JP6724342B2 - Battery separator, battery having the separator, method for manufacturing the separator, and method for manufacturing the battery - Google Patents

Description

The present invention relates to a battery separator that is processed into a tubular shape so as to accommodate an electrode, and a battery including the separator. The present invention also relates to a method for manufacturing the above separator and a method for manufacturing a battery.

Along with the rapid market expansion of notebook PCs, mobile phones, electric vehicles, etc., electric storage devices such as capacitors and secondary batteries are being actively researched. Above all, the secondary battery is attractive in that it can store more energy. At present, there is a demand for secondary batteries with higher energy density, and it has been proposed to use metals such as tin and silicon or alloys or oxides thereof as a negative electrode active material as candidates. It has also been proposed to use a battery having a large theoretical capacity such as a lithium air battery. However, the higher the energy density of the battery, the larger the energy that can be released, and thus the consideration of safety becomes more important.

For example, in an electricity storage device such as a lithium ion secondary battery, a separator plays a role of preventing a short circuit between a positive electrode and a negative electrode and effectively moving lithium ions. Until now, polyolefin-based microporous separators made of polypropylene or polyethylene materials have been mainly used. The reason is that the shutdown effect of these materials contributes to safety when the battery heats up. However, in the polyolefin microporous separator, the melting points of polypropylene and polyethylene materials are generally 110°C to 160°C. Therefore, when used in a battery having a high energy density, the separator may thermally contract at a high temperature, and the separator may melt before the shutdown effect is obtained, resulting in short circuit between electrodes in a large area.

It has also been proposed to use an inorganic material or an organic polymer-inorganic composite material in a lithium ion battery in place of such an organic polymer separator. Although the inorganic material does not have the above-mentioned shut-down effect, it has a melting point overwhelmingly higher than that of the organic polymer, so that it may be rather excellent in safety. It has also been proposed to use a material having high heat resistance as an organic polymer to prevent the separator from melting or shrinking .

Patent Document 1 (Japanese Patent No. 5644506) discloses a separator using an aramid porous film containing an aramid (aromatic polyamide) resin which is a high heat resistant resin. Patent Document 2 (Japanese Patent No. 5587555) discloses a separator using a polyimide resin which is a highly heat resistant resin.

Patent Document 3 (International Publication No. 2006/095579) discloses a laminated battery using a separator processed into a bag shape. The separator is formed by stacking two sheets of thermoplastic resin and heat-sealing the outer peripheral edges thereof continuously or intermittently. The positive electrode or the negative electrode is housed in the separator, which prevents the separator from being displaced due to vibration during transportation or the like, thereby preventing a short circuit between the positive electrode and the negative electrode.

Patent Document 4 (JP-A-2015-69745) discloses a bag-shaped separator in which at least two sides of a porous film made of an aramid resin are bonded. As a method of bonding the porous film, a method of applying a solvent to the bonding portion and bonding them together, followed by drying, a method of using an adhesive, a method of sandwiching a thermoplastic resin having a low melting point in the bonding portion, and applying pressure and heat treatment, It describes a method in which a porous membrane is subjected to a surface treatment such as low-temperature plasma treatment and then laminated by compression and heating, a method in which a thread made of aramid is sutured, and the like. Patent Document 5 (JP-A-5-290822) discloses a separator containing an amorphous aramid resin and capable of being processed into a bag shape by melting.

Patent Document 6 (Japanese Patent Laid-Open No. 2006-59717) discloses a sheet-shaped or bag-shaped separator made of a fiber assembly containing fibers made of aramid and/or polyimide. As a method for forming a fiber aggregate into a bag shape, a joining method by heat fusion is disclosed. Patent Document 7 (International Publication No. 2014/1999997) also discloses a separator formed in a bag shape by stacking two sheet materials made of a high heat-resistant resin such as an aramid resin and a polyimide resin, and engaging their peripheral portions with each other. It is disclosed.

Patent No. 5644506 Patent No. 5587555 International Publication No. 2006/095579 JP, 2005-69745, A JP-A-5-290822 JP, 2006-59717, A International Publication No. 2014/1999997

It is considered that the problem of heat shrinkage at high temperature is small in the separators described in Patent Documents 1 and 2 that use a highly heat-resistant resin such as an aramid resin or a polyimide resin. However, a separator using a high heat resistant resin cannot be processed into a bag shape by heat fusion, unlike the separator described in Patent Document 3. As a result, when the battery is assembled or the battery is transported, the separator may be displaced and the positive electrode and the negative electrode may be short-circuited.

On the other hand, Patent Document 4 describes several methods of joining a porous film made of an aramid resin without using heat welding, but these methods are industrially used in the following points. There is a problem in production. It is conceivable that the method using a solvent and the method using an adhesive may not be properly joined depending on the method of applying the solvent or the adhesive and the amount of application. In the method using a thermoplastic resin, the thermoplastic resin may be melted at a high temperature and the bonding function may not be fulfilled. The method by stitching is difficult to realize. Further, in the method using the low temperature plasma treatment, since the surfaces of the porous film are bonded to each other, the qualitative contact area on the actual bonding surface is small, and as a result, sufficient bonding strength may not be obtained.

In the separator described in Patent Document 5, the heat resistance of the separator is reduced due to the inclusion of the amorphous aramid resin, resulting in a loss of the original superiority of the high heat resistant resin.

Further, in the method described in Patent Document 6, it is difficult to actually bond the aramid resin or the polyimide resin by heat fusion. Since the method described in Patent Document 7 is joining by mechanical meshing of sheet materials, there is a possibility that sufficient bonding strength cannot be obtained unless a sufficient meshing region is secured.

Therefore, the present invention prevents the positional deviation between the electrode and the separator by allowing the bag-shaped separator to be formed with sufficient bonding strength when the heat-resistant resin is used for the separator, thereby producing the battery. The purpose is to prevent short circuit between electrodes while improving the property.

The separator of the present invention is a separator for a battery in which a positive electrode and a negative electrode are arranged to face each other,
One half-folded porous sheet or two superposed sheets containing a resin having a melting point or a glass transition temperature of 200° C. or higher, which has a first portion and a second portion arranged to face each other. Has a porous sheet of
The porous sheet allows the porous sheet to be connected to the battery by a joint portion that has a portion that extends across the first portion and the second portion and that integrates the first portion and the second portion. It is formed in a tubular shape capable of accommodating the positive electrode or the negative electrode.

The battery of the present invention includes a positive electrode and a negative electrode that are arranged to face each other,
With the separator of the present invention,
Have
The positive electrode or the negative electrode is housed in the separator.

The present invention also provides a separator manufacturing method and a battery manufacturing method. The method for producing the separator of the present invention is a method for producing a separator for a battery in which a positive electrode and a negative electrode are arranged to face each other,
One or two porous sheets containing a resin having a melting point or a glass transition temperature of 200° C. or higher, which are folded in half to form a first portion and a second portion which face each other. A step of preparing two porous sheets, or two porous sheets constituting a first portion and a second portion which face each other by being overlapped with each other;
A binder containing a solvent capable of dissolving or swelling a resin having a melting point or a glass transition temperature of 200° C. or higher is used to form a cylindrical body capable of accommodating the positive electrode or the negative electrode of the battery. A step of forming a joining portion that integrates the first portion and the second portion with a portion that extends across the first portion and the second portion;
Have.

The method for producing a battery of the present invention is a porous sheet containing a resin having a melting point or a glass transition temperature of 200° C. or higher, and has a first portion and a second portion which are opposed to each other when folded in two. A step of preparing one porous sheet that constitutes the above, or two porous sheets that constitute a first portion and a second portion that face each other by being overlapped, a positive electrode and a negative electrode;
Disposing the positive electrode or the negative electrode between the first portion and the second portion,
Using a bonding agent containing a solvent capable of dissolving or swelling a resin having a melting point or glass transition temperature of 200° C. or higher, a cylindrical body capable of accommodating the positive electrode or the negative electrode is formed, A step of forming a joining portion that integrates the first portion and the second portion with a portion that extends over the first portion and the second portion;
After the positive electrode or the negative electrode is disposed between the first portion and the second portion, and the tubular body is formed by the first portion and the second portion, the A step of obtaining an electrode laminate by laminating a positive electrode and the negative electrode,
A step of encapsulating the electrode laminate with an electrolytic solution in an outer casing,
Have.

According to the present invention, since a joining portion for forming a porous sheet containing a heat-resistant resin having a melting point or a glass transition temperature of 200° C. or more into a tubular shape is formed with sufficient joining strength, the porosity at the joining portion is increased. It is possible to obtain a separator in which breakage of the quality sheet is unlikely to occur. By accommodating the positive electrode or the negative electrode in such a separator, positional displacement between the electrode and the separator can be prevented, and a short circuit between the electrodes can be satisfactorily prevented.

