JP2009043715A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery excellent in cycle characteristic. <P>SOLUTION: The nonaqueous electrolyte secondary battery includes a positive electrode, a negative electrode, a porous insulating layer, and nonaqueous electrolyte. The porous insulating layer is interposed between the positive electrode and the negative electrode. The nonaqueous electrolyte is contained at least in the porous insulating layer. The mixture layer of the positive electrode and the porous insulating layer each include a structure retainer. As the structure retainer, a ceramic particle of a dendrite, carbon fiber or the like is used, and expansion in a thickness direction of a negative electrode active substance layer is controlled. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a non-aqueous electrolyte secondary battery.

  2. Description of the Related Art In recent years, electronic devices have become rapidly portable and cordless, and there is an increasing demand for using a secondary battery that is small and lightweight and has a high energy density as a driving power source for such electronic devices. In addition, it is proposed that secondary batteries be used not only for power sources for small consumer devices, but also for power sources for long-term durability such as power storage power sources or electric vehicle power sources. Technology development for secondary batteries is accelerating.

  Among secondary batteries, non-aqueous electrolyte secondary batteries, particularly lithium ion secondary batteries, have a high voltage and a high energy density. Therefore, the nonaqueous electrolyte secondary battery is expected as a power source for electronic devices, a power source for power storage, or a power source for electric vehicles.

The nonaqueous electrolyte secondary battery includes a positive electrode, a negative electrode, a separator, and a nonaqueous electrolyte. The separator is interposed between the positive electrode and the negative electrode, and a polyolefin microporous film is mainly used for the separator. The non-aqueous electrolyte is held at least in the separator, and a liquid non-aqueous electrolyte in which a lithium salt such as LiBF ₄ or LiPF ₆ is dissolved in an aprotic organic solvent is used as the non-aqueous electrolyte. Moreover, an active material (for example, LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , LiFePO ₄ ) having a high potential with respect to lithium and capable of electrochemically occluding and releasing lithium ions is used as the positive electrode active material, Non-aqueous electrolyte secondary batteries using various carbon materials such as graphite or metal oxides are being put into practical use.

  In such a non-aqueous electrolyte secondary battery, during charging, lithium ions are inserted from the positive electrode active material between the crystal layers of the negative electrode active material, and during discharge, lithium ions are inserted between the negative electrode active material crystals between the positive electrode active material crystals. Return to material. Therefore, when the nonaqueous electrolyte secondary battery is charged and discharged, the positive electrode active material and the negative electrode active material expand or contract.

  Specifically, the positive electrode active material releases lithium ions during charging and returns to the lithium ions during discharging. Here, the active material of the positive electrode exists as lithium oxide, lithium phosphate or lithium sulfate, and the crystal structure of these lithium oxide, lithium phosphate or lithium sulfate is a layered rock salt structure In addition, since it has a strong skeleton such as a spinel structure or an olivine structure, expansion or contraction of the active material of the positive electrode due to the entry and exit of lithium is very small.

  On the other hand, in the negative electrode active material, the lithium active material expands by charging because the lithium ions widen the gap between the crystal layers of the negative electrode active material and enter the crystal layer during charging. When an alloy is used as the negative electrode active material, the expansion of the negative electrode active material is very large.

  If the active material of the negative electrode expands, the positive electrode and the separator may be compressed. When the positive electrode and the separator are compressed, pores existing in the positive electrode mixture layer and the separator are crushed. Since the non-aqueous electrolyte is held in the pores, when the pores are crushed, clogging occurs and the non-aqueous electrolyte is pushed out of the pores. As a result, the battery capacity may decrease (cycle characteristics deteriorate) as the charge / discharge cycle is performed. Therefore, it is preferable to suppress the expansion of the negative electrode active material during charging.

In order to improve the decrease in capacity as a charge / discharge cycle is performed, a method of mixing vapor grown carbon fiber (VGCF) in the negative electrode has been proposed (see Patent Document 1). In Patent Document 1, since the vapor-grown carbon fiber absorbs the expansion and compression of the active material of the negative electrode, the deformation of the negative electrode can be suppressed, and as a result, the capacity decreases as the charge / discharge cycle is performed. It can be suppressed.
Japanese Patent Laid-Open No. 10-162811

  However, even if the technique disclosed in Patent Document 1 is used, it is difficult to completely suppress the expansion of the active material of the negative electrode. Therefore, as described above, the separator and the positive electrode are crushed due to the expansion of the active material of the negative electrode, and the pores existing in the mixture layer of the separator and the positive electrode are crushed. As a result, the non-water that was present in the pores There is a risk that the electrolyte will be pushed out of the pores. Therefore, there is a problem that the cycle characteristics are deteriorated.

  In addition, in the demand for higher capacity of nonaqueous electrolyte secondary batteries, an active material having a higher capacity than a carbon material such as an alloy, metal oxide, or Si oxide is desired as an active material for the negative electrode. When such a high-capacity active material is used, more lithium ions can be inserted between the crystal layers of the active material of the negative electrode than when a carbon material such as graphite is used as the active material. Becomes higher. Therefore, even if the technique disclosed in Patent Document 1 is used, the expansion of the negative electrode active material may not be sufficiently suppressed.

  Furthermore, recently, a negative electrode in which the negative electrode active material is vacuum-deposited on the surface of the negative electrode current collector has been studied. In such a negative electrode, it is difficult to use the method disclosed in Patent Document 1.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve such problems and to provide a nonaqueous electrolyte secondary battery excellent in cycle characteristics.

  The nonaqueous electrolyte secondary battery of the present invention includes a positive electrode, a negative electrode, a porous insulating layer, and a nonaqueous electrolyte. The positive electrode has a mixture layer containing an active material capable of electrochemically occluding and releasing lithium ions. The negative electrode has a layer containing an active material capable of electrochemically inserting and extracting lithium ions (hereinafter referred to as “active material layer of negative electrode”). The porous insulating layer is disposed between the positive electrode and the negative electrode. The nonaqueous electrolyte is held at least in the porous insulating layer. The positive electrode mixture layer includes a structure holding member, and the porous insulating layer includes a structure holding member or includes the structure holding member.

  In the nonaqueous electrolyte secondary battery of the present invention, since the porous insulating layer and the positive electrode mixture layer include the structure holding member, even if the active material of the negative electrode tries to expand, the expansion can be suppressed, that is, the expanded layer has expanded. It can suppress that a separator and a positive electrode are crushed by the negative electrode. Thereby, it can suppress that a nonaqueous electrolyte is extruded from the void | hole which exists in each of the separator and the positive mix layer, and can suppress the fall of cycling characteristics.

