JP6907694B2 - Rechargeable battery manufacturing method and rechargeable battery - Google Patents

Description

The present invention relates to a method for manufacturing a secondary battery and a secondary battery. In particular, the present invention relates to a method for manufacturing a secondary battery including an electrode assembly composed of an electrode constituent layer including a positive electrode, a negative electrode and a separator, and also relates to a secondary battery obtained by the manufacturing method.

Since the secondary battery is a so-called storage battery, it can be repeatedly charged and discharged, and is used for various purposes. For example, secondary batteries are used in mobile devices such as mobile phones, smartphones and notebook computers.

The secondary battery is composed of at least a positive electrode, a negative electrode, and a separator between them. The positive electrode is composed of a positive electrode material layer and a positive electrode current collector, and the negative electrode is composed of a negative electrode material layer and a negative electrode current collector. In the electrode assembly of the secondary battery, a plurality of such positive electrodes and negative electrodes are laminated via a separator, and the electrode assembly having this laminated body form is housed in the exterior body.

Special Table 2015-536036 Japanese Patent No. 3801087 Japanese Unexamined Patent Publication No. 2014-12456 Japanese Unexamined Patent Publication No. 2011-228634

The inventor of the present application noticed that there is a problem to be overcome with the conventional secondary battery, and found that it is necessary to take measures for that purpose. Specifically, the inventor of the present application has found that there are the following problems.

The electrode assembly having a two-dimensional laminated structure has a structure in which electrode layers of a positive electrode and a negative electrode are stacked on each other via a separator. The inventor of the present application has found that a warp phenomenon occurs in such an electrode assembly.

Specifically, it has been found that the electrode assembly may be accompanied by a so-called warp phenomenon in which a part of the portion corresponding to the outermost layer is warped during its production (see FIG. 12). This is particularly remarkable when the electrode corresponding to the outermost layer of the electrode assembly is a so-called single-sided electrode. Although it is preferable to use the outermost layer of the electrode assembly as a single-sided electrode in terms of the energy density of the secondary battery, the single-sided electrode itself tends to warp, which makes it difficult to obtain a desired secondary battery.

When a single-sided electrode is used as the outermost layer of the electrode assembly, a double-sided electrode is often used for the assembly other than the outermost layer. A double-sided electrode is an electrode in which electrode material layers are provided on both main surfaces of an electrode current collector (hereinafter, also simply referred to as a "current collector"). Such a double-sided electrode is obtained by applying an electrode material raw material to both main surfaces of a current collector, drying the electrode material, and then subjecting the electrode material to a press treatment to increase the density. On the other hand, the single-sided electrode is an electrode in which an electrode material layer is provided only on one of both main surfaces of the current collector. Such a single-sided electrode is obtained by applying an electrode material raw material to one main surface of a current collector, drying it, and then subjecting it to a press treatment to increase its density.

The current collector is mainly composed of a metal material such as a metal foil, while the electrode material raw material is mainly composed of an electrode active material and a binder. Such a difference in the constituent materials may affect the electrode behavior during the press process. For example, during the press process, stress is generated in the electrode due to differences in the stretching behavior of the current collector and the electrode material layer. Since the double-sided electrodes can cancel each other out on both main surfaces of the current collector, such stress is negligible, while the stress of the single-sided electrode is not negligible, and as a result, the single-sided electrode is warped. There is.

Since it is a single-sided electrode having such a tendency to warp, if it is used as the outermost layer of the electrode assembly, the electrode assembly will be warped, and stacking deviation or the like will occur. Lamination misalignment can lead to a decrease in the energy density of the secondary battery. In order to alleviate the warp, it is conceivable to use a thick metal foil as the current collector of the single-sided electrode or reduce the density of the single-sided electrode itself, but this time the electrode thickness increases and the secondary battery It causes a decrease in the energy density of.

The present invention has been made in view of such a problem. That is, a main object of the present invention is to provide a technique for manufacturing a secondary battery in which the warp phenomenon related to the electrode assembly is reduced.

The inventor of the present application has attempted to solve the above problems by dealing with it in a new direction, rather than dealing with it as an extension of the prior art. As a result, they have invented a technology for manufacturing a secondary battery that has achieved the above-mentioned main purpose.

The present invention is a method for manufacturing a secondary battery including an electrode assembly having a flat laminated structure and an exterior body for accommodating the electrode assembly.
Provided is a method for manufacturing a secondary battery in which an outermost layer electrode used as an outermost layer of an electrode assembly is thermally bonded to an outer body.

The present invention also provides a secondary battery. The secondary battery of the present invention comprises an electrode assembly having a two-dimensional laminated structure and an exterior body for accommodating the electrode assembly.
A thermal joint portion for joining between the outermost layer electrode forming the outermost layer of the electrode assembly and the outer body is provided.

In the present invention, the warpage phenomenon associated with the electrode assembly can be reduced. Therefore, it becomes easy to obtain a desired secondary battery.

In particular, even when a single-sided electrode is used as the outermost layer of the electrode assembly, inconveniences due to warpage of the single-sided electrode can be reduced. More specifically, in the electrode assembly, the stacking deviation caused by the warp is reduced. It also reduces the need to use a thick metal leaf as the electrode current collector to reduce warpage and reduce the density of the electrodes. Therefore, the secondary battery of the present invention is a battery in which the decrease in energy density due to warpage is effectively suppressed or avoided.

Schematic perspective view for explaining the manufacturing method of the present invention (before thermal bonding) Schematic perspective view for explaining the manufacturing method of the present invention (after thermal bonding) Schematic plan view for explaining the outer edge portion Top view of the outermost layer electrodes to illustrate the current collector exposed area Top view of the outermost layer electrode for explaining the thermal junction / thermal junction Top view of the outermost layer electrode for explaining the thermal junction / thermal junction Schematic perspective view for explaining the mode of positively using the adhesive separator. Schematic perspective view and development view for explaining the secondary battery of the present invention. Schematic diagram for exemplifying heat bonding treatment of non-rectangular electrode assembly / outermost layer electrode Schematic diagram for explaining a non-rectangular shape (partially notched shape) Top view of the outermost layer electrode for explaining the arrangement form of a plurality of thermal junctions Schematic diagram for explaining the warp of the outermost layer electrode, which is a subject of the present invention. Schematic cross-sectional view for explaining an electrode assembly having a two-dimensional laminated structure.

Hereinafter, the "method for manufacturing a secondary battery" and the "secondary battery" according to the embodiment of the present invention will be described in more detail. Although explanations will be given with reference to the drawings as necessary, the various elements in the drawings are merely schematically and exemplified for the understanding of the present invention, and the appearance, dimensional ratio, etc. may differ from the actual ones. ..