1 is an exploded perspective view of a secondary battery according to an exemplary embodiment of the present invention. It is a disassembled perspective view of the electrode laminated body shown in FIG. FIG. 3 is a perspective view of the negative electrode and the separator before the negative electrode shown in FIG. 2 is inserted into the separator. FIG. 3 is an exploded perspective view of a secondary battery according to an exemplary embodiment of the present invention, in which a positive electrode terminal and a negative electrode terminal are pulled out in the same direction. It is a figure explaining an example of the manufacturing method of the separator by this invention. It is a figure explaining the other example of the manufacturing method of the separator by this invention. It is a figure which shows typically one form of the cross section of the junction part of the separator in this invention. It is a figure which shows typically the other form of the cross section of the junction part of the separator in this invention. It is a schematic diagram which shows an example of the electric vehicle provided with the battery of this invention. It is a schematic diagram which shows an example of the electrical storage apparatus provided with the battery of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[Electrode stack and electricity storage device]
The electrode laminate and the electricity storage device can be applied to various devices as long as they can store charges. A typical device is a battery such as a lithium ion secondary battery, but it can be applied to other secondary batteries and further to a capacitor such as an electric double layer capacitor. The following description is an example of lithium ion secondary batteries, but is not limited to this, depending on the type of device to which the present invention is applied, the shape, can be modified in arrangement and material appropriately it can.

There are various types of secondary batteries, such as a cylindrical type, a flat wound rectangular type, a laminated rectangular type, a coin type, a flat wound laminated type, and a laminated laminated type, depending on the structure and shape of the electrodes. The present invention is applicable to any of these types. Among these, the shape of the secondary battery to which the present invention is applied is preferably a laminated laminate type from the viewpoint that the separator is not easily broken. The laminated laminate type secondary battery will be described below.

Referring to FIG. 1, the present invention includes an electrode laminate 10 and an exterior body that encloses the electrode laminate 10 with electrolyte solutions by enclosing the electrode laminate 10 from both sides in the thickness direction with the exterior materials 21 and 22. An exploded perspective view of a secondary battery 1 according to an embodiment of the invention is shown. A negative electrode terminal 31 and a positive electrode terminal 32 are connected to the electrode stack 10 with a part of each protruding from the exterior body.

As shown in FIGS. 2 and 3, the electrode laminated body 10 has a configuration in which a plurality of negative electrodes 11 and a plurality of positive electrodes 12 are arranged to face each other. The separator 13 has a tubular body formed in a tubular shape by using a porous sheet. In the example shown in the drawing, the separator 13 is formed in a bag shape with one end opened and the other end closed, and the positive electrode 12 is inserted from the opened one end side of the separator 13. As a result, the negative electrode 11 and the positive electrode 12 are arranged to face each other with the separator 13 interposed therebetween, and the negative electrode 11 and the positive electrode 12 are kept insulated from each other by the separator 13.

The negative electrode 11 has a negative electrode current collector 11a that can be formed of a metal foil, and a negative electrode active material 11b formed on both surfaces or one surface of the negative electrode current collector 11a. The negative electrode current collector 11a is formed to have an extension extending from a portion facing the separator 13, and the negative electrode active material 11b is not formed in this extension.

Like the negative electrode 11, the positive electrode 12 also has a positive electrode current collector 12a that can be formed of a metal foil, and a positive electrode active material 12b formed on both surfaces or one surface of the positive electrode current collector 12a. The positive electrode current collector 12a is formed to have an extension that extends from the portion housed in the separator 13, and the positive electrode active material 12b is not formed in this extension.

The negative electrode 11 and the positive electrode 12 are stacked so that their respective extensions extend in opposite directions. The extensions of the plurality of negative electrodes 11 are electrically connected by welding to form the negative electrode tab 10a shown in FIG. The extensions of the plurality of positive electrodes 12 are also electrically connected by welding to form the positive electrode tab 10b shown in FIG. The negative electrode terminal 31 is electrically connected to the negative electrode tab 10a, and the positive electrode terminal 32 is electrically connected to the positive electrode tab 10b.

The electrode laminated body 10 having such a planar laminated structure does not have a portion having a small radius of curvature (a region close to the winding core of the wound structure), and therefore, compared with an electrode element having a wound structure, charge/discharge is less likely to occur. There is an advantage that it is unlikely to be affected by the accompanying change in the volume of the electrode. That is, it is effective for an electrode laminated body using an active material that easily causes volume expansion.

In the examples shown in FIGS. 1 to 3, the negative electrode terminal 31 and the positive electrode terminal 32 are drawn out in mutually opposite directions, but the negative electrode terminal 31 and the positive electrode terminal 32 may be drawn out in any directions. For example, as shown in FIG. 4, the negative electrode terminal 31 and the positive electrode terminal 32 may be drawn out from the same side of the electrode laminated body 10, or, although not shown, from the adjacent two sides of the electrode laminated body 10 to the negative electrode terminal 31. The positive electrode terminal 32 may be drawn out. In any case, the extended portion (tab) not covered with the active material of the negative electrode 11 and the positive electrode 12 is formed at a position corresponding to the position where the negative electrode terminal 31 and the positive electrode terminal 32 are drawn out.

Further, in the example shown in the figure, the positive electrode 12 is housed in the separator 13. However, if the negative electrode 11 and the positive electrode 12 can face each other through the separator 13, the negative electrode 11 instead of the positive electrode 12 is separated by the separator 13. It can also be stored in. Further, the negative electrode 11 and the positive electrode 12 may be housed in the separator 13, respectively, and the negative electrode 11 housed in the separator 13 and the positive electrode 12 housed in the separator 13 may be arranged to face each other.

As described above, by making the separator 13 into a tubular shape and housing the negative electrode 11 or the positive electrode 12 therein, it is possible to prevent the separator 13 from being displaced.

Hereinafter, each element constituting the above-described secondary battery will be described in detail.

(Separator)
The separator 13 is configured as a tubular body in which a porous sheet containing a heat-resistant resin as a base material is formed into a flat tubular shape. The tubular body has a size capable of accommodating the positive electrode 12 or the negative electrode 11. By housing the positive electrode 12 or the negative electrode 11 in a tubular body, the positive electrode 12 and the negative electrode 11 are arranged to face each other with the tubular body portion existing between the positive electrode 12 and the negative electrode 11, and the positive electrode 12 and the negative electrode 11 are disposed. It functions as a separator that prevents a short circuit with 11. If the porous sheet does not have electrical conductivity, can prevent a short circuit between the positive electrode 12 and the negative electrode 11, and can configure the tubular body to have ionic conductivity, It may contain any inorganic filler and/or organic filler. Further, the inorganic porous layer may be laminated on the porous sheet.

The heat-resistant resin contained in the porous sheet is preferably a resin having a melting point or glass transition temperature of 200° C. or higher, and more preferably a melting point or glass transition temperature of 250° C. or higher. Examples of such a resin include polyamide resin, aramid resin (aromatic polyimide resin), polyphenylene sulfide resin, polysulfone resin, polyether sulfone resin, polyetherimide resin, polyetheretherketone resin, polyamideimide resin, and the like. To be Examples of the inorganic filler that can be contained in the heat resistant resin or that can form the inorganic porous layer include inorganic oxides such as aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, BaTiO ₂ , ZrO, and alumina-silica composite oxide. Substance particles; inorganic nitride particles such as aluminum nitride and boron nitride; covalent bond crystal particles such as silicone and diamond; sparingly soluble ionic crystal particles such as barium sulfate, calcium fluoride, barium fluoride; clay such as talc and montmorillonite Examples thereof include fine particles. These inorganic fillers may be subjected to element substitution, surface treatment, solid solution treatment, or the like, if necessary. Moreover, these inorganic fillers may be used individually by 1 type, and may be used in combination of 2 or more type. Among these inorganic fillers, the inorganic oxide particles are particularly preferable from the viewpoint of stability in the electrolytic solution and potential stability.

The tubular body may have a bag-like form in which only one end is open and the other end is closed, as well as the form in which both ends are open. The tubular body having only one end opened is capable of holding the positive electrode 12 or the negative electrode 11 more stably, and can more effectively prevent a short circuit between the positive electrode 12 and the negative electrode 11, and therefore can be preferably used.

As shown in FIG. 5, the tubular body includes a first portion 131 and a second portion 132, which are arranged so as to face each other by stacking two porous sheets, at appropriate portions along, for example, an outer edge. It can be constructed by joining. Alternatively, as shown in FIG. 6, the first portion 131 and the second portion 132, which are arranged so as to face each other by folding one porous sheet in two, are joined at an appropriate portion along, for example, the outer edge. The tubular body can also be formed by doing so. In any case, by joining the first portion 131 and the second portion 132, the tubular body is a joining portion that is the portion in which the first portion 131 and the second portion 132 are joined. It has 133. In the joint portion 133, the first portion 131 and the second portion 132 are integrated.

Here, the first portion 131 and the second portion 132 have one separator 13 regardless of whether the one separator 13 is made of one porous sheet or two porous sheets. It means the part of the porous sheet that constitutes it. Further, the first portion 131 and the second portion 132, which are arranged to face each other, preferably have the same size and shape, but if the positive electrode 12 or the negative electrode 11 can be covered, the size and shape are different from each other. May be. In the illustrated form, the first portion 131 and the second portion 132 have the same size and shape.

The bonding portion 133 may be formed after the positive electrode 12 or the negative electrode 11 is arranged between the first portion 131 and the second portion 132, or may be formed before the arrangement. By forming the bonding portion 133 after the positive electrode 12 or the negative electrode 11 is disposed between the first portion 131 and the second portion 132, the positive electrode 12 or the negative electrode 11 is accommodated at the same time when the bonding portion 133 is formed. The separated separator 13 is obtained. Further, when the joining portion 133 is formed before the positive electrode 12 or the negative electrode 11 is disposed between the first portion 131 and the second portion 132, the positive electrode 12 is formed on the tubular separator 13 formed by joining. Alternatively, the negative electrode 11 is inserted, whereby the separator 13 accommodating the positive electrode 12 or the negative electrode 11 is obtained.