  According to the present invention, the cycle characteristics are excellent.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited to embodiment shown below.

  The non-aqueous electrolyte secondary battery according to this embodiment includes a positive electrode, a negative electrode, a porous insulating layer, and a non-aqueous electrolyte. In the positive electrode, a mixture layer is provided on both sides or one side of the current collector, and in the positive electrode mixture layer, an active material, a binder, and a conductive agent capable of electrochemically inserting and extracting lithium ions are provided. include. In the negative electrode, an active material layer containing an active material is provided on both surfaces or one surface of the current collector, and the active material of the negative electrode is a material capable of electrochemically occluding and releasing lithium ions. The porous insulating layer is disposed between the positive electrode and the negative electrode. The nonaqueous electrolyte is held by the positive electrode, the negative electrode, and the separator. A structure holding member is provided in each of the positive electrode mixture layer and the porous insulating layer.

  As described above, in the nonaqueous electrolyte secondary battery according to the present embodiment, since the structure holding member is included in the mixture layer and the porous insulating layer of the positive electrode, the active material of the negative electrode expands during charging. The positive electrode and the porous insulating layer can be prevented from being crushed. As a result, even if the active material of the negative electrode expands, it is possible to suppress the nonaqueous electrolyte from being pushed out from the pores existing in the positive electrode mixture layer and the porous insulating layer, and it is possible to suppress a decrease in cycle characteristics.

  The structure holding member will be described with reference to FIGS. 1A to 1C schematically show the compression force (force for compressing the positive electrode or the porous insulating layer) generated as a result of expansion of the negative electrode active material A by charging. FIG. 1A shows a case where both the inhibitor that suppresses the expansion of the active material A of the negative electrode and the structure holding member are not provided, and FIG. In FIG. 1C, the structure holding member is provided only in the active material layer N, but the structure holding member is not provided. FIG. The case where it is provided in the agent layer P and the porous insulating layer I is shown. 1A to 1C, Fx, Fy, and Fz are the magnitudes of compressive forces in the x-axis direction, the y-axis direction, and the z-axis direction, respectively. The x-axis direction is a direction perpendicular to the paper surface, the y-axis direction is the horizontal direction of the paper surface, and the z-axis direction is the vertical direction of the paper surface.

  Here, the inhibitor is a material that isotropically suppresses the expansion of the negative electrode active material as disclosed in Patent Document 1, and the structure holding member is the negative electrode active material in particular among the negative electrode active material expansion. It is a material that suppresses expansion in the layer thickness direction of the layer.

  Generally, when a non-aqueous electrolyte secondary battery is charged, lithium ions in the positive electrode active material are inserted between the crystal layers of the negative electrode active material, and as a result, the negative electrode active material expands.

  When the inhibitor and the structure holding member are not present, the active material A of the negative electrode expands isotropically as shown in FIG. Therefore, Fx (1) ≈Fy (1) ≈Fz (1). Thus, since the negative electrode active material A expands in the z-axis direction (the thickness direction of the negative electrode active material layer) shown in FIG. 1A, the separator I and the positive electrode have a compressive force (Fz (1) ≠ 0). As a result, the positive electrode mixture layer P and the separator I are compressed. The positive electrode mixture layer P and the separator I have pores for holding the non-aqueous electrolyte, but the pores are crushed by compression, causing clogging, and the non-aqueous electrolyte is removed from the pores. It will be pushed out.

  In addition, when the inhibitor is present in the negative electrode active material layer N as shown in Patent Document 1, as shown in FIG. 1B, the inhibitor (not shown) is the expansion of the negative electrode active material A. Isotropically suppressed. Therefore, Fx (2) <Fx (1), Fy (2) <Fy (1), Fz (2) <Fz (1), but Fx (2) ≒ Fy (2) ≒ Fz (2) ≠ 0. Therefore, it is difficult to suppress the positive electrode mixture layer P and the separator I from being compressed.

  On the other hand, when a structure holding member (not shown) is present in the positive electrode mixture layer P and in the porous insulating layer I as in the nonaqueous electrolyte secondary battery according to the present embodiment, the positive electrode mixture layer Even if a compressive force is applied to P and the porous insulating layer I, the holding force for maintaining the structure of the positive electrode mixture layer P and the porous insulating layer I is repelled by the compressive force and applied to the negative electrode. Since the holding force is applied from the positive electrode mixture layer P and the porous insulating layer I to the negative electrode in this way, the negative electrode active material A can be suppressed from expanding in the z-axis direction as shown in FIG. Fz (3) ≈0) As a result, it is possible to prevent the positive electrode mixture layer P and the porous insulating layer I from being compressed. Therefore, since it can suppress that the void | hole which exists in the mixture layer P of the positive electrode and the porous insulating layer I is crushed, it can suppress that a nonaqueous electrolyte is extruded from the void | hole. As a result, deterioration of cycle characteristics can be prevented.

  Further, the negative electrode active material expands in the x-axis direction and the y-axis direction so as to fill vacancies existing in the negative electrode active material layer during charging even if expansion in the z-axis direction is suppressed in this way. (Fx (3) ≠ 0, Fy (3) ≠ 0). Therefore, in the nonaqueous electrolyte secondary battery according to the present embodiment, the mixture layer of the positive electrode and the separator can be prevented from being crushed without deteriorating the charging characteristics.

  The inhibitor shown in Patent Document 1 isotropically suppresses the expansion of the negative electrode active material A. Therefore, in the case shown in FIG. 1B, in other words, as shown in Patent Document 1, when the inhibitor is present in the negative electrode active material layer N, the expansion of the negative electrode active material A is completely suppressed. As a result, lithium ions cannot enter the crystal layer of the active material of the negative electrode during charging, which may cause deterioration of charging characteristics.

  It is preferable that the structure holding member is also included in the active material layer of the negative electrode. Thereby, since expansion of the active material of the negative electrode is suppressed, compression of the positive electrode mixture layer and the porous insulating layer can be further suppressed.

