JP6601065B2 - Secondary battery - Google Patents

Description

  The present invention relates to a secondary battery, and more particularly to a secondary battery in which the occurrence of problems that may occur due to electrode burrs coming into contact with a counter electrode is prevented and the reliability is further improved.

  Lithium ion secondary batteries are characterized by their small size and large capacity, are widely used as power sources for electronic devices such as mobile phones and notebook computers, and have contributed to improving the convenience of portable IT devices. In recent years, the use in a larger application such as a power source for driving a motorcycle or an automobile or a storage battery for a smart grid has attracted attention. As demand for lithium-ion secondary batteries increases and it is used in various fields, it is possible to use batteries with higher energy density, life characteristics that can withstand long-term use, and a wide range of temperature conditions. Such characteristics are required.

  Although details will be described later with reference to the drawings, in the case of a laminated secondary battery in which positive electrodes and negative electrodes are alternately stacked via separators, when manufacturing electrodes (for example, a slitting process or a punching process, details will be described later). ) May cause burr. Patent Document 1 discloses that an insulating layer is provided at a location where burrs are likely to occur in order to solve the problem of shorts caused by burrs that occur near the current collecting tab (narrow portion) of the electrode.

JP2015-72758A

  By the way, the problem of short due to burrs is a problem that may occur not only near the current collecting tab but also at the side edge of the electrode, and it is desirable that the short circuit does not occur at the side edge of the electrode.

  Accordingly, an object of the present invention is to provide a secondary battery in which the occurrence of problems that may occur due to electrode burrs coming into contact with a counter electrode is prevented and the reliability is further improved.

In order to achieve the above object, a battery according to an embodiment of the present invention is as follows:
A first electrode having a first metal foil and a first active material layer formed on the metal foil;
A second metal foil and a second active material layer formed on the metal foil, wherein an area of the second active material layer is larger than an area of the first active material layer in a plan view; A large second electrode having a different polarity from the first electrode;
An insulating layer formed on the first electrode so as to be interposed between both electrodes;
With
The first electrode has a region where the first active material layer is formed on the first metal foil and a region other than the electrical connection portion where the active material layer is not formed. ,
When the cut surface of the laminate is viewed, the end of the first metal foil extends outside the end of the second metal foil, and
The insulating layer is formed on the first active material layer, and in a region where the active material is not formed, the insulating layer is formed to a position that is at least outside the end portion of the second electrode. A secondary battery characterized by that.

  ADVANTAGE OF THE INVENTION According to this invention, the generation | occurrence | production of the problem which may arise when the burr | flash of an electrode contacts a counter electrode can be prevented, and the secondary battery which improved reliability more can be provided.

It is a perspective view which shows the basic structure of a film-clad battery. It is a disassembled perspective view which shows the basic structure of a film-clad battery. It is sectional drawing which shows the cross section of the battery of FIG. 1 typically. It is a figure for demonstrating the structure of a positive electrode. It is sectional drawing for demonstrating the edge part structure of a laminated body. It is sectional drawing for demonstrating the edge part structure (modification) of a laminated body. It is sectional drawing for demonstrating the problem which may arise with the conventional structure. It is sectional drawing which shows the other aspect of a laminated body. It is a figure which shows the location which can provide the edge part structure which concerns on this invention. It is a schematic diagram which shows the procedure of electrode preparation (coating). It is a schematic diagram which shows the procedure of electrode preparation (slit). It is a schematic diagram which shows the procedure of electrode preparation (punching).

1. Basic structure of film-clad battery The structure of a film-clad battery will be described with reference to FIGS. As will be described later, the features of one embodiment of the present invention are the insulating layer disposed between the positive electrode and the negative electrode, the shape and positional relationship of the positive electrode end portion and the negative electrode end portion, etc. In FIG. 3, those illustrations are omitted, and the basic configuration of the battery will be described first.

  A film-clad battery 1 according to an embodiment of the present invention includes a battery element 20 configured as a laminate, a film-clad body 10 that accommodates the battery element 20 together with an electrolyte, a positive electrode tab 51 and a negative electrode tab 52 (hereinafter referred to as these). Lithium ion secondary battery.

  In the battery element 20, a plurality of positive electrodes 30 and a plurality of negative electrodes 40 are alternately stacked with separators 25 (which may be omitted) interposed therebetween. In the positive electrode 30, the positive electrode active material layer 32 is formed on both surfaces of the positive electrode metal foil 31. Similarly, in the negative electrode 40, the negative electrode active material layer 42 is formed on both surfaces of the negative electrode metal foil 41. Although the overall external shape of the battery element 20 is not particularly limited, in this example, it is a flat and substantially rectangular parallelepiped.

  Although not shown in detail, each of the positive electrode 30 and the negative electrode 40 has an extension part that partially protrudes from a part of the outer periphery, and this is a tab part for electrical connection. The extension part of the positive electrode 30 and the extension part of the negative electrode 40 are alternately arranged so as not to interfere with each other when the positive electrode and the negative electrode are stacked. All the negative electrode extensions are gathered together and connected to the negative electrode tab 52. Similarly, for the positive electrode, all the positive electrode extensions are gathered together and connected to the positive electrode tab 51 ( (See FIGS. 2 and 3).

  Note that the portions gathered together in the stacking direction between the extension portions in this way are also called “current collectors” or the like. For the connection between the current collector and the electrode tab, resistance welding, ultrasonic welding, laser welding, caulking, adhesion with a conductive adhesive, or the like can be employed.

  Various materials can be adopted as the electrode tab. As an example, the positive electrode tab 51 is aluminum or an aluminum alloy, and the negative electrode tab 52 is copper or nickel. When the material of the negative electrode tab 52 is copper, nickel may be arranged on the surface. Each of the electrode tabs 51 and 52 is electrically connected to the battery element 20 and is drawn out of the film exterior body 10.