A bonding agent can be used to form the bonding portion 133. As the bonding agent, for example, a solvent capable of dissolving or swelling a heat resistant resin having a melting point or a glass transition temperature of 200° C. or higher can be used. Since the heat-resistant resin has a strong intermolecular force, it can be dissolved in a polar solvent in many cases. Examples of such a solvent include N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), chloroform, dichloromethane acetone, tetrahydrofuran ( THF), tetramethylurea (TMUA) and the like.

The solvent is applied to a portion of at least one of the first portion 131 and the second portion 132 of the porous sheet facing each other to form the joint 133. After the application of the solvent, the first portion 131 and the second portion 132 are brought into close contact with each other at least at the solvent-applied portion, and the solvent is removed by drying or the like while maintaining this state.

The applied solvent penetrates into the voids of the porous sheet and dissolves or swells the heat resistant resin. After the application of the solvent, the close contact state between the first portion 131 and the second portion 132 is maintained, so that the dissolution or swelling of the heat-resistant resin by the solvent is caused by both the first portion 131 and the second portion 132. Occurs. As a result, the boundary between the first portion 131 and the second portion 132 substantially disappears in the portion where the solvent is applied, and the voids also substantially disappear. As a result, as schematically shown in FIG. 7, in the joint portion 133 formed by removing the solvent, the first portion 131 and the second portion 132 do not include any other member. It is configured as one layer extending over the first portion 131 and the second portion 132. That is, the joining portion 133 has a portion that extends over the first portion 131 and the second portion 132, and thus the first portion 131 and the second portion 132 are integrated. .. In addition, in the joint portion 133, there is no void, or the void ratio is lower than in other portions.

On the other hand, as the bonding agent, it is also possible to use a solution (hereinafter, referred to as “resin solution”) obtained by dissolving the above-mentioned resin exemplified as the heat-resistant resin contained in the porous sheet in these solvents. Specific examples of such a solution include a solution in which a polyamide resin or an aramid resin (aromatic polyamide resin) is dissolved in NMP, a solution in which a polyphenylene sulfide resin is dissolved in diphenyl ether, NMP or N-Cyclohexylprorolidene, and a polysulfone resin in dichloromethane or methyl. solution in pyrrolidone, polyether sulfone resins NMP, te Tre methyl urea, DMAc, solutions in DMSO or DMF, a solution prepared by dissolving the polyetherimide resin NMP, polyether ether ketone resin DMSO, DMA c, chloroform Alternatively, a solution in which THF is dissolved, a solution in which a polyamideimide resin is dissolved in NMP, DMAc, DMF or DMSO, and the like can be given.

Even when the resin solution is used as the bonding agent, the resin solution forms the bonding portion 133 of the facing surfaces of at least one of the first portion 131 and the second portion 132 of the porous sheet, like the solvent. It is applied to the part to be applied. In addition, after the application, the first portion 131 and the second portion are brought into close contact with each other at least in the portion where the resin solution is applied, and the solvent is removed by drying or the like while maintaining this state. Is the same as when using.

However, the form of integration of the first portion 131 and the second portion 132 is that the solvent in the resin solution is a heat-resistant resin contained in the porous sheet forming the first portion 131 and the second portion 132. It depends on whether it can be dissolved or swollen.

When the solvent in the resin solution is a solvent capable of dissolving or swelling the heat resistant resin contained in the porous sheet, the heat resistant resin is dissolved or swelled by the resin solution. Therefore, as in the case where a solvent is used as the bonding agent, the first portion 131 and second portion 132 are integrated by the junction 133 that is configured as a layer that spans both.

However, when the solvent in the resin solution is a solvent that cannot dissolve or swell the heat-resistant resin contained in the porous sheet, the applied resin solution is in the voids of the first portion 131 and the second portion 132. Penetrate into. When the solvent is removed from the resin solution that has penetrated into the voids, the heat resistant resin in the resin solution remains in the voids and solidifies in the voids. As shown in FIG. 8, of the heat-resistant resin solidified in the voids, the portion 134 existing over both the first portion 131 and the second portion 132 forms the first portion 131 and the second portion 132. It functions as an anchor for fixing, thereby forming a joint 133 in which the first portion 131 and the second portion 132 are integrated. Moreover, the joint 133, the gap of the first portion 131 and second portion 132, since the resin contained in the resin solution is filled, voids have a have substantially present.

As described above, the joint portion 133 between the first portion 131 and the second portion 132 is configured to have the portion that extends over the first portion 131 and the second portion 132. , The 1st part 131 and the 2nd part 132 are joined by sufficient joining strength. As a result, it is possible to obtain the tubular separator 13 in which breakage at the joint 133 is unlikely to occur. By accommodating the positive electrode 12 or the negative electrode 11 in the separator 13 as described above, the positional deviation between the electrodes (the positive electrode 12 and the negative electrode 11) and the separator 13 from the manufacturing of the battery to the completion of the battery is prevented, and the electrode is prevented. A short circuit between them can be effectively prevented.

In addition, the portion of the joint portion 133 that extends over the first portion 131 and the second portion 132 is made of a resin having a melting point or glass transition temperature of 200° C. or higher. Therefore, for example, even when the battery becomes high in temperature due to the occurrence of an abnormality, the portion existing across the battery does not melt or soften, and the joining state between the first portion 131 and the second portion 132 is good. Maintained at.

Upon application of the solvent or resin solution to the porous sheet, the porous sheet has excellent permeability to these solvents or resin solutions, and the porosity of the porous sheet is lost in the region where the solvent or resin solution has permeated. .. Therefore, if the coating amount of the solvent or the resin solution is too large, the region where the porosity is lost spreads too much and the function as the separator 13 may be lost. Therefore, it is important that the coating amount of the solvent or resin solution is sufficiently controlled. As a coating method capable of controlling the coating amount well, for example, a method of transferring a solvent or a resin solution to a porous sheet using a stamp, a method of ejecting the solvent or the resin solution from a fine nozzle (inkjet method) or spraying Method (spray method), a method of adding a trace amount of a solvent or a resin solution with a microdispenser, and the like.

The bonding portion 133 may be partially formed or may be linearly continuously formed as long as it is located around the positive electrode 12 or the negative electrode 11. However, the joint strength of the joint portion 133 depends on the area of the joint portion, and generally, the larger the joint portion area is, the higher the joint strength can be obtained, so that the separator 13 can maintain a good tubular shape. In order to achieve this, it is preferable that the joint portion 133 be formed in a linear shape. From this point of view, when the joint portion 133 is partially formed, the joint portion 133 is preferably formed in a dotted line shape. When the joining portion 133 is formed in a dotted line shape, when the positive electrode 12 or the negative electrode 11 housed in the separator 13 is impregnated with the electrolytic solution, the electrolytic solution easily enters the separator 13 through the dotted line gap of the joining portion 133. Become. As a result, the manufacturing time of the battery can be shortened.

The width of the joining portion 133 is preferably 0.05 mm or more in order to favorably join the first portion 131 and the second portion 132, and from the viewpoint that higher joining strength can be obtained. , 0.1 mm or more is more preferable. On the other hand, if the width of the bonding portion 133 is too wide, the area of the separator 13 becomes larger than the area of the positive electrode 12 or the negative electrode 11 that is housed, which leads to an increase in the size of the battery itself. This means that the battery capacity per unit volume decreases or the battery capacity per unit weight decreases. Therefore, the width of the joint portion 133 is preferably 3 mm or less, more preferably 1 mm or less.

Here, the width of the joint portion 133 refers to a dimension in a direction perpendicular to the length direction of the joint portion 133 when viewed from the outer surface of the separator 13. The separator 13 is made of a porous sheet and has a large number of voids. However, as described above, the joint portion 133 has no voids or has a low void ratio as compared with other portions. ing. Therefore, the separator 13 separates the joint portion 133 and the portion other than the joint portion 133 from the difference in light transmittance due to the difference in porosity, for example, by visual observation or enlarged observation from the outer surface of the separator 131. Can be distinguished.

The coating amount of the solvent or resin solution for forming the joint 133 is preferably ^{0.1μL / cm 2 ~3μL / cm 2} , in particular, a thickness of 15 to 30 [mu] m, porosity of 30 to 30% When applied to a porous sheet, it is preferably 0.45 μL/cm ^{2 to} 2.4 μL/cm ² . According to the above-described coating method capable of controlling the coating amount well, it is possible to easily coat the solvent or resin solution with such a coating amount. Further, in the case of applying by transfer, in order to apply an appropriate amount of the solvent or the resin solution, it is preferable that at least a portion serving as a transfer surface of the stamp is made of a nonwoven fabric or a porous body.

When the solvent or resin solution is applied to the porous sheet, the applied solvent or resin solution actually permeates and spreads in the voids of the porous sheet. Therefore, in order to set the width of the finally obtained joint portion 133 to the preferable width as described above, it is preferable that the coating width of the solvent or the resin solution be a width in consideration of its spread. However, when coating the coating amount, as described above for the well manageable coating method, since it can be suppressed to Rio minimum Hiroga solvent or resin solution, coating width of a solvent or resin solution in the junction 133 You can think that it is substantially equal to the width.