  In summary, in the present embodiment, the structure holding member is provided in the mixture layer and the porous insulating layer of the positive electrode, and more preferably in the active material layer of the negative electrode. . When the structure holding member is provided in the positive electrode mixture layer and in the porous insulating layer, the structure of the positive electrode mixture layer and the porous insulating layer is held. As a result, in the thickness direction of the active material layer of the negative electrode Expansion of the negative electrode active material is suppressed. Therefore, the structure holding member functions as a compression resistant member in the positive electrode mixture layer and the porous insulating layer. On the other hand, when the structure holding member is provided in the active material layer of the negative electrode, expansion of the active material of the negative electrode is suppressed. In other words, the structure holding member functions as an expansion resistant member in the active material layer of the negative electrode.

  The structure holding member is preferably provided in both the positive electrode mixture layer and the porous insulating layer. This is because if the structure holding member is provided only in the positive electrode mixture layer, the compressive force due to the expansion of the negative electrode active material concentrates on the porous insulating layer, and the porous insulating layer may be compressed. Because. Similarly, if the structure holding member is provided only in the porous insulating layer, the compressive force due to the expansion of the negative electrode active material is concentrated on the positive electrode mixture layer, and the positive electrode mixture layer may be compressed. Because there is.

  The shape of the structure holding member is preferably a shape that is not easily clogged by the structure holding member alone, that is, a shape that does not increase the tap density. The shape of the structure holding member is preferably, for example, a shape with a high aspect ratio, a shape in which yarns are intertwined, a dendritic shape, or a rhomboid shape. Thereby, since the structure holding members are entangled with each other, the compression resistance of the positive electrode mixture layer and the porous insulating layer can be improved, and the expansion resistance of the active material layer of the negative electrode can be improved. be able to. Specific description will be given below.

  The structure holding member present in the porous insulating layer is preferably ceramic particles. Since the ceramic particles are not easily crushed even when an external force is applied, the compression resistance of the porous insulating layer can be improved. Moreover, since the ceramic particles are excellent in insulation, insulation between the positive electrode and the negative electrode can be ensured.

  As the ceramic particles, it is preferable to use ceramic particles having a dendritic shape. When the shape is dendritic, the individual ceramic particles are entangled with each other, so that the compression resistance of the porous insulating layer can be further improved as compared with the case where, for example, spherical ceramic particles are used.

  Here, the porous insulating layer may include a structure holding member or may be formed of a structure holding member. The case where the porous insulating layer is made of the structure holding member includes not only the case where the structure holding member literally consists of only the structure holding member but also the case where the structure holding members are bonded to each other via an adhesive or the like. For example, when the structure holding member is ceramic particles as described above, the porous insulating layer may be composed of an adhesive resin or a resin such as polyethylene, polypropylene, or polyimide and ceramic particles, or a plurality of them. The ceramic particles may be bonded to each other.

  The structure holding member present in the mixture layer of the positive electrode may be a ceramic particle having a dendritic shape or may be a carbon fiber. When ceramic particles having a dendritic shape are used, as described above, the individual ceramic particles are entangled with each other, so that the compression resistance of the mixture layer of the positive electrode can be improved. The present inventors have confirmed that although the ceramic particles have insulating properties, the output characteristics of the battery can be secured even if the ceramic particles are provided in the positive electrode mixture layer. The reason for this is not clear, but it is possible to improve the compression resistance of the positive electrode mixture layer by putting ceramic particles in the positive electrode mixture layer. Therefore, ensure the passage of the nonaqueous electrolyte in the positive electrode mixture layer. The present inventors consider that this is possible.

  Further, when carbon fibers are used, the individual carbon fibers are entangled with each other, so that the compression resistance of the mixture layer of the positive electrode can be improved. Moreover, since carbon fiber is excellent in electroconductivity, the electroconductivity of the positive mix layer can be ensured.

  The structure holding member present in the active material layer of the negative electrode is preferably carbon fiber. It can suppress that the active material of a negative electrode expand | swells because each carbon fiber becomes mutually entangled.

  Specific examples of the material of the structure holding member will be further shown.

  When ceramic particles are provided as a structure holding member in the porous insulating layer and in the positive electrode mixture layer, the ceramic particles may be used alone or in combination of metal oxides, metal nitrides, metal carbides, etc. Can do. Among metal oxides, metal nitrides, and metal carbides, it is preferable to use metal oxides for reasons such as availability. As the metal oxide, alumina (aluminum oxide), titania (titanium oxide), zirconia (zirconium oxide), magnesia (magnesium oxide), zinc oxide, silica (silicon oxide), or the like can be used. Of these metal oxides, alumina is preferable, and α-alumina is particularly preferable. α-alumina is chemically stable, and high purity is particularly chemically stable. “Chemically stable” means, for example, that it is not attacked by the non-aqueous electrolyte even when it is in contact with the non-aqueous electrolyte, and that it does not decompose or react even when a redox potential is applied to the positive electrode and the negative electrode It does not cause side reactions that adversely affect battery characteristics.

  As the particle diameter of the ceramic particles, the average particle diameter of the single crystal is preferably about 0.05 μm to 1 μm. The shape of the ceramic particles may be a spherical shape formed by agglomerating normal primary particles by van der Waals force. However, as shown in FIG. It is desirable to have a shape. In the ceramic particle shown in FIG. 2, since the grown single crystal nuclei are connected, the polycrystalline particle 21 is not spherical but usually has a bump, a bulge, or a bulge, and preferably has a dendritic shape or a cocoon shape. Or it is tufted. As the ceramic particles, it is preferable that a so-called neck is formed at a connecting portion for connecting single crystal nuclei (see FIG. 2), but even a particle in which the neck cannot be clearly distinguished can be used.

  Ceramic particles containing such polycrystalline particles can be obtained, for example, by going through a step of firing a ceramic precursor to obtain a ceramic fired body and a step of mechanically crushing the ceramic fired body. The ceramic fired body has a structure in which the nuclei of grown single crystals are three-dimensionally connected. If such a fired body is mechanically and appropriately crushed, ceramic particles containing polycrystalline particles can be obtained. The ceramic particles are preferably composed of polycrystalline particles, but particles other than polycrystalline particles, such as spherical or nearly spherical primary particles or spherical particles formed by agglomeration of primary particles by van der Waals force, for example, It may contain less than 30% by weight.

