JP7264289B2 - ELECTRODE, METHOD FOR MANUFACTURING ELECTRODE, AND STORAGE ELEMENT - Google Patents

Description

The present invention relates to an electrode, an electrode manufacturing method, and an electric storage element.

In a non-aqueous electrolyte secondary battery represented by a lithium-ion secondary battery, a method of coating a mixture layer containing an active material with an insulating layer is sometimes used as a method for improving the safety thereof. By providing the insulating layer, insulation between the positive and negative electrodes is ensured even when the separator shrinks or breaks. More specifically, for an electrode having a current collector foil and a mixture layer provided on the current collector foil, an insulating layer is provided between the edges of the mixture layer and the current collector foil in order to prevent short circuits at the ends of the electrode. In addition, in order to prevent short-circuiting of the mixture layer between the positive electrode and the negative electrode, a method of coating (overcoating) the surface of the mixture layer of at least one electrode with an insulating layer is known. there is

Republished patent WO2010/116533 JP 2016-225077 A

The insulating layer is usually composed of insulating particles. When forming such an insulating layer, increasing the size of the insulating particles to improve battery performance due to the permeability of the electrolyte into the insulating layer may cause metal contamination to enter the edge of the mixture layer. However, it is difficult to achieve both maintenance of battery performance and prevention of intrusion of metal contaminants.

An electrode of the present invention includes a current collector foil and a mixture layer formed on the current collector foil, and at least a portion of an end portion of the mixture layer is a first insulating material containing first insulating particles. at least part of the planar portion of the mixture layer is covered with a second insulating layer containing second insulating particles, and the average particle diameter of the first insulating particles is equal to that of the second insulating particles Smaller than the average particle size.

According to the present invention, the insulating particles having different average particle diameters are used to form the insulating layer at the end portion of the mixture layer and the planar portion of the mixture layer, thereby suppressing the deterioration of the battery performance and It is possible to provide an electrode that can prevent contamination from entering.

1 is a schematic cross-sectional view of an electrode according to one embodiment of the invention; FIG. 1 is a schematic partial cross-sectional view of an electrode according to one embodiment of the invention; FIG. 1 is a partially broken perspective view showing a schematic configuration of a non-aqueous electrolyte secondary battery according to one embodiment of the present invention; FIG.

A. Electrode Overview FIG. 1 is a schematic cross-sectional view of an electrode according to one embodiment of the present invention. The electrode 101 includes a collector foil 10 and a mixture layer 20 formed on the collector foil. At least part of the end portion 21 of the mixture layer 20 is covered with the first insulating layer 30, and at least part of the planar portion 22 of the mixture layer 20 is covered with the second insulating layer 40. there is

The first insulating layer 30 includes first insulating particles 31 . Second insulating layer 40 also includes second insulating particles 41 . The average particle size of the first insulating particles 31 is smaller than the average particle size of the second insulating particles 41 .

In this specification, the plane portion 22 of the mixture layer 20 means a surface of the electrode 101 opposite to the current collector foil 10 of the mixture layer 20 and having a substantially constant thickness. . Further, the end portions 21 of the mixture layer 20 refer to inclined portions of the mixture layer 20, and refer to portions where the thickness of the mixture layer is gradually smaller at both ends of the plane portion than at the plane portion. . FIG. 2(a) is a schematic partial cross-sectional view showing an end portion of the mixture layer of the electrode shown in FIG. In this embodiment, the first insulating particles 31 adhere to the entire end portion 21 (inclined portion) of the mixture layer 20 to form the first insulating layer. FIG. 2(b) is a schematic partial cross-sectional view showing an end portion of a mixture layer of an electrode according to another embodiment of the present invention. In this embodiment, the first insulating particles 31 adhere to a portion of the end portion 21 (inclined portion) of the mixture layer 20 to form the first insulating layer. FIG. 2(c) is a schematic partial cross-sectional view showing an end portion of a mixture layer of an electrode according to still another embodiment of the present invention. In this embodiment, the first insulating particles 31 adhere to the edge portion 21 (inclined portion) of the mixture layer 20 and the vicinity of the flat portion 22 of the mixture layer 20 to form the first insulating layer. ing. As described above, the second insulating layer adheres to at least a portion of the flat portion 22. As shown in FIG. It may also adhere to the part. Moreover, as illustrated in FIG. 2B, the first insulating layer and the second insulating layer may overlap each other. By overlapping the first insulating layer and the second insulating layer, the entire surface of the mixture can be reliably covered with the insulating layer. In one embodiment, the first insulating layer and the second insulating layer overlap at the edge of the mixture layer. The electrode can be prevented from becoming thicker by overlapping the end portion of the mixture layer, which is thinner than the flat portion of the mixture layer. Preferably, the second insulating layer is arranged on the first insulating layer in the overlapping portion. The above-mentioned "peripheral vicinity of the flat portion" means an area within 5 mm (preferably within 2 mm) from the boundary between the flat portion and the inclined portion.