The "plan view (or plan view shape)" described directly or indirectly in the present specification is the stacking direction of the electrode material layers constituting the secondary battery (thickness direction of the battery, the electrode assembly, or the electrode material layer). ) Is based on the form when the object is grasped from the outside. Further, the “cross-sectional view (or cross-sectional view shape)” described directly or indirectly in the present specification is in the stacking direction of the electrode material layers constituting the secondary battery (thickness direction of the battery or the electrode material layer). It is based on a hypothetical cross section of the rechargeable battery cut out along.

Further, the "vertical direction" and the "horizontal direction" used directly or indirectly in the present specification correspond to the vertical direction and the horizontal direction in the drawings, respectively. Unless otherwise specified, the same code or symbol shall indicate the same member or the same meaning.

[Structure of a secondary battery manufactured by the present invention]
A secondary battery can be obtained by the manufacturing method of the present invention. The term "secondary battery" as used herein refers to a battery that can be repeatedly charged and discharged. Therefore, the secondary battery obtained by the manufacturing method of the present invention is not excessively bound by its name, and for example, a power storage device and the like can be included in the subject.

The secondary battery according to the present invention includes an electrode assembly in which electrode constituent layers including a positive electrode, a negative electrode, and a separator are laminated. FIG. 13 schematically illustrates an electrode assembly. As shown in the drawing, the positive electrode 1 and the negative electrode 2 are stacked with each other via the separator 3 to form an electrode constituent layer 10, and at least one or more of the electrode constituent layers 10 are laminated to form an electrode assembly. There is. In a secondary battery, such an electrode assembly is enclosed in an exterior body together with an electrolyte (for example, a non-aqueous electrolyte).

The positive electrode is composed of at least a positive electrode material layer and a positive electrode current collector. In the positive electrode, a positive electrode material layer is provided on at least one surface of the positive electrode current collector, and the positive electrode material layer contains a positive electrode active material as an electrode active material. For example, each of the plurality of positive electrodes in the electrode assembly may be provided with positive electrode material layers on both sides of the positive electrode current collector, or may be provided with positive electrode material layers on only one side of the positive electrode current collector. .. From the viewpoint of further increasing the capacity of the secondary battery, it is preferable that the positive electrode is provided with positive electrode material layers on both sides of the positive electrode current collector.

The negative electrode is composed of at least a negative electrode material layer and a negative electrode current collector. In the negative electrode, a negative electrode material layer is provided on at least one surface of the negative electrode current collector, and the negative electrode material layer contains a negative electrode active material as an electrode active material. For example, each of the plurality of negative electrodes in the electrode assembly may be provided with a negative electrode material layer on both sides of the negative electrode current collector, or may be provided with a negative electrode material layer on only one side of the negative electrode current collector. .. From the viewpoint of further increasing the capacity of the secondary battery, it is preferable that the negative electrode is provided with negative electrode material layers on both sides of the negative electrode current collector.

The electrode active materials contained in the positive electrode and the negative electrode, that is, the positive electrode active material and the negative electrode active material are substances that are directly involved in the transfer of electrons in the secondary battery, and are the main substances of the positive and negative electrodes that are responsible for charge / discharge, that is, the battery reaction. be. More specifically, ions are brought to the electrolyte due to the "positive electrode active material contained in the positive electrode material layer" and the "negative electrode active material contained in the negative electrode material layer", and such ions are transferred between the positive electrode and the negative electrode. The electrons are transferred and charged / discharged. The positive electrode material layer and the negative electrode material layer are particularly preferably layers capable of occluding and releasing lithium ions. That is, it is preferable that the non-aqueous electrolyte secondary battery is a non-aqueous electrolyte secondary battery in which lithium ions move between the positive electrode and the negative electrode via the non-aqueous electrolyte to charge and discharge the battery. When lithium ions are involved in charging / discharging, the secondary battery obtained by the production method of the present invention corresponds to a so-called lithium ion battery, and the positive electrode and the negative electrode have layers capable of occluding and discharging lithium ions.

When the positive electrode active material of the positive electrode material layer is composed of, for example, granules, it is preferable that the positive electrode material layer contains a binder (also referred to as a binder) for sufficient contact between particles and shape retention. Further, a conductive auxiliary agent may be contained in the positive electrode material layer in order to facilitate the transfer of electrons that promote the battery reaction. Similarly, when the negative electrode active material of the negative electrode material layer is composed of particles, for example, it is preferable that the negative electrode active material contains a binder for sufficient contact between particles and shape retention, and facilitates the transfer of electrons that promote the battery reaction. A conductive auxiliary agent may be contained in the negative electrode material layer. As described above, since the form is composed of a plurality of components, the positive electrode material layer and the negative electrode material layer can also be referred to as a positive electrode mixture layer and a negative electrode mixture layer, respectively.

The positive electrode active material is preferably a substance that contributes to the occlusion and release of lithium ions. From this point of view, the positive electrode active material is preferably, for example, a lithium-containing composite oxide. More specifically, the positive electrode active material is preferably a lithium transition metal composite oxide containing lithium and at least one transition metal selected from the group consisting of cobalt, nickel, manganese and iron. That is, such a lithium transition metal composite oxide is preferably contained as a positive electrode active material in the positive electrode material layer of the secondary battery obtained by the production method of the present invention. For example, the positive electrode active material may be lithium cobalt oxide, lithium nickel oxide, lithium manganate, lithium iron phosphate, or a part of the transition metal thereof replaced with another metal. Such a positive electrode active material may be contained as a single species, but may be contained in combination of two or more species. Although it is merely an example, in the secondary battery obtained by the production method of the present invention, the positive electrode active material contained in the positive electrode material layer may be lithium cobalt oxide.

The binder that can be contained in the positive electrode material layer is not particularly limited, but is limited to, but is not limited to, a polyvinylidene fluoride, a vinylidene fluoride-hexafluoropropylene copolymer, a bilinidene fluoride-tetrafluoroethylene copolymer, and the like. At least one selected from the group consisting of polytetrafluoroethylene and the like can be mentioned. The conductive auxiliary agent that can be contained in the positive electrode material layer is not particularly limited, but is limited to carbon black such as thermal black, furnace black, channel black, ketjen black and acetylene black, graphite, carbon nanotubes, and vapor phase growth. At least one selected from carbon fibers such as carbon fibers, metal powders such as copper, nickel, aluminum and silver, and polyphenylene derivatives can be mentioned. For example, the binder of the positive electrode material layer may be polyvinylidene fluoride, and the conductive auxiliary agent of the positive electrode material layer may be carbon black. Although only an example, the binder and the conductive auxiliary agent of the positive electrode material layer may be a combination of polyvinylidene fluoride and carbon black.