  The porous insulating layer is preferably composed of ceramic particles and a binder. In this case, for example, a fluororesin can be used as the binder. As the fluororesin, polyvinylidene fluoride (PVDF) polytetrafluoroethylene (PTFE) or tetrafluoroethylene-hexafluoropropylene copolymer (FEP) may be used. it can. As the binder, a polyacrylic acid derivative or a polyacrylonitrile derivative can also be used. The polyacrylic acid derivative and the polyacrylonitrile derivative are at least one selected from the group consisting of a methyl acrylate unit, an ethyl acrylate unit, a methyl methacrylate unit, and an ethyl methacrylate unit, in addition to the acrylic acid unit and the acrylonitrile unit, respectively. It is preferable to contain. Also, polyethylene or styrene-butadiene rubber can be used as the binder. As the binder, the above materials may be used alone, or two or more materials may be used in combination. Among the above materials, a polymer containing an acrylonitrile unit, that is, a polyacrylonitrile derivative is particularly preferable. When such a material is used as a binder, the porous insulating layer can be made more flexible, so that cracks can be prevented from occurring in the porous insulating layer, and the porous insulating layer can be prevented from the positive or negative electrode. It can suppress that a layer peels.

  The porosity of the porous insulating layer is preferably 30 to 80%, more preferably 40 to 80%, and further preferably 50 to 80%. When a porous insulating layer having a porosity of 30% or more, particularly 40% or more is used, it is possible to suppress deterioration of charge / discharge characteristics when a large current is passed through the battery and charge / discharge characteristics in a low temperature environment. . However, if the porosity exceeds 80%, the mechanical strength of the porous insulating layer becomes weak, which is not preferable.

When carbon fibers are provided as a structure holding member in the mixture layer of the positive electrode, examples of the carbon fibers include vapor grown carbon fibers (VGCF), carbon fibers, and carbon nanotubes. Since vapor grown carbon fiber generally forms an aggregate, this aggregate is used as a structure holding member. This agglomerate is an agglomeration of vapor-grown carbon fibers having a fiber diameter of 0.01 to 5 μm, and some of the contacts where the vapor-grown carbon fibers are in contact with each other are made of a carbide of an organic compound such as tar or pitch. It is a flock-like or string-like structure that is chemically bonded and fixed and has a diameter of 5 to 500 μm, and fine cavities of various sizes are formed inside the aggregate. Such agglomerates can be produced using either of the following two production methods. In the first production method, first, a vapor-grown carbon fiber having a fiber diameter of 0.05 to 5 μm is compressed into a molded body having a bulk density of 0.02 g / cm ³ or more, and then, The molded body is heated at 600 ° C., preferably 800 ° C. or higher, and further mechanically crushed. In the second production method, vapor-grown carbon fiber is heated at 600 ° C. or higher, preferably 800 ° C. or higher while being compressed at a pressure of 0.1 kg / cm ² or higher, and further pulverized (Japanese Patent Laid-Open No. 9-132646). See the publication). The vapor-grown carbon fiber is not particularly limited, and may be a single fiber having no branch, a fiber having a branch, or a mixture of a single fiber and a fiber having a branch. Although it is good, it is preferable that it is a crude fiber which is not heat-treated and remains as produced. About 5 to 20% by weight of tar or pitch is adsorbed on the crude carbon fiber, and tar or pitch functions as a binder for bonding between carbon fibers when the carbon fibers are compressed, and is heated. Then, it carbonizes easily and adhere | attaches carbon fibers. If the vapor-grown carbon fiber after heat treatment is used, it is desirable to form by adding pitch or the like.

  Such carbon fibers are preferably provided also in the active material layer of the negative electrode as described above.

  Below, the structure of a positive electrode, a negative electrode, and a nonaqueous electrolyte is shown in order.

  As described above, in the positive electrode, a mixture layer is provided on both sides or one side of the current collector of the positive electrode, and the positive electrode mixture layer has an active material capable of electrochemically occluding and releasing at least lithium ions. And a positive electrode active material, a binder, a conductive agent, and a structure holding member.

The active material capable of electrochemically occluding and releasing lithium ions is an oxide, phosphate, sulfate, or silicate containing a metal element other than lithium and lithium, and other metal other than lithium. One or more elements may be used. Examples of the active material capable of electrochemically occluding and releasing lithium ions include lithium cobaltate (LiCoO ₂ ), modified lithium cobaltate, lithium nickelate (LiNiO ₂ ), modified lithium nickelate, lithium manganate (LiMn ₂ O ₂ ), a modified product of lithium manganate, a lithium iron phosphate (LiFePO ₄ ), a modified product of lithium iron phosphate, a lithium manganese phosphate (LiMnPO ₄ ), a modified product of lithium manganese phosphate, or It is preferable to use lithium iron sulfate (LiFeSO ₄ ). Further, as the active material of the positive electrode, a material obtained by substituting a part of Co, Ni, Mn or Fe in the above compound with another transition metal element or a typical metal element (for example, aluminum or magnesium) may be used. .

The binder for the positive electrode is not particularly limited, and polytetrafluoroethylene (PTFE), a modified PTFE, a modified PVDF, a modified PVDF, or modified acrylonitrile rubber particles can be used. When PTFE or a modified acrylonitrile rubber particle binder (for example, BM-500B manufactured by Nippon Zeon Co., Ltd.) is used as the binder, carboxymethylcellulose (CMC), polyethylene oxide (PEO; polyethylene oxide) or a modified acrylonitrile rubber is preferably used in combination.

  As the conductive agent for the positive electrode, acetylene black, ketjen black, or various graphites can be used. These may be used alone or in combination of two or more.

  The positive electrode current collector preferably contains a stable metal that does not decompose or melt even when a positive electrode potential is applied. For example, an aluminum foil or a film in which a metal such as aluminum is provided on the film surface is used. Can be used. Irregularities may be provided on the surface of the current collector, or the current collector may be perforated.

  In the negative electrode, as described above, the negative electrode active material layer is provided on both sides or one side of the negative electrode current collector. The negative electrode active material layer may contain a negative electrode active material and a binder, may further contain a thickener, and may further contain a structure holding member.

  The negative electrode active material can be used without limitation as long as it is a material capable of electrochemically occluding and releasing lithium ions. Specifically, various natural graphites, various artificial graphites, petroleum Carbon materials such as coke, carbon fiber, and fired organic polymer, metal oxide, silicon, silicon-containing composite material (material containing silicon and at least one element other than silicon), tin-containing composite material (other than tin and tin) A material containing at least one kind of element), various metals, alloys, and the like.