2. Configuration of each part [Separator]
In the present embodiment, the separator can be omitted, but when provided, the following can be used. As the separator, for example, an aramid, polyimide, polyester, cellulose, polyolefin resin such as polyethylene or polypropylene can be used. A polyolefin resin that is crosslinked by electron beam irradiation or addition of a crosslinking agent to increase the melting point may be used. Moreover, any structure, such as a woven fabric, a nonwoven fabric, or a microporous film, may be used.

  The separator preferably has heat resistance. Specifically, it is preferable that the melting point at which melting or softening occurs and the temperature at which 3% thermal shrinkage is not 200 ° C. or lower. When the separator melts, the gap of the separator becomes small, and the ionic conductivity of the electrolytic solution can be maintained. Furthermore, if the separator is completely melted, the insulation between the electrodes cannot be maintained. Further, when the separator contracts, the insulation between the electrodes cannot be maintained. This shrinkage is preferably 5% or less at 200 ° C., more preferably 3% or less.

  The melting point of the separator can be confirmed with a scanning calorimeter (DSC), a viscoelasticity measuring device (DMA) or the like. If the linear expansion coefficient measuring device (TMA) is used, not only the melting point but also the 3% shrinkage temperature. Can also be measured.

  In particular, the separator is preferably one that does not deform and shrink to a temperature that is 50 ° C. or higher, 100 ° C. or higher, or 200 ° C. or higher higher than the melting point of the heat-sealing layer of the laminate film. The form of the separator may be a web or a sheet. The above items can be used alone or in combination.

As the separator, a separator made of an inorganic material such as ceramic or glass can also be used. As the inorganic separator, a nonwoven fabric separator made of ceramic short fibers such as alumina, alumina-silica, and potassium titanate can be used. Or the separator which consists of a base material which consists of a textile fabric, a nonwoven fabric, paper, or a porous film, and a layer containing a heat resistant nitrogen-containing aromatic polymer and ceramic powder may be sufficient. Alternatively, a heat-resistant layer is provided on a part of the surface, and the heat-resistant layer is made of a porous thin film layer containing ceramic powder, a porous thin film layer of heat-resistant resin, or a composite of ceramic powder and heat-resistant resin. It may be a porous thin film layer separator. Alternatively, it may be a separator having a porous film layer in which secondary particles obtained by sintering or dissolving and recrystallizing a part of primary particles of a ceramic substance are bonded by a binder. Alternatively, it includes a porous film formed by bonding a ceramic material and a binder, and as the ceramic material, silica (SiO ₂ ), alumina (Al ₂ O ₃ ), zirconium oxide (ZrO ₂ ), titanium oxide (TiO ₂ ) ₂ ), a separator using silicon (Si) nitride, aluminum (Al) hydroxide, zirconium (Zr) alkoxide, or titanium (Ti) ketone compound. Alternatively, a separator including a polymer substrate and a ceramic-containing coating layer of Al ₂ O ₃ , MgO, TiO ₂ , Al (OH) ₃ , Mg (OH) ₂ , and Ti (OH) ₄ formed on the polymer substrate It may be.

[Negative electrode]
A negative electrode has the negative electrode metal foil formed with metal foil, and the negative electrode active material layer coated on both surfaces of the negative electrode metal foil. The negative electrode active material layer is bound so as to cover the negative electrode metal foil with a negative electrode binder. The negative electrode metal foil is formed to have an extension connected to the negative electrode terminal, and the negative electrode active material is not applied to the extension.

  The negative electrode active material in the present embodiment is not particularly limited. For example, a carbon material that can occlude and release lithium ions, a metal that can be alloyed with lithium, a metal oxide that can occlude and release lithium ions, and the like. Is mentioned.

  Examples of the carbon material include carbon, amorphous carbon, diamond-like carbon, carbon nanotube, or a composite thereof. Here, carbon with high crystallinity has high electrical conductivity, and is excellent in adhesion to a negative electrode metal foil made of a metal such as copper and voltage flatness. On the other hand, since amorphous carbon having low crystallinity has a relatively small volume expansion, it has a high effect of relaxing the volume expansion of the entire negative electrode, and deterioration due to non-uniformity such as crystal grain boundaries and defects hardly occurs.

  A negative electrode containing a metal or metal oxide is preferable in that the energy density can be improved and the capacity per unit weight or unit volume of the battery can be increased.

  Examples of the metal include Al, Si, Pb, Sn, In, Bi, Ag, Ba, Ca, Hg, Pd, Pt, Te, Zn, La, or alloys of two or more thereof. Moreover, you may use these metals or alloys in mixture of 2 or more types. 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, and composites thereof. In this embodiment, it is preferable that tin oxide or silicon oxide is included as a negative electrode active material, and it is more preferable that silicon oxide is included. This is because silicon oxide is relatively stable and hardly causes a reaction with other compounds. Moreover, 0.1-5 mass% of 1 type, or 2 or more types of elements chosen from nitrogen, boron, and sulfur can also be added to a metal oxide, for example. By carrying out like this, the electrical conductivity of a metal oxide can be improved.

  Further, the negative electrode active material can be used by mixing a plurality of materials without using a single material. For example, the same kind of materials such as graphite and amorphous carbon may be mixed, or different kinds of materials such as graphite and silicon may be mixed.

  The binder for the negative electrode is not particularly limited. For example, polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, styrene-butadiene copolymer. Rubber, polytetrafluoroethylene, polypropylene, polyethylene, polyimide, polyamideimide, polyacrylic acid, or the like can be used. Of these, polyimide or polyamideimide is preferred because of its high binding properties. The amount of the binder for the negative electrode used is 0.5 to 25 parts by mass with respect to 100 parts by mass of the negative electrode active material from the viewpoints of “sufficient binding force” and “higher energy” which are in a trade-off relationship. Is preferred.

  As the negative electrode metal foil, 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.

[Positive electrode]
The positive electrode is an electrode on the high potential side in the battery, and includes a positive electrode metal foil formed of a metal foil and a positive electrode active material coated on both surfaces of the positive electrode metal foil. The positive electrode active material is bound so as to cover the positive electrode metal foil with a positive electrode binder. The positive electrode metal foil is formed to have an extension connected to the positive electrode terminal, and the positive electrode active material is not applied to the extension.

