collector tab) 63A are in the opening at the time of the subsequent injection, the electrolyte scatters at the time of injection. Because there is a fear.

(Liquid injection)
In the liquid injection device 81 shown in FIG. 18, an electrolyte storage tank (not shown) is provided inside the three-side sealing body 71 from the remaining one side opening 68 of the three-side sealing body 71 before the injection. The electrolyte solution is injected from an injection nozzle 85 provided at the tip of the electrolyte solution transport line 83 connected to. As a result, an electrolyte layer in which the separator is impregnated with the electrolytic solution is formed. At this time, the three-side sealing body 71 is connected to a vacuum pump (not shown) so that the electrolyte can be impregnated in the laminate inside the three-side sealing body 71, particularly the separator and the electrode active material layer as soon as possible. It is desirable to carry out liquid injection in a state where the vacuum box 87 is housed and the pressure is reduced and the inside is in a high vacuum state. After the injection, the three-side sealing body 71 is taken out from the vacuum box 87, and the remaining one side of the three-side sealing body 71 is sealed (heat-sealed) to form a laminate type (laminated structure) lithium ion secondary battery. May be completed. The electrolytic solution used in this step is as already described.

  Furthermore, in the present invention, it is desirable that the electrolytic solution does not contain an additive for forming SEI. Thereby, the negative electrode active material surface in the vicinity of the negative electrode current collector inside the electrode and the negative electrode active material surface in the vicinity of the electrode (negative electrode active material layer) outside do not cause a problem that the thickness of the formed SEI is different. (For comparison, see FIGS. 7 to 10 and FIGS. 11 to 14). One purpose of the initial charging process is the formation of SEI. If there is an additive for SEI formation in the electrolytic solution, it is necessary to move the additive in the electrolytic solution on the positive electrode side to the negative electrode side to form SEI at the time of initial charging. The time will be longer. Furthermore, as shown in FIG. 4, although it is necessary to perform high temperature aging over 14 days or more as shown in FIG. 4, there is a problem that quality variation occurs as shown in FIG. In the manufacturing method of this invention, it is excellent at the point which can eliminate the above-mentioned subject by setting it as the structure which adds the additive for SEI formation to a negative electrode slurry, and does not add to electrolyte solution and a positive electrode slurry.

  However, in the present invention, after the step [IV], as shown in FIG. 4, the following steps may be performed. In this case, the remaining one side of the three-side sealing body 71 is not sealed (thermally sealed), but can be opened and closed by a clip or the like, and the gas generated by precharging or initial charging can be discharged from the exterior body. It is desirable to do so.

  A first impregnation step [V] for impregnating the electrolyte that has been allowed to stand for a certain period of time, a pre-initial charge step [VI] for performing the pre-initial charge, and a first step for promoting impregnation of the electrolyte by leaving for a certain period of time. 2 It is desirable to include an impregnation step [VII] and an initial charging step [VIII] for performing initial charging. By including these steps, the electrolytic solution is thoroughly impregnated, and charge / discharge cycles after the initial discharge can be performed without impairing the battery reaction area. Further, as shown in FIG. 4, in the manufacturing method of the present invention, since the SEI formation additive is included in the negative electrode slurry, the SEI formation is formed in a short time as described with reference to FIGS. The formation of SEI can be completed without performing high-temperature aging for 14 days or more after the initial charging step and, further, room temperature aging for 14 days or more as required. Furthermore, a large amount of gas generated at the time of pre-initial charge or initial charge (almost no gas is generated during the initial discharge or the subsequent charge / discharge cycle) can be easily discharged. Hereinafter, step [V] and subsequent steps will be described.

[V] First impregnation step (“impregnation” step 3c in FIG. 4)
In this step, it is only necessary that the three-side sealed body after the injection is allowed to be impregnated with the electrolyte that has been allowed to stand for a certain period of time, and is not particularly limited, and a conventionally known method can be applied. . Usually, the electrolytic solution poured from the opening is impregnated into the separator and the active material layer by leaving it to stand for about 1 to 24 hours. Depending on the case, it may be performed in an environment in which the battery is easily impregnated with the electrolytic solution by repeating the pressurization and depressurization using the vacuum box 87 or the vacuum pump used in the liquid injection process. Also, the atmosphere is preferably performed in a dry environment containing no moisture, for example, in a dry inert gas atmosphere. Moreover, depending on the case, you may make it accelerate | stimulate that an electrolyte solution is impregnated by applying the gentle ultrasonic vibration of the grade which does not destroy an electrode. In addition, by sufficiently impregnating the electrolyte not only outside the electrode but also inside the electrode (current collector side), as described above, from the outside of the electrode to the inside ( It is also excellent in that uniform SEI can be formed up to the current collector side.