  The binder for the negative electrode is not particularly limited, but rubber particles are preferably used because they can exhibit excellent binding properties in a small amount, and those containing a styrene group and a butadiene group are particularly preferable. As the binder, for example, a styrene-butadiene copolymer (SBR) or a modified SBR can be used. When rubber particles are used as the binder for the negative electrode, it is desirable to use a thickener composed of a water-soluble polymer. As the water-soluble polymer, a cellulose resin is preferable, and CMC is particularly preferable. The amount of the binder and the thickener in the negative electrode active material layer is preferably 0.1 to 5 parts by weight per 100 parts by weight of the negative electrode active material. Further, PVDF or a modified PVDF can be used as the binder.

  Alternatively, in the negative electrode, the active material may be deposited on the surface of the negative electrode current collector by vapor deposition or the like.

  The negative electrode current collector preferably contains a stable metal that does not decompose or melt even when a negative electrode potential is applied. For example, a film in which a metal such as copper foil or copper is provided on the film surface is used. Can be used. Irregularities may be provided on the surface of the current collector, or the current collector may be perforated.

  As the nonaqueous electrolyte, a lithium salt dissolved in an organic nonaqueous solvent is used. The concentration of the lithium salt is generally 0.5 to 2 mol / L.

The lithium salt is not particularly limited, but for example, lithium hexafluorophosphate (LiPF ₆ ), lithium perchlorate (LiClO ₄ ), lithium borofluoride (LiBF ₄ ), or the like is preferably used. As the lithium salt, one of these may be used alone, or two or more of these may be used in combination.

Although it does not specifically limit as an organic nonaqueous solvent, For example, ethylene carbonate (EC; ethylene carbonate), propylene carbonate (PC; propylene carbonate), dimethyl carbonate (DMC; dimethyl carbonate), diethyl carbonate (DEC; diethyl carbonate) Or carbonates such as ethyl methyl carbonate (EMC); carboxylic acid esters such as γ-butyrolactone, γ-valerolactone, methyl formate, methyl acetate or methyl propionate; ethers such as dimethyl ether, diethyl ether or tetrahydrofuran, etc. Is used. As the organic non-aqueous solvent, one of the above may be used alone, or two or more may be used in combination. Among these, it is particularly preferable to use a carbonate ester.

Further, in order to form a good film on the electrode and to ensure the stability during overcharge, vinylene carbonate (VC), cyclohexylbenzene (CHB) or a modified product of VC or CHB is used. It is preferable to add to the non-aqueous electrolyte.

  In the present embodiment, the positive electrode mixture layer preferably includes ceramic particles or carbon fibers as the structure holding member. However, both the ceramic particles and the carbon fibers may be included. good.

  Further, although the configuration of the electrode group is not mentioned, in the electrode group according to the present embodiment, the positive electrode and the negative electrode may be wound through the porous insulating layer, or the electrode group according to the present embodiment may be wound through the porous insulating layer. The positive electrode and the negative electrode may be laminated. When the positive electrode and the negative electrode are wound, the shape of the end face of the electrode group may be a circle or a flat circle. When producing such an electrode group, the porous insulating layer may be laminated or wound with the positive electrode and the negative electrode interposed therebetween, or a paste containing the material of the porous insulating layer may be applied to the surface of the positive electrode or the negative electrode. It may be wound or laminated after being applied and the paste dried.

  Furthermore, although the form of the non-aqueous electrolyte was mentioned as an example of electrolyte, it cannot be overemphasized that the same effect is exhibited even if it is a gel-like electrolyte.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, the content described here is only the illustration of this invention, and this invention is not limited to these.

(I) Preparation of ceramic particles containing polycrystalline particles Here, ceramic particles containing α-alumina were prepared.

  First, aluminum tributoxide (aluminum alkoxide) was prepared. Aluminum tributoxide was hydrolyzed by adding pure water to produce an alumina gel and dried. This alumina gel was used as a ceramic precursor.

  Next, the alumina gel (ceramic precursor) was fired at 1200 ° C. for 3 hours to obtain an α-alumina fired body (ceramic fired body). When the SEM (scanning electron microscope) photograph of the obtained α-alumina fired body was taken and the average particle size of the nucleus composed of the single crystal of α-alumina was determined, the average particle size was about 0.2 μm. .

The obtained fired α-alumina was pulverized with a jet mill. Here, the crushing conditions were controlled so that the bulk density of the ceramic particles was 0.05 to 1.1 g / cm ³ and the BET specific surface area was ³ to 22 m ² / g.

In addition, the bulk density of α-alumina was measured by a stationary method using “Powder Tester (trade name)” manufactured by Hosokawa Micron Co., Ltd., and the BET ratio of α-alumina was measured using a BET (Brunauer-Emmett-Teller) method. The surface area was measured. Moreover, when the obtained particle | grains were observed with the SEM photograph, it was confirmed that all are dendritic polycrystalline particles.
(II) Preparation of slurry containing raw material of porous insulating layer 4 parts by weight of polyacrylic acid derivative (“BM-720H (trade name) manufactured by Nippon Zeon Co., Ltd.) with respect to 100 parts by weight of predetermined polycrystalline alumina particles ”, A binder) and an appropriate amount of N-methyl-2-pyrrolidone (hereinafter, NMP; N-methylpyrrolidone, dispersion medium) were mixed to prepare a slurry having a nonvolatile content of 60% by weight.