The negative electrode active material is preferably a substance that contributes to the occlusion and release of lithium ions. From this point of view, the negative electrode active material is preferably, for example, various carbon materials, oxides, lithium alloys, or the like.

Examples of various carbon materials for the negative electrode active material include graphite (natural graphite, artificial graphite), hard carbon, soft carbon, and diamond-like carbon. In particular, graphite is preferable because it has high electron conductivity and excellent adhesion to a negative electrode current collector. Examples of the oxide of the negative electrode active material include at least one selected from the group consisting of silicon oxide, tin oxide, indium oxide, zinc oxide, lithium oxide and the like. The lithium alloy of the negative electrode active material may be any metal that can be alloyed with lithium, for example, Al, Si, Pb, Sn, In, Bi, Ag, Ba, Ca, Hg, Pd, Pt, Te, Zn, It may be a binary, ternary or higher alloy of a metal such as La and lithium. It is preferable that such an oxide is amorphous as its structural form. This is because deterioration due to non-uniformity such as grain boundaries or defects is less likely to occur. Although it is merely an example, in the secondary battery obtained by the production method of the present invention, the negative electrode active material of the negative electrode material layer may be artificial graphite.

The binder that can be contained in the negative electrode material layer is not particularly limited, but is at least one selected from the group consisting of styrene-butadiene rubber, polyacrylic acid, polyvinylidene fluoride, polyimide-based resin, and polyamide-imide-based resin. Can be mentioned. For example, the binder contained in the negative electrode material layer may be styrene-butadiene rubber. The conductive auxiliary agent that can be contained in the negative electrode material layer is not particularly limited, but is limited to carbon black such as thermal black, furnace black, channel black, ketjen black and acetylene black, graphite, carbon nanotubes, and vapor phase growth. At least one selected from carbon fibers such as carbon fibers, metal powders such as copper, nickel, aluminum and silver, and polyphenylene derivatives can be mentioned. The negative electrode material layer may contain a component derived from a thickener component (for example, carboxylmethyl cellulose) used at the time of manufacturing the battery.

Although only an example, the negative electrode active material and the binder in the negative electrode material layer may be a combination of artificial graphite and styrene-butadiene rubber.

The positive electrode current collector and the negative electrode current collector used for the positive electrode and the negative electrode are members that contribute to collecting and supplying electrons generated by the active material due to the battery reaction. Such a current collector may be a sheet-shaped metal member and may have a perforated or perforated form. For example, the current collector may be a metal leaf, a punching metal, a net, an expanded metal, or the like. The positive electrode current collector used for the positive electrode is preferably made of a metal foil containing at least one selected from the group consisting of aluminum, stainless steel, nickel and the like, and may be, for example, an aluminum foil. On the other hand, the negative electrode current collector used for the negative electrode is preferably one made of a metal foil containing at least one selected from the group consisting of copper, stainless steel, nickel and the like, and may be, for example, a copper foil.

The separator used for the positive electrode and the negative electrode is a member provided from the viewpoint of preventing a short circuit due to contact between the positive and negative electrodes and retaining an electrolyte. In other words, it can be said that the separator is a member through which ions pass while preventing electronic contact between the positive electrode and the negative electrode. Preferably, the separator is a porous or microporous insulating member and has a film morphology due to its small thickness. Although only an example, a microporous polyolefin membrane may be used as the separator. In this regard, the microporous membrane used as the separator may contain, for example, only polyethylene (PE) or polypropylene (PP) as the polyolefin. Furthermore, the separator may be a laminate composed of a "microporous membrane made of PE" and a "microporous membrane made of PP". The surface of the separator may be covered with an inorganic particle coat layer, an adhesive layer, or the like. The surface of the separator may have adhesiveness. In the present invention, the separator should not be particularly bound by its name, and may be a solid electrolyte, a gel-like electrolyte, an insulating inorganic particle, or the like having the same function.

In the secondary battery obtained by the manufacturing method of the present invention, an electrode assembly composed of an electrode constituent layer including a positive electrode, a negative electrode and a separator is enclosed in an exterior together with an electrolyte. When the positive electrode and the negative electrode have a layer capable of occluding and releasing lithium ions, the electrolyte is preferably a "non-aqueous" electrolyte such as an organic electrolyte or an organic solvent (that is, the electrolyte is a non-aqueous electrolyte). preferable). In the electrolyte, metal ions emitted from the electrodes (positive electrode / negative electrode) are present, and therefore, the electrolyte assists the movement of the metal ions in the battery reaction.

A non-aqueous electrolyte is an electrolyte containing a solvent and a solute. As a specific solvent for the non-aqueous electrolyte, one containing at least carbonate is preferable. Such carbonates may be cyclic carbonates and / or chain carbonates. Although not particularly limited, the cyclic carbonates include at least one selected from the group consisting of propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC) and vinylene carbonate (VC). be able to. Examples of the chain carbonates include at least one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC) and dipropyl carbonate (DPC). Although only an example, a combination of cyclic carbonates and chain carbonates may be used as the non-aqueous electrolyte, and for example, a mixture of ethylene carbonate and diethyl carbonate is used. Further, as a specific non-aqueous electrolyte solute, for example, a Li salt such as _{LiPF 6} and / or LiBF _{4 is preferably used.}

The exterior body of the secondary battery encloses the electrode assembly in which the electrode constituent layers including the positive electrode, the negative electrode, and the separator are laminated, but may be in the form of a hard case or even in the form of a soft case. good. Specifically, the exterior body may be a hard case type corresponding to a so-called metal can, or a soft case type corresponding to a pouch made of a so-called laminated film.

[Characteristics of the manufacturing method of the present invention]
The manufacturing method of the present invention is characterized in the manufacturing process of the electrode assembly. In particular, the present invention has an idea that an electrode assembly having a planar laminated structure is divided into an "outermost layer electrode" and another "partial electrode assembly", and the outermost layer electrode is subjected to a thermal bonding treatment. There is.

In the manufacturing method of the present invention, the outermost layer electrode used as the outermost layer of the electrode assembly is heat-bonded to the outer body. That is, prior to completing the electrode assembly, the "electrode which is the outermost layer of the electrode assembly" is heat-bonded to the exterior body for accommodating the electrode assembly.

The term "thermal bonding" as used in the present invention means that the connection process is performed by heat in a broad sense, and in a narrow sense, the outermost layer electrode and the exterior body are connected to each other through a heat action provided from the outside. Means.