[VI] Pre-initial charging step ("impregnation" step 3d in FIG. 4)
In this step, it is only necessary to perform pre-initial charging at a predetermined charging rate after the remaining one side of the three-side sealing body after the first impregnation step is closed with a clip, and is not particularly limited. A known method can be applied. Usually, it may be performed at a charge rate of 0.1 C to 1.0 C for about 0.5 to 1.0 hour. As a result, defective products can be easily found and removed. Moreover, as shown in FIG. 4, formation of uniform SEI can be started from this pre-initial charging process from the outer side of the electrode to the inner side (current collector side) regardless of the thickness direction of the electrode. Further, the gas generated during the pre-initial charge is closed by a clip or the like, and after the pre-initial charge, the gas is generated during the pre-initial charge by removing the clip and opening one side of the three-side sealing body 71 Can be easily discharged from the exterior body. In addition, after pre-initial charging in a closed state with a clip or the like, for example, by rolling from the side opposite to the unsealed side of the exterior body, the gas generated inside the battery is unsealed. You may extrude to the edge side (internal space part of the clearance gap between an exterior body and a laminated body). Thereafter, by removing the clip and opening one side of the three-side sealing body 71, the gas generated by the pre-initial charge can be easily and reliably discharged from the exterior body.

[VII] Second impregnation step ("impregnation" step 3e in FIG. 4)
In this step, it is only necessary that the three-side sealed body after the pre-initial charge is allowed to stand for a certain period of time to promote the impregnation with the electrolytic solution, and is not particularly limited, and a conventionally known method can be applied. Usually, by leaving it to stand for 24 hours or more (up to about several days), the electrolytic solution is promoted to impregnate into every corner of the separator and the active material layer. Depending on the case, it may be performed in an environment in which the battery is easily impregnated with the electrolytic solution by repeating the pressurization and depressurization using the vacuum box 87 or the vacuum pump used in the liquid injection process. Also, the atmosphere is preferably performed in a dry environment containing no moisture, for example, in a dry inert gas atmosphere. Moreover, depending on the case, you may make it accelerate | stimulate that an electrolyte solution is impregnated by applying the gentle ultrasonic vibration of the grade which does not destroy an electrode. In addition, by sufficiently impregnating the electrolyte not only outside the electrode but also inside the electrode (current collector side), as described above, from the outside of the electrode to the inside ( It is also excellent in that uniform SEI can be formed up to the current collector side. Also, in the second impregnation step, as shown in FIG. 4, the formation of SEI is progressing, and the formation of SEI is sufficiently advanced not only outside the electrode but also inside the electrode (current collector side). Can do.

[VIII] Initial charging step ("impregnation" step 3f in FIG. 4)
In this step, it is only necessary that the initial charging can be performed at a predetermined charging rate, and there is no particular limitation, and a conventionally known method can be applied. Usually, the charging may be performed at a charging rate of 0.1 C to 2.0 C until the battery is fully charged (usually, the voltage per unit cell layer is 4.2 V). Thereby, as shown in FIG. 4, formation of uniform SEI from the outer side of the electrode to the inner side (current collector side) can be completed irrespective of the thickness direction of the negative electrode. In the present invention, since the SEI can be formed in a short time, the initial charge can be performed in about 3 hours. On the other hand, in the conventional manufacturing method shown in FIGS. 7 to 10, since it is necessary to move the electrolyte (particularly the additive) from the positive electrode side to the negative electrode side during the initial charge, it takes a long time to form SEI. Charging takes about 5.5 hours, nearly twice as long as the present invention. Furthermore, in the conventional manufacturing method, as shown in FIG. 4, the formation of SEI is not completed by only the initial charge, and then high temperature aging for 14 days or more, and further room temperature aging for 14 days or more are necessary. As a result, the formation of SEI was finally completed.