The positive electrode active material is not particularly limited as long as it is a material capable of occluding and releasing lithium, but it is preferable to include a high-capacity compound from the viewpoint of increasing the energy density. Examples of the high-capacity compound include nickel-lithium oxide (LiNiO ₂ ) or lithium-nickel composite oxide obtained by substituting a part of nickel in nickel-lithium oxide with another metal element. The layered structure represented by the following formula (A) Lithium nickel composite oxide is preferred.

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 Ni content is high, that is, in the formula (A), x is preferably less than 0.5, and more preferably 0.4 or less. Examples of such compounds include Li _α Ni _β Co _γ Mn _δ O ₂ (0 <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, β + γ + δ = 1, β ≧ 0.7, γ ≦ 0.2) and the like, and in particular, LiNi _β Co _γ Mn _δ O ₂ (0.75 ≦ β ≦ 0.85, 0.05 ≦ γ ≦ 0.15, 0.10 ≦ δ ≦ 0.20). 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 can be preferably used 0.1 _{O 2} or the like.

From the viewpoint of thermal stability, it is also preferable that the Ni content does not exceed 0.5, that is, in the formula (A), x is 0.5 or more. It is also preferred that the number of specific transition metals does not exceed half. Examples of such compounds include Li _α Ni _β Co _γ Mn _δ O ₂ (0 <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%) Can also be included).

  In addition, two or more compounds represented by the formula (A) may be used as a mixture. For example, NCM532 or NCM523 and NCM433 may be used in a range of 9: 1 to 1: 9 (typically 2 It is also preferable to use a mixture in 1). Furthermore, 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. As a result, a battery having a high capacity and high thermal stability can be formed.

Other than the above, as the positive electrode active material, for example, 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 a part of these transition metals replaced with another metal; Li in these lithium transition metal oxides more than the stoichiometric composition And those having an olivine structure such as LiFePO ₄ . Furthermore, a material in which these metal oxides are partially substituted with Al, Fe, P, Ti, Si, Pb, Sn, In, Bi, Ag, Ba, Ca, Hg, Pd, Pt, Te, Zn, La, etc. Can also be used. Any of the positive electrode active materials described above can be used alone or in combination of two or more.

  A radical material or the like can also be used as the positive electrode active material.

  As the positive electrode binder, the same binder as the negative electrode binder can be used. The amount of the binder for the positive electrode to be used is preferably 2 to 15 parts by mass with respect to 100 parts by mass of the positive electrode active material from the viewpoints of “sufficient binding force” and “high energy” in a trade-off relationship. .

  As the positive electrode metal foil, the same as the negative electrode metal foil can be used.

  A conductive auxiliary material may be added to the coating layer of the positive electrode active material for the purpose of reducing impedance. Examples of the conductive auxiliary material include carbonaceous fine particles such as graphite, carbon black, and acetylene black.

[Electrolytes]
As the electrolyte, a nonaqueous electrolytic solution containing a lithium salt (supporting salt) and a nonaqueous solvent that dissolves the supporting salt can be used.

  As the non-aqueous solvent, an aprotic organic solvent such as a carbonic acid ester (chain or cyclic carbonate), a carboxylic acid ester (chain or cyclic carboxylic acid ester), or a phosphoric acid ester can be used.

  Examples of the carbonate solvent include cyclic carbonates such as propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), and vinylene carbonate (VC); dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate. (EMC), chain carbonates such as dipropyl carbonate (DPC); and propylene carbonate derivatives.

  Examples of the carboxylic acid ester solvent include aliphatic carboxylic acid esters such as methyl formate, methyl acetate, and ethyl propionate; and lactones such as γ-butyrolactone.

  Among these, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (MEC), dipropyl carbonate Carbonic acid esters (cyclic or chain carbonates) such as (DPC) are preferred.

  Examples of the phosphate ester include trimethyl phosphate, triethyl phosphate, tripropyl phosphate, trioctyl phosphate, and triphenyl phosphate.

  Other solvents that can be contained in the non-aqueous electrolyte include, for example, ethylene sulfite (ES), propane sultone (PS), butane sultone (BS), dioxathilane-2,2-dioxide (DD), and sulfolene. 3-methylsulfolene, sulfolane (SL), succinic anhydride (SUCAH), propionic anhydride, acetic anhydride, maleic anhydride, diallyl carbonate (DAC), dimethyl 2,5-dioxahexanoate, 2,5 -Dioxahexaneniate dimethyl, furan, 2,5-dimethylfuran, diphenyl disulfide (DPS), dimethoxyethane (DME), dimethoxymethane (DMM), diethoxyethane (DEE), ethoxymethoxyethane, chloroethylene carbonate , Dimethyl ether, methyl ether Ether, methyl propyl ether, ethyl propyl ether, dipropyl ether, methyl butyl ether, diethyl ether, phenyl methyl ether, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-MeTHF), tetrahydropyran (THP), 1,4-dioxane (DIOX), 1,3-dioxolane (DOL), methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, methyl difluoroacetate, methyl propionate, ethyl propionate, propyl propionate, methyl formate , Ethyl formate, ethyl butyrate, isopropyl butyrate, methyl isobutyrate, methyl cyanoacetate, vinyl acetate, diphenyl Disulfide, dimethyl sulfide, diethyl sulfide, adiponitrile, valeronitrile, glutaronitrile, malononitrile, succinonitrile, pimonitrile, suberonitrile, isobutyronitrile, biphenyl, thiophene, methyl ethyl ketone, fluorobenzene, hexafluorobenzene, carbonate electrolyte, glyme , Ether, acetonitrile, propiononitrile, γ-butyrolactone, γ-valerolactone, dimethyl sulfoxide (DMSO) ionic liquid, phosphazene, methyl formate, methyl acetate, ethyl propionate and other aliphatic carboxylic acid esters, or these compounds In which a part of the hydrogen atoms are substituted with fluorine atoms.