As shown in FIGS. 1 and 2, the secondary battery 300 is obtained by housing the electrode assembly 100 in the exterior body 200. The outermost layer electrode 100A is an electrode located on the outermost side of the electrodes constituting the electrode assembly 100. In the present invention, the outermost layer electrode 100A is thermally bonded to the outer body 200 (FIGS. 1 and FIG. 2).

As can be seen from the illustrated embodiment, the term "outermost layer electrode" as used herein refers to the outermost electrode that constitutes the electrode assembly of the secondary battery. That is, in the electrode assembly in which the electrode constituent layers including the positive electrode, the negative electrode and the separator are laminated, the electrode that constitutes the surface layer (outer main surface) corresponds to the outermost layer electrode. Since the outermost layer electrode is an electrode of a secondary battery, it substantially corresponds to either a positive electrode or a negative electrode.

In the manufacturing method of the present invention, the outermost layer electrode 100A in the previous stage constituting the electrode assembly 100 is subjected to thermal bonding. In particular, the outermost layer electrode 100A used as a component of the electrode assembly 100 is heat-bonded to the exterior body 200 in which the electrode assembly 100 is to be accommodated. By such thermal bonding, the outermost layer electrode 100A is fixed to the exterior body 200, and the warp of the outermost layer electrode 100A is reduced. In other words, in the manufacturing method of the present invention, the outermost layer electrode 100A and the exterior body 200 are fixed or integrated with each other through a thermal bonding treatment so that a state in which the warp of the outermost layer electrode 100A is reduced can be obtained.

After being heat-bonded to the exterior body 200, the outermost layer electrode 100A is combined with "an electrode that will form a layer other than the outermost layer". That is, the outermost layer electrode 100A heat-bonded to the exterior body 200 is combined with the "electrodes constituting other than the outermost layer" to form the electrode assembly 100. This means that the "partial electrode assembly 100B corresponding to the portion other than the outermost layer of the electrode assembly" and the "outermost layer electrode 100A thermally bonded to the exterior body" are combined with each other to obtain the electrode assembly 100. Means (see FIGS. 1 and 2). The "partial electrode assembly" referred to in the present specification is a stage before the outermost layer electrode is provided and the electrode assembly (finished product) is finally obtained, and corresponds to a precursor of the electrode assembly. do. Although it is merely an example, the electrodes (positive electrode and negative electrode) included in the partial electrode assembly are preferably double-sided electrodes, that is, electrodes in which electrode material layers are provided on both main surfaces of the electrode current collector.

The electrode assembly 100 obtained by the manufacturing method of the present invention is positioned inside the exterior body 200 to the last. Prior to completing the electrode assembly, the outermost layer electrode 100A is preliminarily fixed to the inner surface of the exterior body 200. That is, in the manufacturing method of the present invention, the outermost layer electrode 100A is thermally bonded to the inner surface of the exterior body 200. In particular, it is preferable that the outermost layer electrode 100A is heat-bonded to the inner main surface of the outer body 200 that forms the main surface of the outer body. This means that after the outermost layer electrodes and the exterior body are superposed on each other, the heat bonding treatment is preferably performed from the inside of the exterior body (not the heat bonding treatment from the outside of the exterior body).

In the manufacturing method of the present invention, the outermost layer electrode 100A heat-bonded to the exterior body is integrated with the exterior body due to the heat bonding, and the warp is reduced. That is, even if the outermost layer electrode 100A is warped before joining, the warp is corrected due to the integration with the exterior body by thermal joining. Further, even if the outermost layer electrode 100 integrated with the exterior body is subjected to external fluctuations such as a further press treatment (for example, a press treatment for the entire electrode assembly) later, the presence of the thermal junction portion is present. Prevents warping. Therefore, it can be said that the outermost layer electrode 100A thermally bonded in the present invention has reduced or avoided warpage.

Since the outermost layer electrode 100A has reduced / avoided warpage, the electrode assembly obtained from the outermost electrode assembly also has reduced / avoided warpage in the same manner. For example, in the electrode assembly, stacking deviation due to warpage is prevented, so that a secondary battery in which a decrease in energy density or the like is suppressed or avoided can be obtained as a result. In addition, no additional measures are required to eliminate the warp of the outermost layer electrode. For example, the need to use a thick metal leaf as the electrode current collector or reduce the density of the electrodes for warpage mitigation is reduced. Therefore, even from this point of view, it is possible to suppress or avoid a decrease in energy density due to warpage.

The thermal bonding performed by the manufacturing method of the present invention is only for the purpose of preventing warpage. The outermost layer electrode is preferably a single-sided electrode in that the warp prevention effect is particularly exhibited. That is, as the outermost layer electrode, it is preferable to use an electrode in which the electrode material layer is provided only on one main surface of the current collector. Therefore, the electrode obtained by applying the electrode material raw material to one main surface of the current collector, drying it, and then pressing it is used as the outermost layer electrode, and the electrode is heat-bonded to the exterior body. In the case of a single-sided electrode, it is preferable that the single-sided electrode and the exterior body are superposed on each other so that the current collector of the electrode is in direct contact with the exterior body, and the heat bonding treatment is performed from the inside of the exterior body. When the outermost layer electrode is a single-sided electrode, the energy density per unit volume of the battery can be improved as compared with the case where the outermost layer electrode is a double-sided electrode. This is because, when the outermost layer electrode is a double-sided electrode, the outermost electrode material layer (the electrode material layer on the side that does not directly face the inner electrode) cannot substantially effectively contribute to the formation of battery capacity. be. That is, by using a single-sided electrode, it is possible to reduce the volume of a portion that cannot contribute to its effectiveness.

In one preferred embodiment, the outer edge of the outermost layer electrode is thermally bonded. That is, as shown in FIG. 2, the peripheral region of the outermost layer electrode 110A is subjected to thermal bonding, and the outermost layer electrode and the exterior body are integrated with each other. When the outermost layer electrode is warped, the warp displacement is generally large at the peripheral portion of the electrode (see FIG. 12). Therefore, in the thermal bonding of the outer edge portion, the portion having a large warp displacement can be fixed to the exterior body, and the warp of the outermost layer electrode can be corrected more effectively.

The "outer edge portion" as used herein refers to an electrode peripheral region in a plan view along the stacking direction of the outermost layer electrodes. As shown in FIG. 3, it refers to a local region slightly extending from the outermost edge of the outermost layer electrode to the inside thereof in a plan view. Although it is merely an example, it is 1% or more and 35% or less, preferably 1% or more and 25% or less of the electrode width dimension from the outermost edge side of the outermost layer electrode (the electrode width dimension along the vertical direction from the outermost edge side). The local region up to the inside corresponds to the outer edge portion by the amount corresponding to% or less, more preferably 1% or more and 15% or less (for example, 1% or more and 10% or less or 1% or more and 5% or less).