  In this process, a large amount of gas generated during pre-initial charging is closed with a clip or the like, and after the initial charging, the clip is removed and one side of the three-side sealing body 71 is opened to perform initial charging. A large amount of gas generated in can be easily discharged from the exterior body. In addition, after the initial charge in a closed state with a clip or the like, for example, a large amount of gas generated inside the battery is unsealed by rolling the roller from the side opposite to the unsealed side of the exterior body. You may extrude to the edge | side of a stop (internal space part of the clearance gap between an exterior body and a laminated body). Thereafter, by removing the clip and opening one side of the three-side sealing body 71, the gas generated by the initial charge can be easily and reliably discharged from the exterior body. Finally, the three-side sealing body 71 is taken out from the vacuum box 87, and the remaining one side of the three-side sealing body 71 is sealed (heat-sealed) to obtain a laminate type (laminated structure) lithium ion secondary battery. Can be completed.

  In the production method of the present invention, a desired nonaqueous electrolyte secondary battery can be obtained by this step. As shown in FIG. 4, a high-temperature aging step that requires 14 days or more, and further 14 days or more as required. There is no need to perform room temperature aging (not shown), and the battery can be completed in a very short time (in terms of production efficiency and mass production).

  The nonaqueous electrolyte secondary battery (laminated structure battery) of the present embodiment described above has the following effects.

  The method for producing a non-aqueous electrolyte secondary battery according to this embodiment is characterized in that the negative electrode slurry used for forming the negative electrode contains an additive for SEI formation. Preferably, the electrolyte solution and the positive electrode slurry used for positive electrode formation do not contain any additive for SEI formation.

  By having the above configuration, battery performance can be improved by generating high-quality SEI (particularly, a uniform film in the thickness direction of the negative electrode active material layer).

  That is, since the SEI becomes a resistance component, in the manufacturing method of the present embodiment in which the SEI can be uniformly formed regardless of the thickness direction of the negative electrode, a decrease in the capacity of the obtained battery is suppressed and the life is extended. (Refer to FIG. 11 to FIG. 14 and FIG. 7 to FIG. 10 for comparison).

  Furthermore, as shown in FIG. 4, there is no need to perform a high temperature aging process that requires 14 days or more, and further room temperature aging for 14 days or more, and the battery can be completed in a very short time (production efficiency and mass production). ) Excellent in terms.

Example 1
A battery was produced according to the process flow shown in FIG.

[I] Positive electrode forming step (1) Positive electrode slurry preparing step (“Slurry making” step 1a in FIG. 4)
A solid content comprising 92% by mass of LiMn ₂ O ₄ (average particle size: 15 μm) as a positive electrode active material, 4% by mass of acetylene black as a conductive auxiliary agent, and 4% by mass of PVdF as a binder was prepared. A suitable amount of N-methyl-2-pyrrolidone (NMP), which is a slurry viscosity adjusting solvent, is added to the solid content, and the viscosity is adjusted so that the slurry viscosity is in the range of 20000 to 300,000 cps (approximately 10000 cps). A slurry was prepared.

(2) Positive electrode fabric preparation process (“application / drying” process 1b + “press” process 1c in FIG. 4)
An aluminum foil having a thickness of 20 μm was purchased as a roll and used as a positive electrode current collector foil. The positive electrode slurry was continuously applied using a coater onto the current collector that was continuously conveyed while being unwound from the positive electrode current collector foil attached to the unwinding roller. Next, the current collector on which the positive electrode slurry coating film was formed was continuously dried using a drying means using both hot air drying and IR drying to remove the slurry viscosity adjusting solvent contained in the slurry coating film. The drying conditions were in the range of 80 to 130 ° C. The above application and drying are performed on the current collector surface (A surface), and then the other surface (B surface) of the current collector is applied and dried in the same manner on both surfaces of the current collector. A dry coating was formed. Next, the current collector having a dry coating film is roll-pressed and adjusted so that the slurry dry coating film (positive electrode active material layer) has a target density (about 1.0 g / cm ³ ). Got anti. Moreover, the press system used the cold press.

(3) Positive electrode manufacturing step (“slit” step 1d in FIG. 4)
The positive electrode raw material wound up in a roll shape by the winding roller obtained above is attached again to the unwinding roller, and since the positive electrode raw material is not unwound, a slitter (cutting means) is used. A rectangular shape was cut according to the electrode size. Next, the cut positive electrode is dried at 70 ° C. or higher for 7 hours or more by using a vacuum dryer to remove moisture adhered by drying in the positive electrode raw material preparation step (2) above, A positive electrode (thickness 180 ± 10 μm) having a target density, size, and shape was obtained.