Examples of the supporting salt include 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 ) Lithium salts that can be used for ordinary lithium ion batteries such as ₂ can be used. The supporting salt can be used alone or in combination of two or more.

  A non-aqueous solvent can be used individually by 1 type or in combination of 2 or more types.

[Film outer package]
As the film of the exterior body, a laminate film having a surface layer, a metal layer, and an inner surface layer can be used. The metal layer may be aluminum, the surface layer may be nylon (registered trademark) or polyethylene terephthalate, and the inner surface layer may be a polyolefin resin such as polyethylene or polypropylene. The inner surface layer may be polyethylene having a melting point of 95 to 140 ° C or polypropylene having a melting point of 160 to 165 ° C.

  In this embodiment, as shown in FIGS. 1-3, the film exterior body 10 may be comprised by arrange | positioning two films 10-1 and 10-2 facing each other. Although not shown, a film outer package may be formed by folding a single film. The outline shape of the film outer package 10 is not particularly limited, but may be a quadrangle, and specifically, in this example, it is a rectangle. The films 10-1 and 10-2 are bonded to each other around the battery element 20 by thermal fusion, and the peripheral portion of the film outer package 10 is a thermal fusion portion 15. The heat fusion part 15 is formed over the entire periphery of the battery.

  In this example, the positive electrode tab 51 and the negative electrode tab 52 are drawn out from one side of the short side of the heat fusion part 15. Of course, the electrode tabs may be drawn from two or more different sides. In one embodiment, the positive electrode tab 51 and the negative electrode tab 52 are preferably parallel, but the present invention is not limited to this. Moreover, it is good also as a structure by which the cup part is not formed in the other film 10-2 while the cup part is formed in one film 10-1, like FIG. 2, FIG. Or it is good also as a structure (not shown) which forms a cup part in both films, and it is good also as a structure (not shown) which does not form a cup part in both.

[End structure of laminate]
4 and 5 are cross-sectional views schematically showing an end structure of a secondary battery according to one embodiment of the present invention. In addition, this cross section is a cross section cut by a cutting line extending in the width direction of the laminate (refer to the horizontal direction in FIG. 2).

(Positive electrode)
As shown in FIG. 4, a positive electrode active material layer 32 is formed on the upper surface of the metal foil 31 with respect to the structure on the upper surface side of the positive electrode metal foil 31 of the positive electrode 30. The structure on the lower surface side will be described later. In the present embodiment, the positive electrode active material layer 32 is not formed on the entire surface of the positive electrode metal foil 31, and is formed only in a region excluding the vicinity of both end portions of the metal foil 31. In other words, the positive electrode metal foil 31 has a region 31a where the positive electrode active material layer 32 is formed and a region 31b near both ends where the active material layer is not formed.

  The width of the region 31b of the active material non-formation portion is not particularly limited, but may be the same on the left and right, or may be different. As an example, the width of the region 31b is preferably 1 mm or more and 10 mm or less, and more preferably 2 mm or more and 6 mm or less.

  In the present embodiment, the structure on the lower surface side of the positive electrode metal foil 31 has the same configuration as the upper surface side. However, in the present invention, the structure on the upper surface side and the structure on the lower surface side of the metal foil do not need to be symmetric as described above, and may be asymmetric.

  The thickness of the positive electrode active material layer 32 is preferably 5 μm or more and 100 μm or less, and more preferably 30 μm or more and 80 μm or less.

(Insulating layer)
The insulating layer 70 is formed so as to cover the region 31a where the positive electrode active material layer 32 is formed and the region 31b where the active material layer 32 is not formed. Although FIG. 4 shows an example in which the insulating layer 70 has a substantially uniform thickness throughout, the present invention is not limited to this. As shown in FIG. 7, the surface of the insulating layer 70 may be formed to have substantially the same height, and the thickness may be different depending on the part.

  The insulating layer 70 is formed in one form so as to cover the entire surface of the positive electrode active material layer 32. However, the present invention is not necessarily limited to this. For example, when the separator 25 is disposed, the electrodes are insulated from each other by the separator 25. Therefore, it is not necessary to form the insulating layer 70 over the entire surface. The insulating layer 70 may be formed only on a part of the positive electrode active material layer 32. Specifically, for example, a substantially square-shaped insulating layer along the outer periphery of the positive electrode active material layer 32 may be used. In this case, the opening region where the insulating layer is not formed may be insulated by the separator 25.

  In the assembled state of the laminate, the structure is as shown in FIG. 5A. First, in the present embodiment, the area of the negative electrode active material layer 42 is larger than the area of the positive electrode active material 32, and as a result, the width of the negative electrode active material layer 42 is larger than the width of the positive electrode active material layer 32. It is getting longer. In the cross-sectional view of FIG. 5A, the end of the negative electrode active material layer 42 (also the negative electrode end) is located outside the end of the positive electrode active material layer 32 (in the direction away from the center of the battery in a plan view of the battery). ing. In other words, the end portion of the negative electrode active material layer 42 is provided so as to extend on the end portion of the positive electrode active material layer 32.

  Speaking of the relationship between the negative electrode end portion and the end portion of the positive electrode metal foil 31, the end portion of the positive electrode metal foil 31 is provided outside the negative electrode end portion. In other words, the end portion of the positive electrode metal foil 31 is provided so as to extend on the end portion of the negative electrode metal foil 41.

  With the above configuration, the following operational effects are achieved. That is, in the conventional battery structure as shown in FIG. 6, the area of the positive electrode 30 is smaller than that of the negative electrode 40, and the position of the end of the positive electrode metal foil 31 and the end of the positive electrode active material layer 32 are provided. The position is aligned. Therefore, if a burr 31p protrudes from the positive electrode metal foil 31, there is a possibility that the burr 31p contacts the adjacent negative electrode 40 and short-circuits. In FIG. 6, the separator 25 is disposed between the electrodes. Even if the separator 25 is present, the burr 31p may penetrate the separator 25 and cause a short circuit when the thickness is small.