Here, the mixture of the polycrystalline alumina particles, the binder, and the dispersion medium is stirred in a medialess disperser “CLEAMIX (trade name)” manufactured by M Technique Co., Ltd., and the polycrystalline alumina particles, the binder, Was dispersed in NMP until uniform, to obtain a slurry.
<a> Production of Positive Electrode 3 kg of lithium cobalt oxide (positive electrode active material) and 1 kg of “# 1320 (trade name)” (NMP solution containing 12% by weight of PVDF, positive electrode binder) manufactured by Kureha Chemical Co., Ltd. Then, 90 g of acetylene black (conductive agent), 60 g of VGCF (structure holding member) manufactured by Showa Denko KK, and an appropriate amount of NMP are stirred in a double-arm kneader to prepare a positive electrode mixture paint did. Prepare an aluminum foil (positive electrode current collector) with a thickness of 15 μm, and apply the positive electrode mixture paint to a portion of the aluminum foil other than the portion where the positive electrode lead is connected (positive electrode lead connecting portion). Formed. When the coating film was dried, the dried coating film was rolled using a roller. Thereby, the mixture layer of the positive electrode was formed on the aluminum foil, and the density of the active material (= weight of the active material / volume of the mixture layer) was 3.3 g / cm ³ . At this time, the total of the thickness of the aluminum foil and the thickness of the mixture layer of the positive electrode (the thickness of the positive electrode) was 160 μm. Thereafter, the positive electrode was cut to a width that could be inserted into a battery can of a cylindrical battery (Part No. 18650) to obtain a positive electrode hoop.
<B> Production of Negative Electrode 3 kg of artificial graphite (negative electrode active material) and “BM-400B (trade name)” manufactured by Nippon Zeon Co., Ltd. (an aqueous dispersion containing 40% by weight of a modified styrene-butadiene copolymer) Liquid, binder) 75 g, CMC (thickener) 30 g, and an appropriate amount of water were stirred in a double-arm kneader to prepare a negative electrode mixture paint. A copper foil having a thickness of 10 μm was prepared, and a coating film was formed by applying a negative electrode mixture paint to a portion of the copper foil other than a portion to which the negative electrode lead was connected (negative electrode lead connecting portion). When the coating film was dried, the dried coating film was rolled using a roller. Thereby, the active material layer of the negative electrode was formed on the copper foil, and the density of the active material (= weight of active material / volume of active material layer) was 1.4 g / cm ³ . Under the present circumstances, the sum total (thickness of a negative electrode) of the thickness of copper foil and the active material layer of a negative electrode was controlled to 180 micrometers. Thereafter, the negative electrode was cut into a width that could be inserted into a battery can of a cylindrical battery (Part No. 18650) to obtain a negative electrode hoop.
<C> Formation of Porous Insulating Layer A slurry containing the raw material for the porous insulating layer was applied to both surfaces of the negative electrode hoop using a gravure roll method at a speed of 0.5 m / min. Thereafter, hot air at 120 ° C. was applied to the slurry at an air flow rate of 0.5 m / sec and dried. As a result, porous insulating layers having a thickness of 20 μm were formed on both sides of the negative electrode.
<D> Preparation of Nonaqueous Electrolyte Solution A nonaqueous electrolyte solution is prepared by dissolving LiPF ₆ at a concentration of 1 mol / L in a mixture of nonaqueous solvents containing EC, DMC, and EMC at a volume ratio of 2: 3: 3. did. Moreover, VC was added so that it might become 2 weight part per 100 weight part of non-aqueous electrolyte.
<E> Production of Battery A cylindrical battery of product number 18650 was produced in the following manner using the above-described positive electrode, negative electrode, and non-aqueous electrolyte. In addition, in FIG. 3, the schematic longitudinal cross-sectional view of a nonaqueous electrolyte secondary battery is shown.

  First, the positive electrode hoop and the negative electrode hoop in which the porous insulating layer was formed on both surfaces were each cut into a predetermined length. This produced the positive electrode plate 1 and the negative electrode plate 2 in which the porous insulating layer 3 was formed on both surfaces.

  Next, one end of the positive electrode lead 5 was resistance welded to the connection portion of the positive electrode lead, and one end of the negative electrode lead 6 was resistance welded to the connection portion of the negative electrode lead. Thereafter, the positive electrode plate 1 and the negative electrode plate 2 are arranged so that the porous insulating layer 3 is sandwiched between the positive electrode plate 1 and the negative electrode plate 2, and the positive electrode plate 1 and the negative electrode plate 2 are wound to form the cylindrical electrode group 4. Configured. Here, in the electrode group 4, the thickness of the porous insulating layer 3 was 20 μm.

  After passing the negative electrode lead 6 through the lower insulating ring 10, the electrode group 4 was accommodated in a metal bottomed case (battery case) 7. Subsequently, the negative electrode lead 6 was resistance-welded to the bottom of the bottomed case 7 made of metal, and the negative electrode lead 6 and the bottomed case 7 were electrically connected. Then, the upper insulating ring 9 was disposed on the upper end surface of the electrode group 4, and the positive lead 5 was passed through the upper insulating ring 9, and then a seat was formed near the open end of the bottomed case 7 made of metal.

  Subsequently, the positive electrode lead 5 was laser welded to the metal filter 8a of the sealing plate 8 to which the resin outer gasket 11 was attached, and the positive electrode lead 5 and the sealing plate 8 were electrically connected. Then, a non-aqueous electrolyte was injected from the open end of the bottomed case 7 made of metal, the pressure was reduced to 133 Pa, and the electrode group 4 was impregnated with the non-aqueous electrolyte.

  Then, the open end of the bottomed case 7 was sealed by bending the positive electrode lead 5 and attaching the sealing plate 8 to which the resin outer gasket 11 was attached to the seat of the bottomed case 7. In this way, a cylindrical nonaqueous electrolyte secondary battery A was manufactured.

  A nonaqueous electrolyte secondary battery B was produced in the same manner as in Example 1 except that VGCF was added as a structure holding member to the negative electrode active material layer. Specifically, 60 g of VGCF manufactured by Showa Denko KK was added to the negative electrode mixture paint of Example 1 to prepare the negative electrode mixture paint of Example 2.

  A nonaqueous electrolyte secondary battery C was produced in the same manner as in Example 1 except that ceramic particles containing polycrystalline particles were used instead of VGCF as the structure holding member in the positive electrode mixture layer. Specifically, instead of adding 60 g of VGCF manufactured by Showa Denko KK, 60 g of ceramic particles produced in “(I) Preparation of ceramic particles containing polycrystalline particles” in Example 1 were added, and Example 3 was added. A positive electrode mixture paint was prepared.

As the raw material for the porous insulating layer, the same procedure as in Example 1 was used, except that alumina particles made of spherical or nearly spherical primary particles having an average particle diameter of 0.3 μm were used instead of dendritic polycrystalline particles. Thus, a non-aqueous electrolyte secondary battery D was produced.
(Comparative Example 1)
The non-aqueous electrolyte 2 is the same as in Example 1 except that no structure holding member is provided in the positive electrode mixture layer and that a microporous film (separator) made of polyethylene resin is used instead of the porous insulating layer. A secondary battery E was produced. A method for manufacturing the battery is described below.
<E> Production of Battery A cylindrical battery having a product number of 18650 was produced in the following manner using the above-described positive electrode, negative electrode, and non-aqueous electrolyte.

  First, the positive electrode and the negative electrode were each cut to a predetermined length. Then, one end of the positive electrode lead was connected to the connection portion of the positive electrode lead, and one end of the negative electrode lead was connected to the connection portion of the negative electrode lead.