After applying the solvent or the resin solution, in order to promote the bonding between the first portion 131 and the second portion 132 of the porous sheet, the first portion 131 and the second portion are formed in the region where the solvent or the resin solution is applied. It is preferable to press 132 and. Furthermore, when pressure is applied while irradiating the region to be the joint portion 133 with ultrasonic waves, the melted heat-resistant resin (the heat-resistant resin here is defined as the heat-resistant resin at the boundary between the first portion 131 and the second portion 132). The heat-resistant resin contained in the porous sheet may be used, or the heat-resistant resin contained in the resin solution may be mixed.

When removing the solvent, it is preferable to heat the part of the porous sheet coated with the solvent or the resin solution. This accelerates the removal of the solvent by volatilization. Further, when the solvent is a solvent capable of dissolving the heat-resistant resin of the porous sheet, it is possible to accelerate the dissolution of the porous sheet by the solvent in the solvent application section. The heating temperature of the porous sheet at this time is preferably 30° C. or higher, and more preferably 50° C. or higher. The higher the heating temperature, the more accelerated the dissolution of the porous sheet. However, at a temperature close to the boiling point of the solvent, volatility becomes too high, and it may be difficult to bond the first portion 131 and the second portion 132. From this viewpoint, the heating temperature of the porous sheet is preferably equal to or lower than the boiling point of the solvent, more preferably 30° C. or more lower than the boiling point of the solvent, and further preferably 50° C. or more lower than the boiling point of the solvent. .. The heating for removing the solvent is preferably performed in a reduced pressure environment. As a result, the vapor pressure of the solvent can be increased even at a temperature below the boiling point, and as a result, the solvent can be dried and removed without causing thermal deterioration of the heat-resistant resin and other materials.

As the form of the porous sheet, any form such as a porous film, a fiber aggregate such as a woven fabric or a non-woven fabric, and a microporous membrane can be adopted. Among them, the microporous film is particularly preferable because lithium is less likely to be deposited and a short circuit between the positive electrode and the negative electrode can be suppressed. Further, it is preferable that the porous sheet has a smaller void size on the surface on the negative electrode side because lithium deposition can be suppressed.

The porosity of the porous sheet can be appropriately set according to the characteristics required as a pallet. For example, in order to obtain good rate characteristics of the battery, the porosity is preferably 35% or more, more preferably 40% or more. In order to increase the mechanical strength of the separator, the porosity of the porous sheet is preferably 80% or less, more preferably 70% or less.

The porosity of the porous sheet can be calculated by measuring the bulk density according to JIS P 8118 and using the following formula.

Other methods for measuring the porosity include a direct observation method with an electron microscope and a press-fitting method with a mercury porosimeter.

The average void diameter of the porous sheet is preferably 1 μm or less, more preferably 0.5 μm or less, still more preferably 0.1 μm or less. Further, in order to allow the charged body to permeate well, the porous sheet preferably has a pore size of 0.005 μm or more on the surface of the negative electrode side, and more preferably 0.01 μm or more.

As an example of the average void diameter, the average void diameter of the porous sheet is about 0.5 μm in the case of a microporous film made of an aramid resin, about 0.3 μm in the case of a microporous film made of a polyimide resin, and from a polyphenylene sulfide resin. In the case of the microporous film, the thickness may be about 0.5 μm.

The void diameter of the porous sheet can be determined by the bubble point method and the mean flow method described in STM-F-316. In addition, the average void diameter can be the average value of the measured values obtained by measuring the void diameters at any five points on the porous sheet.

The thickness of the porous sheet is preferably thick from the viewpoint of maintaining insulation and mechanical strength. On the other hand, from the viewpoint of improving the energy density of the battery, the thinner one is preferable. As a specific value, the thickness of the porous sheet is preferably 3 μm or more, more preferably 5 μm or more, further preferably 8 μm or more in order to prevent short circuit between the positive electrode and the negative electrode and to impart sufficient heat resistance. .. On the other hand, the thickness of the porous sheet is preferably 40 μm or less, more preferably 30 μm or less, and further preferably 25 μm or less in order to comply with battery specifications such as energy density that is usually required. As an example, in any of the microporous film made of aramid resin, the microporous film made of polyimide resin, and the microporous film made of polyphenylene sulfide resin, the thickness of the porous sheet can be about 20 μm.

The thickness Ts of the insulating layer can be used as an index indicating the insulating property of the separator at high temperature. The porous sheet has voids, and the electrode mixture layer also has voids. The electrodes and the separator may locally reach 400° C. due to overcharge or the like. Therefore, in this case, the insulating property at 400° C. is important. The resin that melts at 400° C. or lower loses the voids of the separator, and thus the insulating performance deteriorates. Further, the melted resin enters the voids of the electrode mixture layer, so that the gap between the electrodes is narrowed and the insulation performance is deteriorated. The thickness (Ts) of the insulating layer at 400° C. is preferably 3 μm or more, and more preferably 5 μm or more.

An inorganic porous layer can be laminated on the porous sheet. An inorganic binder and an organic binder can be used for laminating the inorganic porous layer. The inorganic binder is not particularly limited, and silica-based materials, alumina-based materials, silica-alumina-based materials, aluminum-based, aluminum phosphate-based materials, silver-based materials and the like can be used. As the organic binder, polyvinylidene fluoride (PVdF), polyethylene oxide (PEO), polyacrylonitrile (PAN), polymethylmethacrylate (PMMA) and copolymers of these polymers can be preferably used. As these binders, a single material may be used, or a mixture of two or more materials may be used.

The ionic conductivity value of the separator has a large effect on the internal resistance value of the battery, and thus a larger value is preferable. For example, the electrolytic solution of the lithium secondary battery is 10 ⁻³ S/cm, and it is desirable that the electrolytic solution is 10 ⁻⁴ to 10 ⁻⁶ S/cm in the state of being immersed.

(Negative electrode)
The negative electrode has a structure in which a negative electrode active material is laminated on a current collector as a negative electrode active material layer integrated with a negative electrode binder. The negative electrode active material is a material capable of reversibly receiving and releasing lithium ions as it is charged and discharged.

In one embodiment of the present invention, the negative electrode contains a metal and/or a metal oxide and carbon as a negative electrode active material. Examples of the metal include Li, Al, Si, Pb, Sn, In, Bi, Ag, Ba, Ca, Hg, Pd, Pt, Te, Zn, La, and alloys of two or more of these. .. Moreover, you may use these metals or alloys in mixture of 2 or more types. Also, these metals or alloys may contain one or more non-metallic elements.

Examples of the metal oxide include silicon oxide, aluminum oxide, tin oxide, indium oxide, zinc oxide, lithium oxide, or a composite of these. In the present embodiment, the negative electrode active material preferably contains tin oxide or silicon oxide, and more preferably contains silicon oxide. This is because silicon oxide is relatively stable and does not easily cause a reaction with other compounds. Further, one or more elements selected from nitrogen, boron and sulfur may be added to the metal oxide, for example, in an amount of 0.1 to 5 mass %. By doing so, the electrical conductivity of the metal oxide can be improved. Further, the electric conductivity can be similarly improved by coating the metal or metal oxide with a conductive material such as carbon by a method such as vapor deposition.

Examples of carbon include graphite, amorphous carbon, diamond-like carbon, carbon nanotubes, and composites thereof. Here, graphite having high crystallinity has high electric conductivity, and has excellent adhesiveness to a negative electrode current collector made of a metal such as copper and excellent voltage flatness. On the other hand, since amorphous carbon having low crystallinity has a relatively small volume expansion, it has a high effect of alleviating the volume expansion of the entire negative electrode and is less likely to be deteriorated due to nonuniformity such as grain boundaries and defects.

Metals and metal oxides are characterized by a much higher lithium-accepting capacity than carbon. Therefore, the energy density of the battery can be improved by using a large amount of metal and metal oxide as the negative electrode active material. In order to achieve a high energy density, the content ratio of the metal and/or metal oxide in the negative electrode active material is preferably high, and the amount of carbon contained in the negative electrode that can be accepted by lithium is larger than the amount of lithium that can be released by the positive electrode. Metal and/or metal oxides are incorporated in the negative electrode so that the amount thereof is small. In the present specification, the amount of lithium that can be released from the positive electrode and the amount of carbon that can be received by lithium contained in the negative electrode mean the respective theoretical capacities. The ratio of the amount of lithium contained in the negative electrode that can be received by lithium to the amount of lithium that can be released from the positive electrode is preferably 0.95 or less, more preferably 0.9 or less, and further preferably 0.8 or less. The more the amount of the metal and/or the metal oxide is, the more the capacity of the negative electrode as a whole is increased, which is preferable. The metal and/or metal oxide is preferably contained in the negative electrode in an amount of 0.01% by mass or more of the negative electrode active material, more preferably 0.1% by mass or more, still more preferably 1% by mass or more. However, the metal and/or metal oxide has a large volume change when occluding/releasing lithium as compared with carbon, and may lose electrical bonding. Therefore, 99% by mass or less, preferably 90% by mass or less is preferable. It is not more than 80% by mass, more preferably not more than 80% by mass. As described above, the negative electrode active material is a material capable of reversibly receiving and releasing lithium ions as the negative electrode is charged and discharged, and does not include any other binder.