  On the other hand, in the configuration of the present invention, since the positive electrode metal foil 31 extends to the outside of the negative electrode 40 (see FIG. 5A), the burr as shown in FIG. 6 protrudes toward the negative electrode side. Does not touch the negative electrode. On the other hand, the possibility of short-circuiting when burrs protrude from the negative electrode metal foil 41 toward the positive electrode is a problem. However, in the configuration of this embodiment, since the insulating layer 70 is formed on the positive electrode metal foil 31 in the region 31b where the active material layer is not formed, the burr from the negative electrode does not contact the positive electrode metal foil 31. Absent. Therefore, occurrence of a short circuit is prevented.

  The extension amount La of the positive electrode end portion from the negative electrode end portion should be 0.5 (mm) ≦ La ≦ 5.0 (mm) so that the above-described operational effects can be obtained satisfactorily. preferable. If it is less than 0.5 (mm), it is difficult to obtain the effect of such a configuration, and conversely, if it exceeds 5.0 (mm), the battery will be enlarged.

  In addition, as long as the said effect is show | played, the structure of an electrode can be variously changed. For example, as shown in FIG. 5B, the insulating layer 70 is not formed on the entire surface of the region 31 b of the positive electrode metal foil 31, but at least in a region where burrs from the negative electrode can be prevented from coming into contact with the metal foil 31. You may make it provide. Specifically, the end portion of the insulating layer 70 is 0.5 mm or more, preferably 1 mm or more outside the end portion of the negative electrode 40 (also the end portion of the negative electrode metal foil 41), and the positive electrode metal foil 31. The insulating layer 70 may be formed so as to be on the inner side than the end portion of. The insulating layer 70 only needs to be provided so as to extend on the end portion of the negative electrode 40, thereby preventing occurrence of a short circuit due to burrs.

  Regarding the distance Lb from the end of the positive electrode active material layer 32 to the end of the negative electrode, it is preferable that 0.5 (mm) ≦ Lb ≦ 5.0 (mm).

(Materials and production methods)
An insulating layer is an example and can form it by apply | coating the slurry composition for insulating layers so that a positive electrode active material layer may be coat | covered, and drying and removing a solvent. The insulating layer may be formed only on one side of the positive electrode. However, when the insulating layer is formed on both sides (particularly as a symmetrical structure), there is an advantage that the warping of the electrode can be reduced.

  The slurry composition for insulating layers is a slurry composition for forming a secondary battery porous film. The insulating layer slurry is composed of non-conductive particles and a binder having a specific composition, and the non-conductive particles, the binder and optional components are uniformly dispersed in a solvent as a solid content.

It is desired that the non-conductive particles exist stably in an environment where the lithium ion secondary battery is used and are electrochemically stable. As the non-conductive particles, for example, various inorganic particles, organic particles, and other particles can be used. Among these, inorganic oxide particles or organic particles are preferable, and in particular, it is more preferable to use inorganic oxide particles because of high thermal stability of the particles. The metal ions in the particles may form a salt in the vicinity of the electrode, which may cause an increase in the internal resistance of the electrode and a decrease in the cycle characteristics of the secondary battery. In addition, as other particles, the surface of conductive metal such as carbon black, graphite, SnO ₂ , ITO, metal powder and fine powder of conductive compound or oxide is surface-treated with a non-electrically conductive substance. By doing so, particles having electrical insulation properties can be mentioned. Two or more of the above particles may be used in combination as non-conductive particles.

As inorganic particles, inorganic oxide particles such as aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, BaTiO ₂ , ZrO, alumina-silica composite oxide; inorganic nitride particles such as aluminum nitride and boron nitride; silicone, diamond Covalent crystal particles such as barium sulfate, calcium fluoride, barium fluoride and the like, and sparingly soluble ion crystal particles such as talc and montmorillonite. These particles may be subjected to element substitution, surface treatment, solid solution, or the like, if necessary, or may be a single or a combination of two or more. Among these, inorganic oxide particles are preferable from the viewpoints of stability in an electrolytic solution and potential stability.

  The shape of the inorganic particles is not particularly limited, and may be a needle shape, a rod shape, a spindle shape, a plate shape, or the like. In particular, the shape of the inorganic particles may be a plate shape from the viewpoint of effectively preventing the needle-like material from penetrating. preferable.

  When the inorganic particles are plate-like, it is preferable to orient the inorganic particles in the porous film so that the flat plate surface is substantially parallel to the surface of the porous film. Thus, occurrence of a short circuit of the battery can be suppressed more favorably. This is because the inorganic particles are oriented as described above so that the inorganic particles are arranged so as to overlap each other on a part of the flat plate surface. Therefore, the voids (through holes) from one side of the porous film to the other side are linear. It is thought that it is formed in a bent shape (that is, the curvature is increased) instead of being able to prevent lithium dendrite from penetrating the porous film, and the occurrence of a short circuit is suppressed better. It is guessed.

Examples of the plate-like inorganic particles preferably used include various commercially available products, for example, “Sun Lovely” (SiO ₂ ) manufactured by Asahi Glass S-Tech, and pulverized products (TiO ₂ ) of “NST-B1” manufactured by Ishihara Sangyo Co., Ltd. , Sakai Chemical Industry's plate barium sulfate “H Series”, “HL Series”, Hayashi Kasei's “Micron White” (talc), Hayashi Kasei's “Bengel” (bentonite), Kawai Lime's “BMM” ”Or“ BMT ”(Boehmite),“ Cerasure BMT-B ”[Alumina (Al ₂ O ₃ )] manufactured by Kawai Lime Co.,“ Seraph ”(alumina) manufactured by Kinsei Matec Co., Ltd.,“ Yodogawa Mica Z- ”manufactured by Yodogawa Mining Co., Ltd. 20 "(sericite) etc. are available. In addition, SiO ₂ , Al ₂ O ₃ , and ZrO can be produced by the method disclosed in Japanese Patent Application Laid-Open No. 2003-206475.