In the present invention, it is preferable that the outermost layer electrode 110A is thermally bonded to the current collector exposed region 118 in which the electrode material 115 is not provided (see FIGS. 4 and 5). In FIG. 5, the heat-bonded product formed by the heat-bonding treatment is indicated by “350”. The electrode is obtained by applying and drying the electrode material raw material on the main surface of the current collector, and heat-bonding the uncoated region of the electrode material raw material to integrate the uncoated region with the exterior body. Is preferable. In the case of thermal bonding to the exposed region of the current collector, the electrode material layer of the outermost layer electrode is not attached to the thermal bonding, and the current collector of the outermost layer electrode is attached to the thermal bonding, so that the electrode material layer (positive electrode material layer) is attached. Alternatively, the adverse thermal effect on the negative electrode material layer) can be reduced. In particular, it is more preferable to perform thermal bonding to the current collector exposed region 118 located at the outer edge portion of the outermost layer electrode 110A (see FIGS. 4 and 5). In such a case, the "outer edge portion of the outermost layer electrode" to be thermally bonded corresponds to the exposed region of the current collector. In one preferred embodiment, the outermost layer electrode is larger in plan view size than the partial electrode assembly, and the larger portion is subjected to thermal bonding. More specifically, when compared with the partial electrode assembly (particularly each electrode constituting the electrode material), the coated area of the electrode material material has the same planological size, but the uncoated area of the electrode material material (particularly, the uncoated area of the electrode material material). In particular, the outermost layer electrode having a larger plan view size (the uncoated region of the outer edge portion of the electrode) may be used, and the uncoated region contributing to such an increase in size may be subjected to thermal bonding. Regarding the electrode assembly provided inside the exterior, preferably, the partial electrode assembly 110B is provided with a tab, while the outermost layer electrode 110A is not provided with a tab (see FIG. 1). Therefore, a space due to the tab can be provided inside the exterior body in which the tab of the partial electrode assembly is positioned, and the space portion is attached to a region (that is, heat-bonded) that contributes to the increase in the size of the outermost layer electrode. The outer edge portion) may be positioned.

Among the outer edge portions of the outermost layer electrode, it is preferable to heat-bond the corner portions of the outermost layer electrode. That is, as shown in FIGS. 6 (a) to 6 (d), in a plan view along the stacking direction of the outermost layer electrodes 110A, the region near the contour corner 119 of the outermost layer electrodes 110A is thermally bonded to the outermost layer electrode 110A. The outer layer electrode and the outer body may be integrated with each other. As a result, the portion where the warp displacement is particularly large can be fixed to the exterior body, and the warp of the outermost layer electrode to be thermally bonded to the exterior body can be corrected more effectively. More preferably, heat bonding is performed on the corner region of the outermost layer electrode, which is the exposed region of the current collector. This is because the outermost layer electrode can be integrated with the exterior body and the warp can be corrected without adversely affecting the electrode material.

In the production method of the present invention, thermal bonding may be locally applied in a punctate or linear manner. That is, as shown in FIGS. 5 (a) to 5 (d) and FIGS. 6 (a) to 6 (d), the outermost layer electrode 110A is not subjected to thermal bonding entirely or extensively, but is partially and narrowly heated. The thermal joint portion 350 may be formed by being attached to the joint. In the case of "dotted", as shown in FIGS. 5 (a) to 5 (c) and 6 (a) to 6 (c), spot thermal bonding is performed so that a narrow joint portion 350 is formed. Is preferable. In the case of "linear", as shown in FIGS. 5 (d) and 6 (d), it is preferable to perform continuous thermal bonding so that an elongated joint portion 350 is formed. The elongated joint portion is not limited to a straight line in a plan view, but may have a curved shape or a meandering shape periodically. Either "dotted" or "linear" thermal junctions may be performed discretely or intermittently, thereby forming at least two thermal junctions. The embodiments shown in FIGS. 5 (a) to 5 (d) and FIGS. 6 (a) to 6 (d) relate to the outer edge portion of the outermost layer electrode (particularly, the current collector exposed region located at the outer edge portion). Corresponds to an aspect in which dotted or linear thermal bonding is performed.

Such punctate or linear thermal bonding may be performed "symmetrically". More specifically, as shown in FIGS. 5A to 5D and FIGS. 6A to 6D, the thermal bonding is performed so that at least two thermal bonding portions 350 have a symmetrical positional relationship. You may go. As used herein, the term "having a symmetrical positional relationship" means that at least two thermal junctions have a point-symmetrical or line-symmetrical relationship with each other in a plan view along the stacking direction of the outermost layer electrodes. is doing. Not all thermal junctions need to be symmetrical, and at least two or more of them (for example, even numbers such as 4, 6, 8, 10) have a symmetrical positional or arrangement relationship with each other. I just need to be there. However, it goes without saying that even if it is not symmetrical, it has a certain effect even if it is not at the four corners.

The thermal bonding carried out by the production method of the present invention is not particularly limited as long as it is subjected to a thermal connection process. For example, as thermal welding, at least one selected from the group consisting of arc welding, high energy beam welding, resistance welding, electroslag welding, gas welding, thermit welding and ultrasonic welding may be performed. The arc welding includes coated arc welding, TIG welding, gas shielded arc welding, submerged arc welding, self-shielded arc welding, stud welding, electrogas welding and the like. High energy beam welding also includes electron beam welding and laser welding.

In one preferred embodiment, high energy beam welding is performed as a thermal junction. The high energy beam may be an electron beam or a laser beam. The electron beam or laser beam can be easily focused and more suitable thermal bonding can be performed. Electron beam welding (EBW) can perform welding as a high-speed electron flow that focuses the electrons emitted from an electron gun. On the other hand, in the laser welding method (LBW: Laser Beam Welding), welding can be performed by irradiating a laser beam / laser beam by condensing it with a lens or a mirror.

From the viewpoint of having a higher output density and performing local thermal bonding, it is preferable to perform laser welding as the thermal bonding. That is, it can be said that in laser welding, it is easy to locally (for example, in a dot or linear shape) heat bonding treatment. Although it is merely an example, laser welding using a galvanometer mirror may be performed as the laser welding. In such laser welding, it is possible to perform a thermal bonding process at a high speed and at a flexible point by utilizing reflection by a galvanometer mirror capable of scanning a laser beam / laser beam with high accuracy.