[II] Negative electrode formation step (1) Negative electrode slurry preparation step ("slurry preparation" step 2a in FIG. 4)
Artificial graphite (average particle size: 20 μm) 93% by mass as a negative electrode active material, acetylene black 0.5% by mass as a conductive additive, PVdF 5% by mass as a binder, and methylene methane disulfonate 1.5% by mass as an additive for SEI formation % Solid content was prepared. An appropriate amount of N-methyl-2-pyrrolidone (NMP), which is a slurry viscosity adjusting solvent, is added to the solid content, and the viscosity is adjusted so that the slurry viscosity is in the range of 20000 to 300,000 cps (approximately 10000 cps). A slurry was prepared.

(2) Negative electrode raw material production process ("application / drying" process 2b + "press" process 2c in FIG. 4)
A copper foil having a thickness of 10 μm was purchased as a roll and used as a negative electrode current collector foil. A negative electrode slurry was continuously applied using a coater onto a current collector that was continuously conveyed while being unwound from the negative electrode current collector foil attached to an unwinding roller. Next, the current collector on which the negative electrode slurry coating film was formed was continuously dried using a drying means that used both hot air drying and IR drying to remove the slurry viscosity adjusting solvent contained in the slurry coating film. The drying conditions were in the range of 80 to 130 ° C. The above application and drying are performed on the current collector surface (A surface), and then the other surface (B surface) of the current collector is applied and dried in the same manner on both surfaces of the current collector. A dry coating was formed. Next, the current collector having a dry coating film is roll-pressed and adjusted so that the slurry dry coating film (negative electrode active material layer) has a target density (about 1.0 g / cm ³ ). Got anti. Moreover, the press system used the cold press.

(3) Negative electrode manufacturing step (“slit” step 2d in FIG. 4)
The negative electrode raw material wound up in the form of a roll by the winding roller obtained above is attached again to the unwinding roller, and the negative electrode raw material is not unwound, so it is adjusted to the desired electrode size using a slitter. And cut into a rectangular shape. Next, the cut negative electrode is dried at 70 ° C. or higher for 7 hours or more using a vacuum dryer to remove moisture adhered by drying in the negative electrode raw material preparation step of (2) above. A negative electrode (thickness 130 ± 10 μm) having the target density, size, and shape was obtained.

[III] Step of laminating the positive electrode, the negative electrode, and the separator to form a laminate (“lamination / tab welding” step 3a in FIG. 4)
As shown in FIG. 15, 28 positive electrodes and 29 negative electrodes obtained in the above steps [I] and [II] and 56 separators are alternately arranged in the order of positive electrode, separator, negative electrode, separator, positive electrode,. A laminated body having a desired number of stacked layers (16 cells) was formed. Here, the separator is the same as the positive electrode and the negative electrode, and a polypropylene (PP) microporous film (thickness 25 μm) is purchased with a roll as a separator raw material. The separator raw material is used with a slitter. It was cut into a rectangular shape according to the separator size and dried at 70 ° C. or higher for 7 hours or more using a vacuum dryer. Next, as shown in FIG. 15, a positive electrode tab and a negative electrode tab were joined to each current collector of the laminate by an ultrasonic welding machine and trimmed.

[IV] A step of injecting an electrolyte into the laminate (“injection” step 3b in FIG. 4)
First, as shown in FIG. 16, the laminate is a laminate film used for a battery outer package, and a positive electrode current collector plate (positive electrode current collector tab) and a negative electrode current collector plate (negative electrode current collector tab) are formed from the upper and lower sides of the battery outer package. Between the outer peripheral portions (sealing portions) of the upper and lower laminate films, the three sides were sealed by thermocompression bonding so that they could be taken out to the outside. This obtained the 3 side sealing body shown in FIG. Next, an electrolytic solution is injected from the opening on one side where the three-side sealing body remains with the liquid injection device shown in FIG. As a result, an electrolyte layer in which the separator is impregnated with the electrolytic solution is formed.

Here, a mixed solvent (30:30:40 (volume ratio)) of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) was used as the solvent for the electrolytic solution. Further, 1.0M LiPF ₆ was used as a supporting salt. Furthermore, it added so that it might become a total of 100 mass% of the said solvent and the said support salt, and produced electrolyte solution. “1.0 M LiPF ₆ ” means that the concentration of the supporting salt (LiPF ₆ ) in the mixture of the mixed solvent and the supporting salt is 1.0 M.

[V] First impregnation step (“impregnation” step 3c in FIG. 4)
Next, the three-sided sealed body after the injection was allowed to stand for a certain period of time (one hour or more, here 2 hours), and impregnated with the injected electrolyte.