  The average particle diameter of the inorganic particles is preferably in the range of 0.005 to 10 μm, more preferably 0.1 to 5 μm, and particularly preferably 0.3 to 2 μm. When the average particle diameter of the inorganic particles is within the above range, the dispersion state of the porous film slurry can be easily controlled, and thus the production of a porous film having a uniform predetermined thickness is facilitated. Furthermore, the adhesiveness with the binder is improved, and even when the porous film is wound, the inorganic particles are prevented from peeling off, and sufficient safety can be achieved even if the porous film is thinned. Moreover, since it can suppress that the particle filling rate in a porous film becomes high, it can suppress that the ionic conductivity in a porous film falls. Furthermore, the porous film can be formed thin.

  The average particle diameter of the inorganic particles is determined as an average value of the equivalent circle diameter of each particle by arbitrarily selecting 50 primary particles in an arbitrary field of view from an SEM (scanning electron microscope) image and performing image analysis. be able to.

  The particle size distribution (CV value) of the inorganic particles is preferably 0.5 to 40%, more preferably 0.5 to 30%, and particularly preferably 0.5 to 20%. By setting the particle size distribution of the inorganic particles within the above range, it is possible to maintain a predetermined gap between the non-conductive particles, so that the movement of lithium is inhibited and the resistance is increased in the secondary battery of the present invention. Can be suppressed. The particle size distribution (CV value) of the inorganic particles is obtained by observing the inorganic particles with an electron microscope, measuring the particle size of 200 or more particles, and obtaining the average particle size and the standard deviation of the particle size. Standard deviation) / (average particle diameter). It means that the larger the CV value, the larger the variation in particle diameter.

  When the porous insulating layer forming coating material is a non-aqueous solvent, a polymer that is dispersed or dissolved in the non-aqueous solvent can be used. Polymers dispersed or dissolved in non-aqueous solvents include polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), polyhexafluoropropylene (PHFP), polytrifluoroethylene chloride (PCTFE), polyperfluoroalkoxyfluoroethylene Can be used as a binder, but is not limited thereto.

  Since the insulating layer in one embodiment of the present invention is adjacent to the positive electrode, a high potential and stable one is preferable. In this sense, inorganic particles are more stable and preferable than organic particles. In addition, the binder that binds the insulating particles of the insulating layer is preferably excellent in voltage resistance, and preferably has a small HOMO value obtained by molecular orbital calculation. Polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), polyhexafluoropropylene (PHFP), polytrifluoroethylene chloride (PCTFE), polyperfluoroalkoxyfluoroethylene, etc. can be used as the binder. Although it is mentioned, it is not limited to these.

  In addition, a binder used for binding the mixture layer can be used.

  As the binder, when the porous insulating layer forming coating described later is an aqueous solvent (a solution using water or a mixed solvent containing water as a main component as a binder dispersion medium), the binder is dispersed or dissolved in the aqueous solvent. Can be used. Examples of the polymer that is dispersed or dissolved in the aqueous solvent include acrylic resins. As the acrylic resin, a homopolymer obtained by polymerizing monomers such as acrylic acid, methacrylic acid, acrylamide, methacrylamide, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, methyl methacrylate, ethylhexyl acrylate and butyl acrylate. Is preferably used. The acrylic resin may be a copolymer obtained by polymerizing two or more of the above monomers. Further, a mixture of two or more of the above homopolymers and copolymers may be used. In addition to the acrylic resins described above, polyolefin resins such as styrene butadiene rubber (SBR) and polyethylene (PE), polytetrafluoroethylene (PTFE), and the like can be used. These polymers can be used alone or in combination of two or more. Among these, it is preferable to use an acrylic resin. The form of the binder is not particularly limited, and a particulate (powdered) form may be used as it is, or a solution prepared in the form of a solution or an emulsion may be used. Two or more kinds of binders may be used in different forms.

  The porous insulating layer can contain materials other than the above-described inorganic filler and binder as necessary. Examples of such materials include various polymer materials that can function as a thickener for a porous insulating layer-forming paint described later. In particular, when an aqueous solvent is used, it is preferable to contain a polymer that functions as the thickener. As the polymer that functions as the thickener, carboxymethyl cellulose (CMC) and methyl cellulose (MC) are preferably used.

  Although it does not specifically limit, the ratio of the inorganic filler (namely, the total amount of the inorganic filler of a separator side part and an electrode side surface part) which occupies for the whole porous insulating layer is about 70 mass% or more (for example, 70 mass%-99 mass). %) Is suitable, preferably 80% by mass or more (for example, 80% by mass to 99% by mass), and particularly preferably about 90% by mass to 99% by mass.

  In addition, the proportion of the binder in the porous insulating layer is appropriately about 30% by mass or less, preferably 20% by mass or less, and particularly preferably 10% by mass or less (for example, about 0.5% by mass to 5% by mass). ). Moreover, when it contains porous insulating layer forming components other than an inorganic filler and a binder, for example, a thickener, it is preferable that the content rate of this thickener shall be about 5 mass% or less, and about 2 mass% or less ( For example, it is preferably about 0.5% by mass to 1% by mass. When the ratio of the binder is too small, the strength (shape retention) of the porous insulating layer itself is lowered, and defects such as cracks and peeling off may occur. When the ratio of the binder is too large, the gap between the particles of the porous insulating layer is insufficient, and the ion permeability of the porous insulating layer may be lowered.

  The porosity (porosity) of the porous insulating layer (ratio of the pore volume to the apparent volume) is preferably 20% or more, more preferably 30% or more in order to maintain the conductivity of ions. is necessary. However, if the porosity is too high, the porous insulating layer may fall off or crack due to friction or impact, so 80% or less is preferable, and 70% or less is more preferable.

  The porosity can be calculated from the ratio of the material constituting the porous insulating layer, the true specific gravity, and the coating thickness.

(Formation of porous insulation layer)
Next, a method for forming the porous insulating layer will be described. As a material for forming the porous insulating layer, a paste-like material (including slurry-like or ink-like, the same applies hereinafter) in which an inorganic filler, a binder and a solvent are mixed and dispersed is used.