  Next, the positive electrode and the negative electrode were wound through a microporous film made of polyethylene resin having a thickness of 20 μm to form a cylindrical electrode group.

Thereafter, in the same manner as in Example 1, a nonaqueous electrolyte secondary battery E was produced.
(Comparative Example 2)
A nonaqueous electrolyte secondary battery F was produced in the same manner as in Comparative Example 1 except that VGCF was provided as a structure holding member on the active material layer of the negative electrode. That is, the negative electrode of Example 2 was used as the negative electrode.
(Comparative Example 3)
A nonaqueous electrolyte secondary battery G was produced in the same manner as in Comparative Example 1 except that VGCF was provided as a structure holding member in the positive electrode mixture layer. That is, the positive electrode of Example 1 was used as the positive electrode. (Comparative Example 4)
A non-aqueous electrolyte secondary battery in the same manner as in Example 1 except that no structure holding member is provided in the positive electrode mixture layer, that is, VGCF (structure holding member) manufactured by Showa Denko KK is not provided in the positive electrode. H was produced. That is, the positive electrode of Comparative Example 1 was used as the positive electrode.

Si was used instead of artificial graphite as the negative electrode active material, a porous insulating layer was provided on both sides of the positive electrode instead of both sides of the negative electrode, and a non-aqueous electrolyte was prepared without adding VC A nonaqueous electrolyte secondary battery I was produced in the same manner as Example 1 except for the above. Specifically, a negative electrode, a porous insulating layer, and a battery were produced according to the following method.
<B> Production of Negative Electrode A simple Si ingot (manufactured by High Purity Chemical Co., Ltd. has a purity of 99.999% and an average particle size of 5 to 35 mm) was placed in a graphite crucible. This crucible is put in a vacuum deposition apparatus, and vacuum deposition (acceleration voltage: −8 kV, current: 150 mA, vacuum) by an electron beam is applied to an electrolytic Cu foil (Furukawa Circuit Foil, thickness: 20 μm, negative electrode current collector). Degree; 3 × 10 ⁻⁵ Torr). When the deposition of Si was completed on one side of the electrolytic Cu foil, vacuum deposition was similarly performed on the other side (non-deposited surface) of the electrolytic Cu foil. This formed the negative electrode active material layer on both surfaces of the electrolytic Cu foil. Thereafter, the electrode plate was slit to a width that could be inserted into a battery can of a cylindrical battery (Part No. 18650) to obtain a negative electrode hoop.
<C> Formation of Porous Insulating Layer A slurry containing the raw material for the porous insulating layer was applied to both surfaces of the positive electrode hoop using a gravure roll method at a speed of 0.5 m / min. Thereafter, hot air at 120 ° C. was applied to the slurry at an air flow rate of 0.5 m / sec and dried. As a result, porous insulating layers having a thickness of 20 μm were formed on both sides of the positive electrode.
(Comparative Example 5)
A nonaqueous electrolyte secondary battery J was produced in the same manner as in Example 5 except that a microporous film made of polyethylene resin was used instead of the porous insulating layer. Specifically, a positive electrode was produced in the same manner as in Example 1, a negative electrode was produced in the same manner as in Example 5, and a battery was produced in the same manner as in Comparative Example 1.

A nonaqueous electrolyte secondary battery K was prepared in the same manner as in Example 2 except that a microporous membrane having alumina particles present in a polyethylene resin microporous membrane was used instead of the porous insulating layer in Example 2. Produced. A microporous membrane in which alumina particles were present in a polyethylene resin microporous membrane was prepared using the method described in JP-A-2005-71979. A method for manufacturing the battery is described below.
<E> Production of Battery A cylindrical battery having a product number of 18650 was produced in the following manner using the above-described positive electrode, negative electrode, and non-aqueous electrolyte. First, the positive electrode and the negative electrode were each cut to a predetermined length. Then, one end of the positive electrode lead was connected to the connection portion of the positive electrode lead, and one end of the negative electrode lead was connected to the connection portion of the negative electrode lead. Next, the positive electrode and the negative electrode were wound through a microporous membrane in which ceramic particles were present in a microporous membrane made of polyethylene resin having a thickness of 20 μm to constitute a cylindrical electrode plate group. Thereafter, a nonaqueous electrolyte secondary battery K was produced in the same manner as in Example 1.

  Next, using the nonaqueous electrolyte secondary batteries A to D, I and K according to the example and the nonaqueous electrolyte secondary batteries E to H and J according to the comparative example, the number of cycles is measured according to the following method. did.

  Each battery was preliminarily charged / discharged twice and stored in a charged state in a 45 ° C. environment for 7 days. Then, the following charging / discharging cycle was performed in a 20 degreeC environment.

<Cycle conditions>
The battery was charged with a current of 1000 mA until the voltage reached 4.2 V (constant current charging), and then left for 1 minute. Subsequently, a current of 1000 mA was applied to discharge until the voltage reached 3.0 V (constant current discharge), and then left for 1 minute.

  The measurement results of the cycle number are shown in Table 1. The “cycle number” in Table 1 indicates the cycle number when the discharge capacity falls below 80% of the initial discharge capacity.

  Considering the nonaqueous electrolyte secondary batteries A to H and K, in the nonaqueous electrolyte secondary batteries A to D and K according to the example, the number of cycles is larger than that of the nonaqueous electrolyte secondary batteries E to H according to the comparative example. increased. Hereinafter, the nonaqueous electrolyte secondary batteries E to H according to the comparative example will be considered, and then the nonaqueous electrolyte secondary batteries A to D and K according to the examples will be considered.

  In the non-aqueous electrolyte secondary battery F of Comparative Example 2, the number of cycles was larger than that of the non-aqueous electrolyte secondary battery E (Comparative Example 1) because the structure holding member was provided in the active material layer of the negative electrode. However, the effect (the rate of increase in the number of cycles) was small compared to the nonaqueous electrolyte secondary batteries A to D and K according to the examples. Similarly, in the nonaqueous electrolyte secondary battery G of Comparative Example 3, a structure holding member is provided in the positive electrode mixture layer, and in the nonaqueous electrolyte secondary battery H of Comparative Example 4, the structure is provided in the porous insulating layer. Since the holding member was provided, the number of cycles was larger than that of the nonaqueous electrolyte secondary battery E. However, the effect was small compared with the non-aqueous electrolyte secondary batteries A to D and K according to the examples. The reason is that when the non-aqueous electrolyte secondary battery is charged and discharged, the positive electrode active material and the porous insulating layer do not expand or contract, or hardly expand or contract, but the negative electrode active material and the positive electrode active material and This is because it expands or contracts more than the porous insulating layer.