The present invention can be embodied in various aspects. It will be described in detail below.

(Aspect of outermost negative electrode)
In such a mode, the outermost layer electrode serves as a negative electrode. That is, a negative electrode is used as an electrode to be thermally bonded to the exterior body. The negative electrode is preferably a single-sided electrode, and therefore it is preferable to use an electrode having an electrode material layer provided only on one main surface of the current collector. It is preferable to heat-bond the single-sided electrode obtained by applying a negative electrode electrode material (raw material containing a negative electrode active material) to one main surface of the negative electrode current collector, drying the negative electrode, and then pressing the electrode to the exterior body.

In the negative electrode, for example, a copper foil (that is, a copper material) is often used as a current collector. On the other hand, in the case of the hard case type exterior body described later, stainless steel (SUS steel) is often used as the material of the exterior body. In such a material, the melting points of both are relatively close to each other (more specifically, the melting points of both are closer to each other than the relationship between the aluminum material of the positive electrode current collector and the stainless steel material of the exterior body). The processing time for joining can be shortened. That is, it becomes easy to avoid excessive heat input to the electrode assembly and the exterior body, and a more preferable secondary battery can be obtained in terms of heat history. In addition, since the copper foil as the negative electrode current collector has a higher thermal conductivity in the first place (more specifically, because it is higher than the aluminum foil of the positive electrode current collector), the heat bonding processing time is also longer in that respect. Can be shortened.

When a negative electrode of a single-sided electrode is used as the outermost layer electrode, it is preferable that the single-sided electrode and the exterior body are overlapped with each other so that the negative electrode current collector is in direct contact with the exterior body, and heat bonding treatment is performed from the inside of the exterior body. .. In this case, the exterior body and the outermost layer electrode have the same polarity (that is, the negative electrode). It is preferable that the polarity itself is insulated from the positive electrode of the positive electrode tab of the electrode assembly by using an appropriate gasket or the like in the final secondary battery.

When a negative electrode is used as the outermost electrode, the size of the negative electrode material layer (particularly the plan view size) is preferably larger than the size of the positive electrode material layer of the opposite positive electrode. This is because it is possible to more preferably prevent so-called dentite when the secondary battery is used, that is, prevent Li precipitation.

(Aspect of metal can)
In such a mode, the exterior body is a so-called metal can. That is, it is an embodiment in which a hard case type exterior body is used as the exterior body.

The term "hard case type exterior body" in the present specification is used in comparison with a soft case type exterior body (flexible case such as a pouch made of a laminated film), and is made of a rigid body material such as a "can". It refers to the exterior body that consists of. For example, the hard case type exterior body may be a rigid exterior body made of stainless steel (SUS steel), aluminum, or the like.

Typically, the hard case type exterior body 200 is composed of a box-shaped main body portion 250 and a lid portion 270 (see FIGS. 1 and 2). In such a case, the outermost layer electrode 110A is heat-bonded to at least one of the main body 250 and the lid 270 of the exterior body 200. Preferably, the outermost layer electrode 110A is heat-bonded to both the main body portion 250 and the lid portion 270.

In the case of the hard case type, since the exterior body is composed of a material exhibiting particularly thermal conductivity such as stainless steel (SUS steel) or aluminum, a suitable thermal bonding treatment can be easily realized. Further, the rigidity of the hard case is preferable in terms of fixing or integrating the outermost layer electrode with the exterior body, and therefore contributes to more effective warp correction of the outermost layer electrode.

(Aspect of adhesive separator)
Such an embodiment is an embodiment in which an adhesive separator is actively used. Specifically, the "partial electrode assembly 110B corresponding to the portion other than the outermost layer of the electrode assembly" and the "outermost layer electrode 110A thermally bonded to the exterior body 200" are combined with each other to obtain an electrode assembly. At this time, the adhesive separator 150 is interposed between the outermost layer electrode 110A and the partial electrode assembly 110B (see FIG. 7).

By interposing the adhesive separator 150, the outermost layer electrode 110A and the partial electrode assembly 110B can be suitably bonded to each other. Therefore, the integrity of the electrode assembly composed of the outermost layer electrode and the partial electrode assembly is improved (for example, layer misalignment during press processing of the electrode assembly is prevented), and a desired secondary battery can be obtained. It will be easier to obtain.

As the adhesive separator, for example, a microporous membrane made of polyolefin such as polyethylene (PE) or polypropylene (PP) provided with an adhesive layer may be used. The adhesive itself forming the adhesive layer may be that used for conventional secondary batteries. Although only an example, the adhesive layer has insulating properties and may include, for example, polyvinylidene fluoride (PVDF) and / or an acrylic resin (alumina, if necessary). Inorganic fillers such as may be added).

[Secondary battery of the present invention]
The secondary battery of the present invention is obtained by the above-mentioned manufacturing method. Therefore, the secondary battery according to one aspect of the present invention includes an electrode assembly having a planar laminated structure and an exterior body for accommodating the electrode assembly. In particular, the secondary battery 300 of the present invention is provided with a thermal bonding portion 350 for bonding the outermost layer electrode 110A forming the outermost layer of the electrode assembly and the exterior body 200 to each other (see FIG. 8). In other words, where the electrode assembly 100 is provided inside the exterior body 200, the outermost layer electrode 110A of the electrode assembly 100 and the exterior body 200 are fixed or integrated with each other.

The secondary battery of the present invention is provided with a thermal junction for joining the outermost layer electrode and the exterior body to each other, and the warp associated with the electrode assembly is reduced or corrected. .. More specifically, the outermost layer electrode of the electrode assembly is in a state where the warp is reduced or corrected. It can be said that the outermost layer electrode 100A, which is heat-bonded to the exterior body according to the present invention, is an electrode whose warpage is reduced or avoided.

Since the electrode assembly has reduced or corrected warpage, the secondary battery of the present invention is a battery in which stacking misalignment and the like are prevented, and a decrease in energy density and the like is suppressed. In addition, a thick metal foil is not used as the electrode current collector to alleviate the warp, and the density of the electrodes is not lowered. In this respect as well, the battery suppresses the decrease in energy density due to the warp. ..

In one preferred embodiment, a thermal junction is provided at the outer edge of the outermost layer electrode. That is, in the secondary battery of the present invention, the exterior body and the outermost layer electrode of the electrode assembly are preferably integrated in the peripheral region of the outermost layer electrode. Since the electrode assembly is in a state in which the warp is more preferably reduced or corrected, the secondary battery of the present invention is a battery in which the decrease in energy density is more effectively suppressed.