  Examples of the solvent used for the coating material for forming the porous insulating layer include water or a mixed solvent mainly composed of water. As a solvent other than water constituting such a mixed solvent, one or more organic solvents (lower alcohol, lower ketone, etc.) that can be uniformly mixed with water can be appropriately selected and used. Alternatively, it may be an organic solvent such as N-methylpyrrolidone (NMP), pyrrolidone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, toluene, dimethylformamide, dimethylacetamide, or a combination of two or more thereof. Although the content rate of the solvent in the coating material for forming a porous insulating layer is not particularly limited, it is preferably 40 to 90% by mass, particularly about 50% by mass, based on the entire coating material.

  The operation of mixing the inorganic filler and binder with a solvent is performed by using a suitable kneader such as a ball mill, homodisper, dispermill (registered trademark), Claremix (registered trademark), fillmix (registered trademark), or an ultrasonic disperser. Can be used.

  The operation of applying the porous insulating layer-forming coating material can be used without any particular limitation on conventional general application means. For example, using a suitable coating device (gravure coater, slit coater, die coater, comma coater, dip coat, etc.), a predetermined amount of coating material for forming a porous insulating layer is coated to a uniform thickness. obtain.

  Thereafter, the coating material is dried by a suitable drying means (typically a temperature lower than the melting point of the separator, for example, 110 ° C. or less, for example, 30 to 80 ° C.), thereby removing the solvent in the coating material for forming the porous insulating layer. It is good to remove.

(Thickness)
The thickness of the insulating layer is preferably 1 μm or more and 30 μm or less, and more preferably 3 μm or more and 15 μm or less. Further, regarding the thickness of each part of the insulating layer 70, it is preferable that ta ≦ tb, where ta is the thickness of the insulating layer on the positive electrode active material layer 32 and tb is the thickness on the positive metal foil 31.

  When the thickness of the insulating layer on the positive electrode active material layer 32 is ta and the thickness of the positive electrode active material layer 32 is tc, it is preferable that ta ≦ tc.

(Porosity)
The porosity of the insulating layer 70 is preferably 30% or more and 70% or less, and more preferably 35% or more and 60% or less.

  With respect to the porosity of each part of the insulating layer 70, when the porosity of the insulating layer on the positive electrode active material layer 32 is Pa and the porosity Pb of the insulating layer on the positive electrode metal foil 31 is Pa ≦ Pb or Pa < Pb is preferable. Thus, since the thickness per same weight increases by making the porosity of the insulating layer on the metal foil 31 high, the effect which prevents a burr | flash increases more. In addition, since the insulating layer can hold a larger amount of electrolyte and the electrolyte can be appropriately replenished to the active material layer, a longer life can be expected.

  It is preferable that Pc ≦ Pa, where Pc is the porosity of the positive electrode active material layer and Pa is the porosity of the insulating layer on the positive electrode active material layer 32.

(Production method of electrode)
The lithium ion secondary battery according to the present embodiment can be manufactured according to the following method. Here, an example of a method for manufacturing a lithium ion secondary battery will be described by taking a laminated laminate type lithium ion secondary battery as an example.

  The production of the positive electrode and the negative electrode will be briefly described. First, as shown in FIG. 9, an active material layer 211 in a rectangular region is applied on a long metal foil 201 as an example.

  Then, as an example, a rectangular region insulating layer 215 is applied so as to cover the active material layer 211. Note that the positive electrode active material coating step and the insulating layer coating step may be performed simultaneously.

  Thereafter, as a slitting process, the metal foil 211 is cut in the longitudinal direction along the lines L1 and L2 (FIG. 10). The lines L1 and L2 are set to pass through a region where the active material layer 211 is not present and only the insulating layer 215 is coated.

  Next, as shown in FIG. 11, the electrode 30 is obtained by punching the metal foil 201 </ b> A that has been cut off at both ends in the slit process. The electrode 30 has a substantially rectangular shape as a whole, and has a protruding portion 31t at a part of the outer peripheral portion thereof. The protruding portion 31t is a portion for electrical connection, and is basically a portion where no active material layer or insulating layer is formed. The negative electrode can be produced in the same manner as described above, but in the case of the negative electrode, it is not necessary to form an insulating layer.

  The end structure of the laminated body described above is preferably provided on both sides 15A and 15B of the battery as shown in FIG. The reason for this is that burrs are relatively easy to occur in the slit process described above, and when the end structures according to the present invention are provided on both sides as described above, it is possible to effectively prevent the occurrence of problems due to the burrs. This is because it can.

  Or you may make it provide the edge part structure which concerns on this invention also in other 15 C of side like FIG.8 (b).

3. Other configurations [Battery]
A plurality of lithium ion secondary batteries according to this embodiment can be combined to form an assembled battery. For example, the assembled battery may have a configuration in which two or more lithium ion secondary batteries according to the present embodiment are used and connected in series, in parallel, or both. Capacitance and voltage can be freely adjusted by connecting in series and / or in parallel. About the number of the lithium ion secondary batteries with which an assembled battery is provided, it can set suitably according to battery capacity or an output.

[vehicle]
The lithium ion secondary battery or its assembled battery according to this embodiment can be used in a vehicle. Vehicles according to this embodiment include hybrid vehicles, fuel cell vehicles, and electric vehicles (all include four-wheel vehicles (passenger cars, trucks, buses and other commercial vehicles, light vehicles, etc.), motorcycles (motorcycles), and tricycles. ). Note that the vehicle according to the present embodiment is not limited to an automobile, and may be used as various power sources for other vehicles, for example, moving bodies such as trains.

[Power storage device]
The lithium ion secondary battery or its assembled battery according to this embodiment can be used for a power storage device. As the power storage device according to the present embodiment, for example, a power source connected to a commercial power source supplied to a general household and a load such as a home appliance, and used as a backup power source or auxiliary power at the time of a power failure, Examples include photovoltaic power generation, which is also used for large-scale power storage for stabilizing power output with a large time fluctuation due to renewable energy.

[Others]
Furthermore, the lithium ion secondary battery or its assembled battery according to the present embodiment can be used as a power source for mobile devices such as mobile phones and notebook computers.