As the binder for the negative electrode, polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, styrene-butadiene copolymer rubber, polytetrafluoroethylene, polypropylene, polyethylene, Acrylic, polyimide, polyamideimide, etc. can be used. Other than the above, styrene butadiene rubber (SBR) and the like can be mentioned. When an aqueous binder such as SBR emulsion is used, a thickener such as carboxymethyl cellulose (CMC) can also be used. The amount of the negative electrode binder used is preferably 0.5 to 20 parts by mass with respect to 100 parts by mass of the negative electrode active material, from the viewpoint of sufficient binding force and high energy which are in a trade-off relationship. The above-mentioned binder for the negative electrode may be mixed and used.

The negative electrode active material can be used together with the conductive auxiliary material. Specific examples of the conductive auxiliary material include the same materials as those specifically exemplified for the positive electrode, and the amount thereof used may be the same.

As the negative electrode current collector, aluminum, nickel, stainless steel, chromium, copper, silver, and alloys thereof are preferable from the viewpoint of electrochemical stability. Examples of the shape include foil, flat plate, and mesh.

A conductive auxiliary material may be added to the coating layer containing the negative electrode active material for the purpose of lowering impedance. Examples of the conductive auxiliary material include scale-like, soot-like, and fibrous carbonaceous fine particles, such as graphite, carbon black, acetylene black, and vapor grown carbon fiber (VGCF (registered trademark) manufactured by Showa Denko KK).

Examples of the method for forming the negative electrode active material layer include a doctor blade method, a die coater method, a CVD method, and a sputtering method. After forming the negative electrode active material layer in advance, a thin film of aluminum, nickel, or an alloy thereof may be formed by a method such as vapor deposition or sputtering to serve as the negative electrode current collector.

(Positive electrode)
The positive electrode refers to an electrode on the high potential side in the battery, and includes, for example, a positive electrode active material capable of reversibly receiving and releasing lithium ions with charge and discharge, and the positive electrode active material is a positive electrode binder. It has a structure in which it is laminated on the current collector as an integrated positive electrode active material layer. In one embodiment of the present invention, the positive electrode has a charge capacity per unit area of 3 mAh/cm ² or more, preferably 3.5 mAh/cm ² or more. In addition, from the viewpoint of safety, the charge capacity of the positive electrode per unit area is preferably 15 mAh/cm ² or less. Here, the charge capacity per unit area is calculated from the theoretical capacity of the active material. That is, the charge capacity of the positive electrode per unit area is calculated by (theoretical capacity of the positive electrode active material used for the positive electrode)/(area of the positive electrode). The area of the positive electrode refers to the area of one surface of the positive electrode, not both surfaces.

In order to increase the energy density of the positive electrode, the positive electrode active material used for the positive electrode receives and releases lithium and is preferably a compound having a higher capacity. Examples of the high-capacity compound include a lithium nickel composite oxide obtained by substituting a part of Ni of nickel lithium oxide (LiNiO ₂ ) with another metal element, and a layered lithium nickel composite oxide represented by the following formula (A). The thing is preferable.

Li _y Ni _(1-x) M _x O ₂ (A)
(However, 0≦x<1, 0<y≦1.2, and M is at least one element selected from the group consisting of Co, Al, Mn, Fe, Ti, and B.)

From the viewpoint of high capacity, the content of Ni is high, that is, in the formula (A), x is preferably less than 0.5, more preferably 0.4 or less. Examples of such a compound include Li _α Ni _β Co _γ Mn _δ O ₂ (0<α≦1.2, preferably 1≦α≦1.2, β+γ+δ=1, β≧0.7, γ≦0 .2), Li _α Ni _β Co _γ Al _δ O ₂ (0<α≦1.2, preferably 1≦α≦1.2, β+γ+δ=1, β≧0.6, preferably β≧0.7, γ ≦0.2) and the like, and particularly LiNi _β Co _γ Mn _δ O ₂ (0.75≦β≦0.85, 0.05≦γ≦0.15, 0.10≦δ≦0.20 ) Is mentioned. More specifically, for _{example, LiNi 0.8 Co 0.05 Mn 0.15 O} 2, LiNi 0.8 Co 0.1 Mn 0.1 O 2, LiNi 0.8 Co 0.15 Al 0.05 O ₂ , LiNi _0.8 Co _0.1 Al _0.1 O _{2 and the} like can be preferably used.

From the viewpoint of thermal stability, it is also preferable that the Ni content does not exceed 0.5, that is, x in the formula (A) is 0.5 or more. It is also preferable that the number of specific transition metals does not exceed half. As such a compound, Li _α Ni _β Co _γ Mn _δ O ₂ (0<α≦1.2, preferably 1≦α≦1.2, β+γ+δ=1, 0.2≦β≦0.5, 0 1≦γ≦0.4, 0.1≦δ≦0.4). More specifically, LiNi _0.4 Co _0.3 Mn _0.3 O ₂ (abbreviated as NCM433), LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiNi _0.5 Co _0.2 Mn. _0.3 O ₂ (abbreviated as NCM523), LiNi _0.5 Co _0.3 Mn _0.2 O ₂ (abbreviated as NCM532), etc. (However, the content of each transition metal in these compounds varies by about 10%. (Including those that have been done).

Further, two or more compounds represented by the formula (A) may be mixed and used, and for example, NCM532 or NCM523 and NCM433 in a range of 9:1 to 1:9 (as a typical example, 2 It is also preferable to use the mixture in 1). Further, in the formula (A), a material having a high Ni content (x is 0.4 or less) and a material having a Ni content not exceeding 0.5 (x is 0.5 or more, for example, NCM433) are mixed. By doing so, a battery with high capacity and high thermal stability can be constructed.

In addition to the above, examples of the positive electrode active material include LiMnO ₂ , Li _x Mn ₂ O ₄ (0<x<2), Li ₂ MnO ₃ , Li _x Mn _1.5 Ni _0.5 O ₄ (0<x< 2) Lithium manganate having a layered structure or spinel structure such as; LiCoO ₂ or some of these transition metals replaced with other metals; Li in these lithium transition metal oxides rather than stoichiometric composition Excessive ones; and those having an olivine structure such as LiFePO ₄ are included. Further, materials obtained by partially replacing these metal oxides with Al, Fe, P, Ti, Si, Pb, Sn, In, Bi, Ag, Ba, Ca, Hg, Pd, Pt, Te, Zn, La, etc. Can also be used. Each of the positive electrode active materials described above can be used alone or in combination of two or more.

As the positive electrode binder, the same binder as the negative electrode binder can be used. Among them, from the viewpoint of versatility and low cost, polyvinylidene fluoride or polytetrafluoroethylene is preferable, and polyvinylidene fluoride is more preferable. The amount of the positive electrode binder used is preferably 2 to 10 parts by mass with respect to 100 parts by mass of the positive electrode active material, from the viewpoints of “sufficient binding force” and “energy increase” which are in a trade-off relationship. ..

A conductive auxiliary material may be added to the coating layer containing the positive electrode active material for the purpose of lowering impedance. Examples of the conductive auxiliary material include scale-like, soot-like, fibrous carbonaceous fine particles and the like, for example, graphite, carbon black, acetylene black, vapor grown carbon fiber (for example, VGCF manufactured by Showa Denko) and the like.

As the positive electrode current collector, the same one as the negative electrode current collector can be used. In particular, as the positive electrode, a collector made of aluminum, aluminum alloy, iron/nickel/chromium/molybdenum-based stainless steel is preferable.

Like the negative electrode, the positive electrode can be produced by forming a positive electrode active material layer containing a positive electrode active material and a positive electrode binder on a positive electrode current collector.

(Electrolyte)
The electrolytic solution of the lithium-ion secondary battery according to this embodiment is not particularly limited, but a non-aqueous electrolytic solution containing a non-aqueous solvent and a supporting salt that is stable at the operating potential of the battery is preferable.

Examples of the non-aqueous solvent include propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), and other cyclic carbonates; dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC), Chain carbonates such as dipropyl carbonate (DPC); propylene carbonate derivatives, aliphatic carboxylic acid esters such as methyl formate, methyl acetate, ethyl propionate; ethers such as diethyl ether and ethyl propyl ether, trimethyl phosphate, Aprotic organic solvents such as phosphoric acid esters such as triethyl phosphate, tripropyl phosphate, trioctyl phosphate, triphenyl phosphate, and fluorine in which at least a part of hydrogen atoms of these compounds are substituted with fluorine atoms. Aprotic organic solvent and the like.

In a secondary battery containing a metal or a metal oxide in the negative electrode, they may deteriorate and disintegrate, which may increase the surface area and accelerate the decomposition of the electrolytic solution. The gas generated by the decomposition of the electrolytic solution is one of the factors that inhibit the acceptance of lithium ions in the negative electrode. Therefore, in the lithium ion secondary battery having a large content ratio of the metal and/or the metal oxide in the negative electrode as in the present invention, a solvent having high oxidation resistance and hardly decomposed is preferable. Examples of the solvent having strong oxidation resistance include fluorinated aprotic organic solvents such as fluorinated ethers and fluorinated phosphates.

In addition, cyclic such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylmethyl carbonate (MEC), dipropyl carbonate (DPC) or the like. Chain carbonates are also mentioned as particularly preferable solvents.

The non-aqueous solvent may be used alone or in combination of two or more.

As the supporting _{salt, LiPF 6, LiAsF 6, LiAlCl} 4, LiClO 4, LiBF 4, LiSbF 6, LiCF 3 SO 3, LiC 4 F 9 SO 3, LiC (CF 3 SO 2) 3, LiN (CF 3 SO 2 ) ₂ etc. lithium salt is mentioned. The supporting salts may be used alone or in combination of two or more. LiPF ₆ is preferable from the viewpoint of cost reduction.