[VI] Pre-initial charging step ("impregnation" step 3d in FIG. 4)
Next, the remaining one side of the three-side sealing body after the first impregnation step was closed with a clip, and then pre-initial charging was performed at a predetermined charging rate (1 hour at a charging rate of 0.1 C). As shown in FIG. 4, formation of uniform SEI can be started from the outer side of the electrode to the inner side (current collector side) regardless of the thickness direction of the electrode from the pre-initial charging step. Further, the gas generated during the pre-initial charge was discharged from the exterior body by removing the clip and opening the remaining one side of the three-side sealing body.

[VII] Second impregnation step ("impregnation" step 3e in FIG. 4)
The three-sided sealed body after the pre-initial charge was allowed to stand for a predetermined time of 24 hours or longer (here, 24 hours) to promote the impregnation of the electrolytic solution.

[VIII] Initial charging step ("impregnation" step 3f in FIG. 4)
In this step, after the remaining one side of the second impregnation step 3 side sealing body is closed with a clip, at a predetermined charging rate (at a charging rate of 1.0 C, fully charged (to a cell layer potential of 4.2 V) As shown in Fig. 4, formation of uniform SEI was completed from the outside of the electrode to the inside (current collector side), regardless of the thickness direction of the negative electrode. In the example, the SEI can be formed in a short time, so that the initial charge can be performed in 3 hours.In addition, a large amount of gas generated during the pre-initial charge is removed from the clip, and one side of the three-side sealed body is removed. Finally, the remaining side of the three-side sealed body was sealed (heat sealed) to complete a laminate type (laminated structure) lithium ion secondary battery. It was.

Comparative Example 1
Lithium ion secondary battery in the same manner as in Example, except that negative electrode slurry not containing SEI formation additive was used, SEI formation additive was added to the electrolyte, and high temperature aging process was performed after the initial charging process. Was completed.

Here, the negative electrode slurry prepared as follows was used.
A solid content comprising 94.5% by mass of artificial graphite (average particle size: 20 μm) as a negative electrode active material, 0.5% by mass of acetylene black as a conductive additive, and 5% by mass of PVdF as a binder was prepared. An appropriate amount of N-methyl-2-pyrrolidone (NMP), which is a slurry viscosity adjusting solvent, is added to the solid content, and the viscosity is adjusted so that the slurry viscosity is in the range of 20000 to 300,000 cps (approximately 10000 cps). A slurry was prepared.

  Moreover, the thing of the following compositions was used for electrolyte solution.

The electrolyte includes a mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) (30:30:40 (volume ratio)) and 1.0M LiPF ₆ as an electrolyte as a supporting salt. Was further added as an additive for SEI formation so as to be 1.6% by mass of methylenemethane disulfonate (MMD) to prepare an electrolytic solution.

  In Comparative Example 1, as shown in FIG. 7 to FIG. 10, it is necessary to move the electrolyte (particularly the additive) from the positive electrode side to the negative electrode side during the initial charge. Charging also took 5.5 hours, nearly twice that of Example 1.

  Furthermore, in Comparative Example 1, as shown in FIG. 4, the formation of SEI was not completed by only the initial charge, and then high temperature aging at 55 ° C. for 20 days and further room temperature aging for 20 days had to be performed. It was. This finally completed the formation of SEI.

  In the production method of the present invention, a desired nonaqueous electrolyte secondary battery can be obtained by this step, and as shown in FIG. 4, there is no need to perform a long-term high-temperature aging step and a normal-temperature aging step, and an extremely short time. I was able to complete the battery.

6). Battery Characteristic Evaluation (1) Content of SEI formation additive (amount of transition from additive to SEI)
In each production step of the battery of Example 1 and Comparative Example 1, the electrolyte solution impregnated in the separator was extracted (the electrolyte solution impregnated on the negative electrode side was extracted as much as possible), and the SEI formation additive was analyzed by combustion ion chromatography. The content (mass) was measured. The obtained results are shown in Table 1 below. Content in Table 1 shows the ratio (mass%) with respect to the whole content (100 mass%) of the sampled electrolyte solution.

  In Example 1, as shown in FIGS. 11, 13, and 14, since SEI derived from the additive is generated from the additive on the surface of the negative electrode active material particles, the dissolution into the electrolytic solution does not occur. No additive was observed in the stage electrolyte. On the other hand, in Comparative Example 1, it was found that the transition from the additive to the SEI derived from the additive was not completed in the electrolytic solution even after the first charge, and the formation of SEI was finally completed by room temperature aging. .