  The reason why the number of cycles is small in the nonaqueous electrolyte secondary batteries E to H is considered as follows.

  When the active material of the negative electrode expands in the nonaqueous electrolyte secondary battery E, the positive electrode and the separator are compressed, so that the pores existing in the positive electrode and the separator are crushed. As a result, the non-aqueous electrolyte is pushed out from the holes.

  In the nonaqueous electrolyte secondary battery F, the structure holding member suppresses the expansion of the negative electrode active material, but it is difficult to sufficiently suppress the expansion of the negative electrode active material. Therefore, when the active material of the negative electrode expands, the positive electrode and the separator are compressed, and as a result, the nonaqueous electrolytic solution is pushed out from the mixture layer and the separator of the positive electrode.

  In the nonaqueous electrolyte secondary battery G, the structure holding member is provided in the positive electrode mixture layer, but when the active material of the negative electrode expands, the separator is compressed, so that the nonaqueous electrolyte is pushed out of the separator.

  Similarly, in the nonaqueous electrolyte secondary battery H, a porous insulating layer is provided instead of the separator, and a structure holding member is provided in the porous insulating layer. However, the structure holding member is not provided in the positive electrode mixture layer. Therefore, when the active material of the negative electrode expands, the positive electrode is compressed, and as a result, the nonaqueous electrolytic solution is pushed out from the mixture layer of the positive electrode.

  On the other hand, in the nonaqueous electrolyte secondary batteries A to D and K according to the examples, the structure holding member is provided in both the positive electrode mixture layer and the porous insulating layer. Therefore, even if the active material of the negative electrode is about to expand, the structure holding member suppresses expansion of the active material of the negative electrode (particularly, expansion of the active material of the negative electrode in the thickness direction of the active material layer of the negative electrode). Therefore, it can suppress that a non-aqueous electrolyte is extruded from the mixture layer of a positive electrode, the porous insulating layer, and the active material layer of a negative electrode. Therefore, the number of cycles can be increased and the cycle characteristics can be improved.

  Further, when comparing the non-aqueous electrolyte secondary battery A of Example 1 and the non-aqueous electrolyte secondary battery D of Example 4, it is preferable to use ceramic particles having a dendritic shape as the structure holding member. The number of cycles increased compared to using ceramic particles having a spherical shape. The reason for this is that the ceramic particles having a dendritic shape are more likely to be entangled with each other than the ceramic particles having a spherical shape, so that the strength of the structure holding member can be increased. I think there is.

  Next, when comparing the non-aqueous electrolyte secondary battery I of Example 5 and the non-aqueous electrolyte secondary battery J of Comparative Example 5, the non-aqueous electrolyte secondary battery I is more than the non-aqueous electrolyte secondary battery J. The number of cycles has increased. When an alloy or a metal oxide is used as the active material for the negative electrode, the capacity can be increased, but the expansion coefficient is higher than when carbon is used as the active material for the negative electrode. Therefore, when a polyethylene resin separator is used instead of the porous insulating layer as in the non-aqueous electrolyte secondary battery J, the number of cycles is greatly reduced. On the other hand, in the nonaqueous electrolyte secondary battery I, since the structure holding member is provided in both the positive electrode mixture layer and the porous insulating layer, even if the negative electrode active material is expanded, the structure holding member is Suppresses compression of the porous insulating layer. Therefore, it was possible to suppress the non-aqueous electrolyte from being pushed out of the positive electrode mixture layer, the porous insulating layer, and the negative electrode active material layer, and the number of cycles was increased.

  As mentioned above, the nonaqueous electrolyte secondary battery excellent in cycling characteristics was able to be provided by adopting the composition concerning Examples 1-6.

  The present invention is applied to small-sized consumer applications such as notebook computers or mobile phones, and large-scale applications that require long-term durability such as power storage, electric vehicles, and hybrid electric vehicles.

(A)-(c) is the figure which showed typically the compressive force which generate | occur | produces with the expansion of the active material of a negative electrode at the time of charge. (A) shows the case where the structure holding member and the inhibitor are not provided, (b) shows the case where only the inhibitor is provided in the active material layer of the negative electrode, and (c) shows the structure retention. The case where the member is provided in both the mixture layer and the porous insulating layer of the positive electrode is shown. It is a photograph of the scanning electron microscope of the ceramic particle whose shape is dendritic. It is a schematic longitudinal cross-sectional view of a nonaqueous electrolyte secondary battery.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Positive electrode plate 2 Negative electrode plate 3 Porous insulating layer 4 Electrode plate group 5 Positive electrode lead 6 Negative electrode lead 7 Bottomed case 8 Sealing plate 8a Filter 11 Outer gasket 21 Dendritic ceramic polycrystal particle A Active material N of negative electrode Active of negative electrode Material layer (negative electrode layer)
P Positive electrode mixture layer

Claims (8)

A positive electrode having a mixture layer containing an active material capable of electrochemically occluding and releasing lithium ions;
A negative electrode having a layer containing an active material capable of electrochemically occluding and releasing lithium ions;
A porous insulating layer disposed between the positive electrode and the negative electrode;
A non-aqueous electrolyte held in at least the porous insulating layer,
The mixture layer of the positive electrode includes a structure holding member,
The porous insulating layer is a non-aqueous electrolyte secondary battery including the structure holding member or made of the structure holding member.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the structure holding member suppresses expansion of the active material of the negative electrode in a thickness direction of the layer of the negative electrode.   The nonaqueous electrolyte secondary battery according to claim 1, wherein the structure holding member present in the porous insulating layer is ceramic particles.   The nonaqueous electrolyte secondary battery according to claim 3, wherein the ceramic particles have a dendritic shape.   The nonaqueous electrolyte secondary battery according to claim 1, wherein the structure holding member present in the mixture layer of the positive electrode is a dendritic ceramic particle.   The nonaqueous electrolyte secondary battery according to claim 1, wherein the structure holding member present in the mixture layer of the positive electrode is a carbon fiber.   The nonaqueous electrolyte secondary battery according to claim 1, wherein the structure holding member is also included in the layer of the negative electrode.   The non-aqueous electrolyte secondary battery according to claim 7, wherein the structure holding member present in the layer of the negative electrode is a carbon fiber.

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