The electrolytic solution may further contain an additive. The additive is not particularly limited, and examples thereof include halogenated cyclic carbonate, unsaturated cyclic carbonate, and cyclic or chain disulfonic acid ester. By adding these compounds, battery characteristics such as cycle characteristics can be improved. It is presumed that this is because these additives are decomposed during charge/discharge of the lithium ion secondary battery to form a film on the surface of the electrode active material and suppress decomposition of the electrolytic solution and the supporting salt.

Next, a method of manufacturing the above-mentioned battery and an application example thereof will be described.

[Method of manufacturing secondary battery]
The above-mentioned laminated laminate type lithium ion secondary battery can be produced, for example, as follows. First, the plurality of positive electrodes 12 and the plurality of negative electrodes 11 are manufactured as described above.

Next, in dry air or an inert atmosphere, a positive electrode-containing separator in which the positive electrode 12 is housed in a cylindrical separator 13 is manufactured. As described above, the positive electrode-containing separator is manufactured by arranging the positive electrode 12 between the first portion 131 and the second portion 132 and then joining the first portion 131 and the second portion 132. Can be made. In this case, the bonding portion 133 may be formed over the entire circumference of the positive electrode 12 except for the portion where the positive electrode tab 10b extends from the separator 13. Alternatively, after the tubular separator 13 in which the first portion 131 and the second portion 132 are joined on the two sides or the three sides is manufactured, the positive electrode 12 is inserted into the separator 13 to form the positive electrode-containing separator. It can also be made. In this case, after the positive electrode 12 is inserted into the separator 13, the first portion 131 and the second portion 132 are joined at the remaining unjoined sides, so that the positive electrode tab 10b extends from the separator 13. The bonding portion 133 can be formed over the entire circumference of the positive electrode 12 except for.

A plurality of positive electrode-containing separators are produced as described above, and these are alternately stacked on the negative electrode 11. At this time, the orientations of the positive electrode-containing separator and the negative electrode 11 are aligned for each of the negative electrode 11 and the positive electrode-containing separator, and the extension portions of the negative electrode 11 and the extension portions of the positive electrode 12 are joined to form the negative electrode tab 10a and the positive electrode tab 10b. Form. As a result, the electrode stack 10 in which the plurality of positive electrodes 12 and the plurality of negative electrodes 11 are stacked with the separator 13 in between is manufactured. The number of stacked positive electrodes 12 and negative electrodes 11 is determined according to the intended capacity of the battery. In the above example, only the positive electrode 12 is stored in the separator 13, but it is also possible to store only the negative electrode 11 in the separator 13.

Next, the negative electrode terminal 31 is joined to the negative electrode tab 10a, and the positive electrode terminal 32 is joined to the positive electrode end portion 10b. After joining these terminals, the electrode laminate 10 is housed in the exterior body. When the laminate film is used as the outer package, the electrode laminate 10 can be stored in the outer package by heat-sealing the laminate film around the electrode laminate 10. At this time, the negative electrode detection 31 and the positive electrode terminal 32 are in a state of protruding from the exterior body. In addition, the laminate film is heat-sealed, leaving a portion to be an opening for injecting an electrolytic solution in a later step.

After housing the electrode laminate 10 in the outer package, the electrolytic solution is injected from the opening of the outer package to impregnate the electrode laminate 10 with the electrolytic solution. After that, the opening is sealed, and thus the secondary battery is manufactured.

The battery having the above-described laminated structure is one of the preferable modes in which the present invention can obtain a large operational effect because the separator is likely to be deformed or displaced due to thermal contraction when a general separator is used.

[Battery pack]
A plurality of secondary batteries can be combined to form an assembled battery. The assembled battery can be configured, for example, by connecting two or more secondary batteries according to the present embodiment in series and/or in parallel. The number of series and the number of parallel of the secondary batteries can be appropriately selected according to the target voltage and capacity similarity of the assembled battery.

[vehicle]
The secondary battery or the assembled battery thereof described above can be used in a vehicle. Vehicles that can use secondary batteries or assembled batteries include hybrid vehicles, fuel cell vehicles, and electric vehicles (all are four-wheel vehicles (commercial vehicles such as passenger cars, trucks, buses, and light vehicles), as well as two-wheel vehicles (motorcycles). And including tricycles). The vehicle according to the present embodiment is not limited to an automobile, but can be used as various power sources for other vehicles, for example, a moving body such as a train. As an example of such a vehicle, FIG. 9 shows a schematic diagram of an electric vehicle. The electric vehicle 200 shown in FIG. 9 includes a plurality of secondary batteries connected in series and in parallel, and has an assembled battery 210 configured to satisfy the required voltage and capacity.

[Power storage device]
The secondary battery or the assembled battery thereof described above can be used for a power storage device. As a power storage device using a secondary battery or an assembled battery, for example, it is connected between a commercial power supply supplied to a general home and a load such as a home electric appliance, and used as a backup power supply or an auxiliary power supply at the time of power failure. There are also those used for large-scale electric power storage, such as solar power generation, for stabilizing electric power output with large time fluctuation due to renewable energy. An example of such a power storage device is schematically shown in FIG. A power storage device 300 shown in FIG. 10 includes a plurality of secondary batteries connected in series and in parallel, and includes an assembled battery 310 configured to satisfy a required voltage and capacity.

[Other]
Furthermore, the above-mentioned secondary battery or its assembled battery can be used as a power source for mobile devices such as mobile phones and notebook computers.

Hereinafter, the present invention will be specifically described with reference to examples.

[Example 1]
(Preparation of positive electrode)
Layered lithium nickel composite oxide (LiNi _0.8 Co _1.5 Al _0.05 O ₂ ), carbon black (trade name: “#3030B”, manufactured by Mitsubishi Chemical Corporation), and polyvinylidene fluoride (trade name: "W#7200" manufactured by Kureha Co., Ltd.) were weighed at a mass ratio of 93:2:5, respectively. These were mixed with N-methylpyrrolidone (NMP) to obtain a slurry. The mass ratio of NMP and solid content was 54:46. This slurry was applied as a positive electrode active material to a 15 μm thick aluminum foil (positive electrode current collector) using a doctor blade. The aluminum foil coated with this slurry was heated at 120° C. for 5 minutes to dry the NMP to prepare a positive electrode.

(Preparation of negative electrode)
A 1% by mass aqueous solution of artificial graphite and carboxymethylcellulose (CMC) was kneaded using a rotation/revolution mixer (Awatori Rentaro ARE-500 manufactured by Shinky Co., Ltd.), and then a styrene-butadiene copolymer (SBR) was added. A negative electrode slurry was prepared. The mass ratio of artificial graphite, CMC and SBR was 97:1:2. This slurry was applied as a negative electrode active material onto a copper foil (negative electrode current collector) having a thickness of 10 μm with a doctor blade, and then dried by heating at 110° C. for 5 minutes to prepare a negative electrode.

(Preparation of separator)
For the separator, a single layer wholly aromatic polyamide (aramid) microporous membrane was used as a porous sheet. The aramid microporous membrane had a thickness of 25 μm, an average void diameter of 0.5 μm, and a porosity of 60%. This aramid microporous membrane was cut into a rectangular shape and two pieces were stacked. Next, the two stacked aramid microporous membranes were placed on a hot plate at 80°C, folded in two and pressed with NMP-impregnated filter paper along the three sides of the peripheral portion of the aramid microporous membrane to transfer the NMP. did. It was confirmed by a gravimetric method that the amount of NMP applied was 1.0 μL/cm ² in a separately performed transfer test at room temperature without using a hot plate. The aramid microporous membrane was left as it was on a hot plate for 1 hour. As a result, a bag-shaped separator was obtained in which the joint portion where the two aramid microporous membranes were integrated at the portion where NMP was transferred was linearly formed along the three sides of the aramid microporous membrane. When the weight of the obtained separator was measured, it was confirmed that NMP was dried and lost. In addition, the width of the obtained joint portion was 0.1 mm. Furthermore, the bondability of the obtained separator was evaluated by visually confirming the bonded portion.

Further, the obtained separator was heated on a hot plate at 200° C. for 10 minutes for the purpose of confirming heat resistance and shrinkage of the bonded portion. With respect to the separator after heating, the presence or absence of peeling and the presence or absence of shrinkage at the joint were visually checked to evaluate the heat resistance and the shrinkability.

(Preparation of secondary battery)
Next, a plurality of positive electrodes were cut out so as to have an uncoated portion of the positive electrode active material that became the positive electrode tab. A plurality of the cut-out positive electrodes were stored one by one in a bag-shaped separator in dry air or an inert atmosphere. Similarly to the positive electrode, a plurality of negative electrodes were cut out so that the negative electrode had an uncoated portion of the negative electrode active material that became the negative electrode tab. A plurality of positive electrodes and a plurality of negative electrodes stored in the separator were alternately stacked so that the uncoated portions of the active materials were in opposite directions to form an electrode laminate. The uncoated portions of the positive electrode active material of the positive electrode were collectively joined to the positive electrode terminal, and the uncoated portions of the negative electrode active material of the negative electrode were collectively joined to the negative electrode terminal. Next, this electrode laminated body was housed in an exterior body (container), and a nonaqueous electrolytic solution was injected to impregnate the electrode laminated body with the electrolytic solution. As the electrolytic solution, a solution containing 1.0 mol/l of LiPF ₆ as an electrolyte and a mixed solvent (7:3 (volume ratio)) of ethylene carbonate and diethyl carbonate as a non-aqueous electrolytic solvent was used. Then, the opening of the outer package was sealed to complete the secondary battery.