(2) SEM observation In the manufacturing steps of the batteries of Example 1 and Comparative Example 1, after the first charge, the cross sections of the outer side and the inner side (current collector side) in the thickness direction of the negative electrode (active material layer) were SEM (scanning type). The images were taken with an electron microscope and analyzed, and the state of SEI (film) or additives (precipitated particles) on the surface of the active material particles was observed. As a result, in Example 1, uniform SEI (film) was formed on the outer side and the inner side (current collector side) of the negative electrode (active material layer) regardless of the thickness direction, and the additive No precipitated particles that seemed to be observed. From this, it was confirmed that the formation of SEI was completed in a short time by the first charge as described in FIGS. Further, it was confirmed that high-quality (uniform thickness) SEI was formed (outside and inside) regardless of the thickness direction of the negative electrode (active material layer). On the other hand, in Comparative Example 1, as shown in FIGS. 7 to 11, very thick SEI is formed on the outer side of the negative electrode (active material layer), whereas no SEI is formed on the inner side. Even if it was formed, it was confirmed that it was a very thin SEI. Moreover, the additive particle | grains from which the additive was thought to have precipitated instead of the film on the surface of the active material particle were recognized.

9 Viscosity adjusting solvent,
10, 30 Lithium ion secondary battery (stacked structure battery),
11 positive electrode current collector (foil),
12 Anode current collector (foil),
13 positive electrode active material layer,
14 positive electrode active material (particles),
15 negative electrode active material layer,
15 'negative electrode slurry coating (wet state),
16 negative electrode active material (particles),
17 electrolyte layer,
18 SEI forming additive,
18a SEI,
19 cell layer,
20 Li ion,
21, 37 Power generation element,
22 Charger,
25, 38 Positive current collector (positive current collector tab),
27, 39 Negative electrode current collector plate (negative electrode current collector tab),
29, 32 Battery exterior material (laminate film),
31 Separator and electrode surface,
33a Striped adhesive part (stripe),
33b Dot-shaped adhesive part (dot),
35 Non-adhesive part,
51 slurry preparation equipment,
52 Container for slurry preparation device,
53 Container lid of slurry preparation device,
54 stirring means,
55 negative electrode active material (particles),
56 SEI forming additive,
57 negative electrode,
58 High resistance film derived from solvent in electrolyte,
59 SEI derived from SEI forming additive,
61 laminate,
62 positive electrode,
62a positive electrode tab,
62A Positive current collecting tab 63 Negative electrode,
63a Negative electrode tab 63A Negative electrode current collecting tab 64 Separator,
65 Laminated film,
65a exterior body,
66 The outer peripheral part (sealing part) of the laminate film,
66a heat sealing part of the outer package,
67 Insulation reinforcement sheet,
68 Opening on one side where the three-side sealing body remains,
71 3 side sealing body,
81 liquid injection device,
83 Electrolyte transport line,
85 Injection nozzle,
87 Vacuum box.

Claims (4)

At least the negative electrode slurry used for negative electrode formation contains an additive for SEI formation,
The SEI forming additive, Ri cyclic disulfonic acid ester der,
The non-aqueous electrolyte 2 is characterized in that the SEI-forming additive is in the range of 0.5 to 2.0 mass% with respect to the total amount of solid content of the negative electrode slurry (component of the negative electrode active material layer). A method for manufacturing a secondary battery.   The method for producing a nonaqueous electrolyte secondary battery according to claim 1, wherein the positive electrode slurry used for forming the electrolytic solution and the positive electrode does not contain an additive for forming SEI.   The method for producing a nonaqueous electrolyte secondary battery according to claim 1, wherein the SEI forming additive contains a compound that is reductively decomposed at a potential higher than 0.2 V with respect to lithium metal. It is a manufacturing method of Claims 1-3 ,
A positive electrode forming step using a positive electrode slurry containing a positive electrode active material;
A negative electrode forming step using a negative electrode slurry containing a negative electrode active material;
A step of laminating the positive electrode and the negative electrode obtained in the positive electrode forming step and the negative electrode forming step, and a separator to form a laminate;
Injecting an electrolyte solution into the laminate,
A method for producing a non-aqueous electrolyte secondary battery, wherein the negative electrode slurry contains an additive for SEI formation.