In the outermost layer electrode, it is preferable that the thermal junction is positioned with respect to the exposed region of the current collector in which the electrode material is not provided. That is, in the secondary battery of the present invention, the outermost layer electrode and the outer body are formed not through the electrode material layer of the outermost layer electrode but through the thermal junction formed in the current collector of the outermost layer electrode. Is preferably integrated. In such a case, the "outer edge portion of the outermost layer electrode" where the thermal junction is positioned corresponds to the current collector exposed region.

In one preferred embodiment, among the outer edge portions of the outermost layer electrode, for example, the thermal junction portion is positioned at the corner portion of the outermost layer electrode. That is, in a plan view along the stacking direction of the outermost layer electrodes, the outermost layer electrodes and the exterior body may be integrated with each other via a thermal junction located in a region near the contour corner of the outermost layer electrodes. .. This is because the portion where the warp displacement is considered to be particularly large is fixed to the exterior body, so that the electrode assembly has more preferably reduced or corrected warpage.

In the secondary battery of the present invention, it is preferable that the thermal junction forms a point-like or linear local junction. That is, it is preferable that the outermost layer electrode and the exterior body are integrated with each other via a thermal junction provided in a partial and narrow region of the outermost layer electrode, rather than the whole or a wide range of the outermost layer electrode. In the case of "dotted", the thermal junction preferably has a plan view shape as narrow as possible. On the other hand, in the case of "linear", it is preferable that the thermal junction has an elongated continuous plan view shape (not limited to a linear shape, but a curved shape or a periodic meandering shape). May be).

The number of thermal joints is not limited to one, and at least two may be provided. The at least two thermal junctions may have a symmetrical positional relationship in the plan view of the outermost layer electrode. An electrode assembly with such a "symmetrical" thermal junction can be more preferably warped or straightened. For example, the point-shaped or linear thermal junctions may have a symmetrical positional relationship or arrangement relationship.

In one preferred embodiment, the outermost layer electrode is a single-sided electrode in which an electrode material layer is provided only on one main surface of the current collector. That is, the "electrode obtained by applying the electrode material raw material to one main surface of the current collector, drying it, and then pressing it" is provided as the outermost layer electrode of the electrode assembly. Whereas a single-sided electrode is an electrode that is usually prone to warpage, in the secondary battery of the present invention, the single-sided electrode is integrated with the exterior body via a thermal junction and is fixed. Therefore, even if the electrode assembly includes a single-sided electrode that is generally considered to have a particularly large warp displacement, the electrode assembly is in a state in which the warp is reduced or corrected.

In the case of a single-sided electrode, it is preferable that the single-sided electrode and the outer body are integrated via a thermal junction so that the current collector is in direct contact with the outer body (particularly, the inner surface of the outer body). For example, when the single-sided electrode is a negative electrode, the negative electrode and the exterior body are in direct contact with each other, so that the exterior body and the outermost layer electrode can exhibit the same polarity, that is, the “negative electrode”. The polarity of the negative electrode itself is preferably insulated from the "positive electrode" of the positive electrode tab of the electrode assembly by an appropriate gasket or the like.

In one preferred embodiment, the exterior is a metal can. That is, the exterior body is a hard case type exterior body. For example, the hard case type exterior body may be a rigid exterior body made of stainless steel (SUS steel), aluminum, or the like. Typically, the hard case type exterior body is composed of a box-shaped main body portion and a lid portion, and at least one of the main body portion and the lid portion is thermally bonded to the outermost layer electrode of the electrode assembly. It is integrated through the part. Preferably, both the main body portion and the lid portion and the outermost layer electrode of the electrode assembly are integrated via the thermal junction portion. The rigidity of the hard case is preferable in terms of fixing or integrating the outermost layer electrode, and therefore, the electrode assembly in a state in which the warp is more preferably reduced or corrected is likely to be obtained.

In another preferred embodiment, the electrode assembly includes an adhesive separator that is directly bonded to the outermost layer electrode. Such an adhesive separator is an adhesive comprising an adhesive layer (for example, polyvinylidene fluoride (PVDF) or an acrylic resin) on a microporous film made of a polyolefin such as polyethylene (PE) or polypropylene (PP). Layers) may be provided.

In the secondary battery of the present invention, the outermost layer electrode is heat-bonded to the inner main surface of the exterior body. Therefore, preferably, the thermal joint portion is provided on the inner surface of the outer body without reaching the outer surface of the outer body. If the thermal junction reaches the outer surface of the exterior body, there is a concern that the electrolytic solution may leak to the outside. In this respect, since the secondary battery of the present invention is a thermal junction portion that does not reach the outer surface of the exterior body, the secondary battery of the present invention is a highly safe battery that does not have such a concern.

Other matters such as more detailed matters and more specific aspects of the secondary battery of the present invention can be found in the above-mentioned [Structure of the secondary battery manufactured by the present invention] and [Characteristics of the manufacturing method of the present invention]. Since it is explained, the explanation is omitted to avoid duplication.

Although the embodiments of the present invention have been described above, they merely exemplify typical examples. Therefore, those skilled in the art will easily understand that the present invention is not limited to this, and various aspects are conceivable.

For example, if the thermal junction has a "rough surface" due to the bonding process, a protective tape may be used to shield the "rough surface", that is, the outermost layer electrode is heated to the exterior. After joining, a tape may be attached to the thermal joint.

Further, in the above aspect, the aspect in which the electrode assembly has a rectangular shape (square and rectangular shape) in a plan view has been mainly described, but the present invention is not limited to such an aspect. For example, as shown in FIG. 9, even if the plan view shape of the electrode assembly, that is, the plan view shape of the outermost layer electrode 110A is “non-rectangular”, the present invention can be similarly implemented. That is, even in the case of a non-rectangular electrode assembly, the outermost layer electrode of the electrode assembly may be heat-bonded to the exterior body. Preferably, the outer edge portion (more preferably, the current collector exposed region and / or the corner portion) of the non-rectangular outermost layer electrode is subjected to a heat bonding treatment to fix the outermost layer electrode 100A and the outer body 200 to each other or fix them to each other. It may be integrated. Even in the case of such a "non-rectangular shape", the outermost layer electrode has reduced / avoided warpage as in the case of "rectangular shape", and the electrode assembly obtained from the electrode assembly can also reduce / avoid warpage. That is, as a result, it is possible to obtain a non-rectangular secondary battery in which a decrease in energy density due to warpage is suppressed.