(Appendix)
This application discloses the following invention:
1. A: a first electrode (30) having a first metal foil and a first active material layer formed on the metal foil;
B: has a second metal foil and a second active material layer formed on the metal foil, and the area of the second active material layer is the area of the first active material layer when seen in a plan view A second electrode (40) having a polarity different from that of the first electrode,
C: an insulating layer (70) formed on the first electrode so as to be interposed between both electrodes;
With
The first electrode (30) includes a region (31a) where the first active material layer is formed on the first metal foil, and an electrical connection portion (31t) where the active material layer is not formed. ) Other than the region (31b),
When the cut surface of the laminate is viewed, the end of the first metal foil (31) extends outward from the end of the second metal foil (41), and
The insulating layer (70) is formed on the first active material layer (32), and an end portion of the second electrode (40) in the region (31b) where the active material is not formed. A secondary battery, wherein the secondary battery is formed to at least a position outside.

The secondary battery according to one embodiment of the present invention may also be defined as follows:
A: a first electrode (30) having a first metal foil and a first active material layer formed on the metal foil;
B ′: a second metal foil and a second active material layer formed on the metal foil, the end of the second active material layer being on the end of the first active material layer A second electrode (40) provided extending and having a different polarity from the first electrode;
C: an insulating layer (70) formed on the first electrode so as to be interposed between the two electrodes;
With
The first electrode (30) includes a region (31a) in which the first active material layer is formed on the first metal foil and an electrical connection portion (31t) in which no active material layer is formed. And a region (31b) other than
An end portion of the first metal foil (31) is provided to extend on an end portion of the second metal foil (41); and
The insulating layer (70) is formed on the first active material layer (32), and an end portion of the second electrode (40) in the region (31b) where the active material is not formed. A secondary battery, characterized by being provided extending above.

2. When the amount of extension of the end of the first metal foil (31) from the end of the second metal foil (41) is La,
0.5 (mm) ≤ La ≤ 5.0 (mm)
The secondary battery as described above, wherein the above formula is satisfied.

3. When the distance from the end of the first active material layer (32) to the end of the second metal foil (41) is Lb,
0.5 (mm) ≤ Lb ≤ 5.0 (mm)
The secondary battery as described above, wherein the above formula is satisfied.

4). The secondary battery as described above, wherein the insulating layer (70) has a thickness in the range of 1 µm to 30 µm.

5). The thickness of the insulating layer on the region (31a) including the first active material layer is ta,
When the thickness of the insulating layer on the region (31b) not including the first active material layer is tb,
ta ≦ tb
The secondary battery as described above, wherein the above formula is satisfied.

6). The secondary battery as described above, wherein a porosity of the insulator layer (70) is in a range of 30% to 70%.

7). D: The secondary battery as described above, further comprising a separator (25) disposed between the positive electrode and the negative electrode.

8). The secondary battery as described above, wherein the first electrode is a positive electrode and the second electrode is a negative electrode.

DESCRIPTION OF SYMBOLS 1 Film exterior battery 10 Film exterior body 15 Heat-fusion part 15A-15C Side 20 Battery element 25 Separator 30 Positive electrode 31 Positive electrode metal foil 31a, 31b Area | region 31p Burr 31t Protrusion part 32 Positive electrode active material layer 40 Negative electrode 41 Negative electrode metal foil 42 Negative electrode Active material layer 70 Insulating layer 201 Metal foil 211 Active material layer 215 Insulating layer

Claims (7)

A first electrode having a first metal foil and a first active material layer formed on the metal foil;
A second metal foil and a second active material layer formed on the metal foil, wherein an area of the second active material layer is larger than an area of the first active material layer in a plan view; A large second electrode having a different polarity from the first electrode;
An insulating layer formed on the first electrode so as to be interposed between the two electrodes;
With
The first electrode has a region where the first active material layer is formed on the first metal foil and a region other than the electrical connection portion where the active material layer is not formed. ,
When the cut surface of the laminate is viewed, the end of the first metal foil extends outward from the end of the second metal foil, and
The insulating layer is formed on the first active material layer, and in a region where no active material is formed, the insulating layer is formed at least outside the end of the second electrode. Characterized by
When the amount of extension of the end of the first metal foil from the end of the second metal foil is La,
0.5 (mm) ≤ La ≤ 5.0 (mm)
A secondary battery characterized by satisfying the above formula . When the distance from the end of the first active material layer to the end of the second metal foil is Lb,
0.5 (mm) ≤ Lb ≤ 5.0 (mm)
The secondary battery according to claim 1 , wherein the above formula is satisfied. The thickness of the insulating layer is in the range of 1μm or more 30μm or less, secondary battery according to claim 1 or 2. The thickness of the insulating layer on the region including the first active material layer is ta,
When the thickness of the insulating layer on the region not including the first active material layer is tb,
ta ≦ tb
And satisfies the above equation, the secondary battery according to any one of claims 1-3. A first electrode having a first metal foil and a first active material layer formed on the metal foil;
A second metal foil and a second active material layer formed on the metal foil, wherein an area of the second active material layer is larger than an area of the first active material layer in a plan view; A large second electrode having a different polarity from the first electrode;
An insulating layer formed on the first electrode so as to be interposed between the two electrodes;
With
The first electrode has a region where the first active material layer is formed on the first metal foil and a region other than the electrical connection portion where the active material layer is not formed. ,
When the cut surface of the laminate is viewed, the end of the first metal foil extends outward from the end of the second metal foil, and
The insulating layer is formed on the first active material layer, and in a region where no active material is formed, the insulating layer is formed at least outside the end of the second electrode. Features
The porosity of the insulation layer is in the range of 30% to 70%, the secondary battery. further,
The secondary battery as described in any one of Claims 1-5 provided with the separator arrange | positioned between the said 1st electrode and the said 2nd electrode . The secondary battery according to any one of claims 1 to 6 , wherein the first electrode is a positive electrode and the second electrode is a negative electrode.

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