Vibration was applied to the secondary battery manufactured as described above. The vibration was a sweep vibration that returned from the frequency of 7 Hz to 7 Hz through 200 Hz in 15 minutes, and 12 sets were performed for each of the three directions of X, Y, and Z. After giving vibration to the battery, the initial discharge capacity was measured. The conditions of the first charge/discharge were a current of 0.05 C, an environment of 20° C., an upper limit of 4.2 V and a lower limit of 2.5 V. At this time, what could not be charged due to a short circuit was counted as a short circuit after the vibration test.

[Example 2]
A secondary battery was manufactured in the same manner as in Example 1 except that an NMP solution in which 10% by mass of an aramid resin was dissolved was used to bond the porous sheets in the production of the separator, and the same evaluation as in Example 1 was performed. went.

[Example 3]
A polyimide microporous film (thickness 20 μm, average void diameter 0.3 μm, porosity 80%) is used as the porous sheet, and the coating amount of the solution applied to form a bag-shaped joint is 3 μL/cm. ^A secondary battery was produced in the same manner as in Example 2 except that the number was changed to 2, and the same evaluation as in Example 1 was performed.

[Example 4]
A secondary battery was prepared in the same manner as in Example 2 except that a polyphenylene sulfide microporous membrane (thickness 20 μm, average void diameter 0.5 μm, porosity 40%) was used as the porous sheet, and the same as Example 1. An evaluation was made.

[Example 5]
A secondary battery was produced in the same manner as in Example 1 except that the temperature of the hot plate used for joining the porous sheets was 120° C., and the same evaluation as in Example 1 was performed.

[Example 6]
A secondary battery was produced in the same manner as in Example 3 except that the temperature of the hot plate used for joining the porous sheets was 120° C., and the same evaluation as in Example 1 was performed.

[Example 7]
Except that the coating fabric of NMP was used for bonding of the porous sheet was 10 [mu] L / cm @ 2 is then produced in the same manner as in the secondary battery in Example 1 and subjected to the same evaluation as in Example 1. Workability was poor because wrinkles were formed at the joined portion of the porous sheet, and it took twice as long as Example 1 to store the positive electrode.

[Comparative Example 1]
A polyimide microporous film (thickness 20 μm, average void diameter 0.3 μm, porosity 80%) is used as a porous sheet, and the coating amount of NMP applied to form a bag-shaped joint is 3 μL/cm. ^A secondary battery was produced in the same manner as in Example 1 except that the number was changed to ² , and the same evaluation as in Example 1 was performed. However, since the porous sheet was not joined and the bag-shaped separator could not be obtained, the positive electrode and the negative electrode were alternately laminated, and after each tab was bonded to the electrode terminal, the sheet-shaped separator was interposed between the electrodes. An electrode laminated body was formed by sandwiching.

[Comparative example 2]
A secondary battery was produced in the same manner as in Example 1 except that ethanol was used to join the porous sheets in the production of the separator, and the same evaluation as in Example 1 was performed. However, since the porous sheet was not joined and the bag-shaped separator could not be obtained, the positive electrode and the negative electrode were alternately laminated, and after each tab was bonded to the electrode terminal, the sheet-shaped separator was interposed between the electrodes. A sandwich was formed by sandwiching.

[Comparative Example 3]
A secondary battery was produced in the same manner as in Example 1 except that a toluene solution in which a polystyrene resin was dissolved in 10% by mass was used to bond the porous sheets in the production of the separator, and the same evaluation as in Example 1 was performed. went.

Table 1 shows, for Examples 1 to 7 and Comparative Examples 1 to 3, main preparation conditions of the separator, evaluation results of the joint portion of the porous sheet, and vibration test results of the obtained secondary batteries. In Table 1, the evaluation results of the bondability are represented by “◯” for those without peeling and “x” for those with peeling. The evaluation results of the heat resistance of the joints are represented by “◯” when the occurrence of peeling was not observed, and by “x” when the occurrence of peeling was observed. The shrinkage evaluation result is ``○'' if no change in appearance such as wrinkling due to shrinkage before and after heating or deformation of the separator was observed, and no shrinkage was observed but wrinkles around the joint. Those that were observed were indicated by “Δ”, and those that were observed in appearance changes before and after heating, such as wrinkles other than at the joints and deformation of the separator, are indicated by “x”.

In each of Examples 1, 5 and 7, a microporous membrane made of aramid was used as a porous sheet, and then NMP capable of dissolving aramid was used as a bonding agent to form a bag. Processing was possible. However, in Example 5, since the temperature at the time of joining was high, the drying was quick but the solubility was high, and the result was that the uniform joining property was poor. In addition, since the excessive amount of NMP was used in Example 7, the bonding agent could not be applied in a uniform linear shape to the microporous membrane having high impregnating property, and wrinkle-like particles were formed as compared with Examples 1 and 5. A joint having a spread was formed. On the other hand, in Comparative Example 1, NMP was used as the bonding agent, but a microporous film made of polyimide was used as the porous sheet. The polyimide did not dissolve or swell in NMP, and as a result, the polyimide microporous film could not be joined.

In Examples 2, 3, 4 and 6, an aramid solution was used as the bonding agent. The aramid solution does not dissolve the polyimide microporous membrane used as the porous sheet in Examples 3 and 6. However, since the aramid resin that has penetrated into the voids of the polyimide microporous film functions as an anchor, the polyimide microporous film could be processed into a bag shape. Further, since the aramid resin is a heat-resistant resin, peeling did not occur at the joint even when heated to 200°C. Therefore, it can be expected that safety can be ensured even if the battery is placed in an abnormally high temperature environment.

Similar to Example 5, Example 6 was bonded at a high temperature of 120° C. However, since the polyimide microporous film used in Example 6 was not dissolved in the NMP solvent, wrinkles did not occur at the bonded portion.

In Comparative Example 2, ethanol was used as the binder. Similar to Comparative Example 1, since the aramid microporous membrane used as the porous sheet in Comparative Example 2 was not dissolved in ethanol, the aramid microporous membrane could not be processed into a bag shape. In Comparative Example 3, a toluene solution of polystyrene resin was used as the bonding agent. The aramid microporous membrane used as the porous sheet in Comparative Example 3 was not dissolved in toluene, but since the polystyrene resin functions as an anchor, it was possible to bond the aramid microporous membrane. However, there was no heat resistance at 200°C, and peeling of the joint occurred. Further, since the polystyrene resin is soluble in the electrolytic solution, it was often peeled off and short-circuited during the vibration test.

Although the present invention has been described in detail above by the embodiments and examples, the present specification discloses the following inventions.

[1] A battery separator 13 in which a positive electrode 12 and a negative electrode 11 are arranged to face each other,
One folded or two porous sheets containing a resin having a melting point or a glass transition temperature of 200° C. or higher having a first portion 131 and a second portion 132 which are arranged opposite to each other Has two porous sheets,
The porous sheet is formed by a joint 133 that has a portion that extends over the first portion 131 and the second portion 132 and that integrates the first portion 131 and the second portion 132. Is a cylindrical separator 13 that can accommodate the positive electrode 12 or the negative electrode 11 of the battery.

[2] The separator 13 according to [1], wherein the porous sheet further contains an inorganic filler.

[3] The separator according to [1] or [2], wherein the porous sheet is a microporous film having an average void diameter of 1 μm or less.

[4] The joining portion 133 is configured as a single layer that extends over the first portion 131 and the second portion 132, whereby the first portion 131 and the second portion 132 are integrated. The separator according to any one of [1] to [3], which has been embodied.

[5] In the joint portion 133, a melting point or glass that fills the voids of the first portion 131 and the voids of the second portion 132 across the first portion 131 and the second portion 132. The separator according to any one of [1] to [3], in which the first portion 131 and the second portion 132 are integrated by an anchor made of a resin having a transition temperature of 200° C. or higher.

[6] The separator according to [5], wherein the resin forming the anchor is a resin different from the resin contained in the porous sheet.

[7] The separator according to any one of [1] to [6], in which the porosity at the joint portion 133 is lower than the porosity at portions other than the joint portion.

[8] The separator according to [7], in which there are no voids in the joint 133.

[9] The separator according to any one of [1] to [8], wherein the resin contained in the porous sheet is a wholly aromatic polyamide resin, a polyimide resin, or a polyphenylene sulfide resin.

[10] A positive electrode 12 and a negative electrode 11 arranged to face each other,
A separator 13 according to any one of [1] to [9],
Have
A battery in which the positive electrode 12 or the negative electrode 11 is housed in the separator 13.