The term "non-rectangular" as used herein refers to a shape in which the shape of the electrode assembly in a plan view (the same applies hereinafter) is not normally included in the rectangular concept such as square and rectangular, and in particular, the shape thereof. It refers to a shape that is partially missing from a square or rectangle like this. Therefore, in a broad sense, "non-rectangular" refers to a shape in which the shape of the electrode assembly in a plan view seen from above in the thickness direction is not square or rectangular, and in a narrow sense, the shape of the electrode in a plan view is It means that the shape is based on a square / rectangle, but is partially cut out from it (preferably a shape in which the corners of the square / rectangle of the base are cut out). As an example, "non-rectangular" is based on a square / rectangular shape of the electrode assembly in plan view, and is smaller than the base shape in plan view size, square, rectangular, semicircular, or semi-elliptical. , A shape obtained by cutting out a part of a circular or elliptical shape or a combination shape thereof from the base shape (particularly, a shape obtained by cutting out from a corner portion of the base shape) (see FIG. 10).

Furthermore, although the above description has mainly described an embodiment in which a plurality of thermal junctions have a symmetrical positional relationship, the present invention is not limited to such an embodiment. For example, as shown in FIG. 11, the plurality of heat-bonded portions 350 may be heat-bonded so as to have a symmetrical positional relationship. Further, the heat bonding may be performed so that the arrangement form of the plurality of heat bonding portions is "plurality of rows" or "staggered". Even in such an embodiment, the outermost layer electrode whose warpage is reduced / avoided can be obtained, and the electrode assembly obtained from the electrode assembly can also reduce / avoid the warp. Although FIGS. 5 and 6 exemplify thermal junctions having a symmetrical positional relationship, the present invention is not necessarily limited symmetrically, and warpage is reduced even in an asymmetric thermal junction. Certain effects can be achieved. Similarly, in FIGS. 5 and 6, although thermal junctions are provided at all four corners of the outermost layer electrode, thermal junctions may be provided at one of the four corners, in which case. However, a certain effect of warpage reduction can be achieved (that is, in the present invention, at least one of the portions corresponding to the four corners of the outermost layer electrode may be subjected to thermal bonding).

The secondary battery according to the present invention can be used in various fields where storage is expected. Although only an example, secondary batteries are used in the fields of electricity, information, and communication where mobile devices are used (for example, the fields of mobile devices such as mobile phones, smart watches, smartphones, laptop computers, and digital cameras), homes, and so on. Small industrial applications (eg, power tools, golf carts, home / nursing / industrial robots), large industrial applications (eg, forklifts, elevators, bay port cranes), transportation systems (eg, hybrid vehicles) , Electric vehicles, buses, trains, electrically assisted bicycles, electric motorcycles, etc.), power system applications (for example, various power generation, road conditioners, smart grids, general household installation type power storage systems, etc.), and space / deep sea It can be used for various purposes (for example, in the fields of space explorers, submersible research vessels, etc.).

1 Positive electrode 2 Negative electrode 3 Separator 10 Electrode constituent layer 100 Electrode assembly 100A Outer layer electrode 100B Partial electrode assembly 115 Electrode material (electrode material region)
118 Current collector exposed area 119 Outermost layer electrode corner 200 Exterior body 250 Exterior body body 270 Exterior lid 300 Secondary battery 350 Joint / thermal joint

Claims (20)

A method for manufacturing a secondary battery including an electrode assembly having a two-dimensional laminated structure and an exterior body for accommodating the electrode assembly.
The outermost layer electrode used as the outermost layer of the electrode assembly is heat-bonded to the outer body.
The thermal bonding is applied to the outer edge portion of the outermost layer electrode and the corner portion of the outermost layer electrode .
A secondary battery for obtaining an electrode assembly by combining a partial electrode assembly corresponding to a portion other than the outermost layer of the electrode assembly and the outermost layer electrode thermally bonded to the outer body to each other. Production method. The method for manufacturing a secondary battery according to claim 1, wherein the thermal bonding is locally performed in a dot shape or a linear shape. The method for manufacturing a secondary battery according to claim 1 or 2, wherein the heat bonding is performed on an exposed region of a current collector in which an electrode material is not provided in the outermost layer electrode. The method for manufacturing a secondary battery according to any one of claims 1 to 3, wherein the thermal bonding is performed so that at least two thermal bonding portions have a symmetrical positional relationship. The method for manufacturing a secondary battery according to any one of claims 1 to 4, wherein laser welding is performed as the thermal bonding. The method for manufacturing a secondary battery according to any one of claims 1 to 5, wherein as the outermost layer electrode, a single-sided electrode having an electrode material layer provided only on one main surface of a current collector is used. The method for manufacturing a secondary battery according to any one of claims 1 to 6, wherein the outermost layer electrode is a negative electrode. The method for manufacturing a secondary battery according to any one of claims 1 to 7, wherein a hard case type exterior body is used as the exterior body. The method for manufacturing a secondary battery according to claim 1, wherein an adhesive separator is interposed between the outermost layer electrode and the partial electrode assembly. The method for manufacturing a secondary battery according to any one of claims 1 to 9, wherein a positive electrode and a negative electrode capable of occluding and releasing lithium ions are used as electrodes of the electrode assembly. The method for manufacturing a secondary battery according to any one of claims 1 to 10, wherein a protective tape is attached to the heat-bonded portion brought about by the heat-bonding. A secondary battery having an electrode assembly having a flat laminated structure and an exterior body for accommodating the electrode assembly.
A thermal joint portion for joining the outermost layer electrode constituting the outermost layer of the electrode assembly and the outer body to each other is provided .
A secondary battery in which the thermal junction portion is an outer edge portion of the outermost layer electrode and is positioned at a corner portion of the outermost layer electrode. The secondary battery according to claim 12, wherein the thermal junction is positioned with respect to an exposed region of a current collector in which no electrode material is provided in the outermost layer electrode. The secondary battery according to claim 12 or 13, wherein the outermost layer electrode is a single-sided electrode in which an electrode material layer is provided only on one main surface of a current collector. The secondary battery according to any one of claims 12 to 14, wherein the exterior body is a hard case type exterior body. The secondary battery according to any one of claims 12 to 15, wherein the thermal junction forms a punctate or linear local junction. The method according to any one of claims 12 to 16, wherein at least two thermal junctions are provided, and the at least two thermal junctions have a symmetrical positional relationship in a plan view of the outermost layer electrode. Secondary battery. The secondary battery according to any one of claims 12 to 17, wherein the thermal junction is provided on the inner surface of the outer body without reaching the outer surface of the outer body. The secondary battery according to any one of claims 12 to 18, wherein the electrode of the electrode assembly includes a positive electrode and a negative electrode capable of occluding and releasing lithium ions. The secondary battery according to any one of claims 12 to 19, wherein a protective tape is attached to the thermal joint portion.

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