[11] A method for manufacturing a battery separator 13 in which a positive electrode 12 and a negative electrode 11 are arranged to face each other,
1. One or two porous sheets containing a resin having a melting point or a glass transition temperature of 200° C. or higher, and constituting a first portion 131 and a second portion 132 which face each other by being folded in two. A step of preparing one of the porous sheets, or a step of preparing two of the porous sheets that constitute a first portion 131 and a second portion 132 that face each other by being overlapped with each other;
By using a bonding agent containing a solvent capable of dissolving or swelling a resin having a melting point or a glass transition temperature of 200° C. or higher, a tubular body capable of housing the positive electrode 12 or the negative electrode 11 of the battery is formed. , A joint portion 133 that integrates the first portion 131 and the second portion 132 is formed to have a portion that extends across the first portion 131 and the second portion 132. Process,
A method of manufacturing a separator having:

[12] The step of forming the joint 133 includes
Overlapping the first portion 131 and the second portion 132 with each other;
A solvent capable of dissolving or swelling the resin contained in the porous sheet is applied as the bonding agent to a region serving as the front bonding portion 133 of at least one of the first portion 131 and the second portion 132. The process of
Removing the solvent after the first portion 131 and the second portion 132 are overlapped with each other and the bonding agent is applied;
[11] The method for producing the separator according to [11].

[13] The step of forming the joint 133 includes
As the bonding agent, a step of obtaining a solution in which a resin having a melting point or a glass transition temperature of 200° C. is dissolved in a solvent,
Overlapping the first portion 131 and the second portion 132 with each other;
Applying the bonding agent to a region that will be the bonding portion 133 of at least one of the first portion 131 and the second portion 132;
Removing the solvent from the bonding agent after the first portion 131 and the second portion 132 are overlapped with each other and the bonding agent is applied;
[11] The method for producing the separator according to [11].

[14] The method for producing a separator according to [13], wherein the solvent contained in the bonding agent is a solvent capable of dissolving or swelling the resin contained in the porous sheet.

[15] The resin contained in the bonding agent is a resin different from the resin contained in the porous sheet, and the solvent contained in the bonding agent can dissolve or swell the resin contained in the bonding agent. Is a resin that cannot dissolve or swell the resin contained in the porous sheet, [13].

[16] In the step of applying the bonding agent, the first portion 131 and the second portion 132 are opposed to each other before the first portion 131 and the second portion 132 are overlapped with each other. The method for producing a separator according to any one of [12] to [15], which comprises applying the bonding agent to at least one of the surfaces.

[17] In the step of applying the bonding agent, after the first portion 131 and the second portion 132 are overlapped with each other, the outer surface of at least one of the first portion 131 and the second portion 132 is removed. The method for producing a separator according to any one of [12] to [15], which comprises applying the bonding agent to the surface.

[18] In the step of applying the bonding agent, the porous material impregnated with the bonding agent is pressed onto the area to be the bonding section 133 to transfer the bonding agent to the area to be the bonding section 133. The method for producing the separator according to any one of [12] to [17], which comprises:

[19] The method for producing a separator according to any one of [12] to [18], wherein the step of removing the solvent includes heating the first portion 131 and the second portion 132.

[20] The method for producing a separator according to any one of [12] to [19], wherein the step of removing the solvent is performed under reduced pressure.

[21] A porous sheet containing a resin having a melting point or a glass transition temperature of 200° C. or higher, which is a single sheet that constitutes a first portion 131 and a second portion that face each other by being folded in two. A porous sheet, or a step of preparing two porous sheets, a positive electrode 12 and a negative electrode 11, which constitute a first portion 131 and a second portion 132 which are opposed to each other by being overlapped,
Disposing the positive electrode 12 or the negative electrode 11 between the first portion 131 and the second portion 132,
A binder containing a solvent capable of dissolving or swelling a resin having a melting point or glass transition temperature of 200° C. or higher is used to form a cylindrical body capable of accommodating the positive electrode 12 or the negative electrode 11, A step of forming a joining portion 133 that integrates the first portion 131 and the second portion 132 with a portion that extends over the first portion 131 and the second portion 132. When,
The positive electrode 12 or the negative electrode 11 is disposed between the first portion 131 and the second portion 132, and the tubular body is formed by the first portion 131 and the second portion 132. After being formed, a step of obtaining the electrode laminate 10 by laminating the positive electrode 12 and the negative electrode 11;
A step of encapsulating the electrode laminated body 10 together with an electrolytic solution in an outer casing,
Of manufacturing a battery having a.

INDUSTRIAL APPLICABILITY The present invention can be used in all industrial fields requiring a power source, and industrial fields related to transportation, storage and supply of electric energy. Specifically, power sources for mobile devices such as mobile phones and laptops; power sources for mobile and transportation media such as trains, satellites, and submarines, including electric vehicles such as electric vehicles, hybrid cars, electric motorcycles, and electric assist bicycles. It can be used as a backup power source such as UPS; a power storage facility that stores power generated by solar power generation, wind power generation, and the like.

DESCRIPTION OF SYMBOLS 1 Secondary battery 10 Electrode element 11 Negative electrode 12 Positive electrode 13 Separator 21, 22 Exterior material 31 Negative electrode terminal 32 Positive electrode terminal

Claims (16)

A separator for a battery in which a positive electrode and a negative electrode are arranged to face each other,
One half-folded porous sheet or two superposed sheets containing a resin having a melting point or a glass transition temperature of 200° C. or higher, which has a first portion and a second portion arranged to face each other. Has a porous sheet of
The joint that having a portion present across said second portion and said first portion, said porous sheet is formed into a cylindrical shape that allows housing the positive or negative electrode of the battery,
In the joint part, the melting point or the glass transition temperature is 200° C. or higher, and the first part and the second part are integrated by an anchor made of a resin different from the resin contained in the porous sheet. Separator. Wherein in the joint portion, the first portion and the second portion and the across at the first portion the the void by the anchor to fill the void of the second portion first portion and the second The separator according to claim 1, which is integrated with the part of. The separator according to claim 1 or 2, wherein the anchor is made of aramid resin. The separator according to claim 3, wherein the porous sheet is a polyimide microporous film. The separator according to any one of claims 1 to 4, wherein the porous sheet is formed in a bag shape in which one end is open and the other end is closed. A positive electrode and a negative electrode arranged to face each other,
A separator according to any one of claims 1 to 5 ,
Have
A battery in which the positive electrode or the negative electrode is housed in the separator. A method for manufacturing a separator for a battery, in which a positive electrode and a negative electrode are opposed to each other,
One or two porous sheets containing a resin having a melting point or a glass transition temperature of 200° C. or higher, which are folded in half to form a first portion and a second portion which face each other. A step of preparing two porous sheets, or two porous sheets constituting a first portion and a second portion which face each other by being overlapped with each other;
Joining that integrates the first portion and the second portion so that a cylindrical body that can accommodate the positive electrode or the negative electrode of the battery is formed on the porous sheet by using a bonding agent. Forming the portion with an anchor that extends over the first portion and the second portion,
Have a,
The step of forming the joint includes
As the bonding agent, a resin having a melting point or a glass transition temperature of 200° C. or higher, and a resin different from the resin contained in the porous sheet is a solvent that cannot dissolve or swell the resin contained in the porous sheet. Obtaining a dissolved solution,
Superimposing the first portion and the second portion on each other,
Applying the bonding agent to at least one of the first portion and the second portion, which is the bonding portion,
Removing the solvent from the bonding agent after the first portion and the second portion are overlaid on each other and the bonding agent is applied;
A method of manufacturing a separator having : The said anchor fills the space|gap of the said 1st part and the space|gap of the said 2nd part, straddling the said 1st part and the said 2nd part.
A method for manufacturing the described separator. The method for producing a separator according to claim 7, wherein the resin contained in the bonding agent is an aramid resin. The method for manufacturing a separator according to claim 9, wherein the porous sheet is a microporous polyimide film. The method for producing a separator according to claim 7, wherein the step of forming the joint portion includes forming the porous sheet into a bag shape having one end opened and the other end closed. .. A porous sheet containing a resin having a melting point or a glass transition temperature of 200° C. or higher, and a single porous sheet that constitutes a first portion and a second portion that face each other by being folded in two, Alternatively, a step of preparing two porous sheets, a positive electrode and a negative electrode, which constitute a first portion and a second portion which face each other by being overlapped with each other,
Disposing the positive electrode or the negative electrode between the first portion and the second portion,
A joining portion that integrates the first portion and the second portion so that a tubular body that can accommodate the positive electrode or the negative electrode is formed on the porous sheet by using a joining agent. Forming an anchor having an anchor that extends over the first portion and the second portion,
After the positive electrode or the negative electrode is disposed between the first portion and the second portion, and the tubular body is formed by the first portion and the second portion, the A step of obtaining an electrode laminate by laminating a positive electrode and the negative electrode,
A step of encapsulating the electrode laminate with an electrolytic solution in an outer casing,
Have a,
The step of forming the joint includes
As the bonding agent, a resin having a melting point or a glass transition temperature of 200° C. or higher, and a resin different from the resin contained in the porous sheet is a solvent that cannot dissolve or swell the resin contained in the porous sheet. Melted
Obtaining a solution,
Superimposing the first portion and the second portion on each other,
Applying the bonding agent to at least one of the first portion and the second portion, which is the bonding portion,
Removing the solvent from the bonding agent after the first portion and the second portion are overlaid on each other and the bonding agent is applied;
Method for producing a battery to have a. The battery manufacturing method according to claim 12, wherein the anchor fills the voids of the first portion and the voids of the second portion while straddling the first portion and the second portion. The method for manufacturing a battery according to claim 12, wherein the resin contained in the bonding agent is an aramid resin. The battery manufacturing method according to claim 14, wherein the porous sheet is a microporous polyimide film. 16. The method for manufacturing a battery according to claim 12, wherein the step of forming the bonding portion includes forming the porous sheet into a bag shape in which one end is open and the other end is closed. ..

Images