By constructing a non-aqueous electrolyte secondary battery using the electrode of the present invention having an insulating layer, insulation between the positive and negative electrodes can be ensured even when the separator shrinks or the membrane breaks. In the present invention, by using the first insulating particles having a relatively small particle size, it is possible to narrow the gaps between the insulating particles and form the first insulating layer. As a result, the first insulating layer effectively prevents contamination (particularly metal contamination) from entering the material mixture layer. On the other hand, by using the second insulating particles having a relatively large particle size, it is possible to widen the gaps between the insulating particles and form the second insulating layer. As a result, the second insulating layer has excellent electrolyte permeability. In the present invention, in order to form a first insulating layer in which first insulating particles are densely present at the end of the mixture layer where contamination is likely to enter, and to arrange the first insulating layer so as to face the counter electrode To obtain an electrode capable of preventing the intrusion of metal contamination while suppressing the deterioration of battery performance by forming a second insulating layer with excellent electrolyte permeability on the surface of a mixture layer into which contamination hardly penetrates. can be done.

In one embodiment, as shown in FIG. 1, the electrode 101 includes a mixture layer forming region 11 in which the mixture layer 20 is formed and a mixture layer non-forming region 12 in which the mixture layer is not formed. (that is, the current collector foil 10 is composed of the mixture layer forming region 11 and the mixture layer non-forming region 12). In one embodiment, in the vicinity of the boundary between the mixture layer forming region 11 and the mixture layer non-forming region 12, at least part of the current collector foil 10 (mixture layer non-forming region) is the first insulating layer. covered by 30. In other words, in this embodiment, the first insulating layer 30 continuously covers at least part of the end portion 21 of the mixture layer 20 and at least part of the current collector foil 10 . By configuring the first insulating layer 30 in such a manner, the insulating effect and the effect of preventing contamination from entering become remarkable.

When the first insulating layer is formed near the boundary between the mixture layer forming region and the mixture layer non-forming region, the first insulating layer is formed on the current collector foil (mixture layer non-forming region). The range is preferably 2 mm to 10 mm from the vicinity of the boundary between the mixture layer forming area and the mixture layer non-forming area.

INDUSTRIAL APPLICABILITY The electrode of the present invention is used as a positive electrode or a negative electrode of a non-aqueous electrolyte secondary battery typified by a lithium ion secondary battery. In one embodiment, the electrode of the present invention is used as a positive electrode for non-aqueous electrolyte secondary batteries. By using a positive electrode on which an insulating layer is formed, contact between the separator and the positive electrode mixture layer can be avoided, and oxidation of the separator can be prevented.

B. First Insulating Layer As described above, the first insulating layer is composed of first insulating particles.

The average particle size of the first insulating particles is preferably less than 1.8 μm, more preferably 0.2 μm to 1.2 μm, still more preferably 0.2 μm to 0.8 μm. With such a range, the gaps between the particles can be made small, so that the first insulating layer can be formed into which contaminants are more difficult to enter.

As used herein, the "average particle size" is based on the particle size distribution measured by a laser diffraction/scattering method for a diluted solution in which particles are diluted with a solvent in accordance with JIS-Z-8815 (2013). It means a value at which the volume-based cumulative distribution calculated according to JIS-Z-8819-2 (2001) is 50%.

D10, D50 and D90 of the first insulating particles preferably satisfy the relationship of (D90-D10)/D50≧0.7, and more preferably satisfy the relationship of (D90-D10)/D50≧0.85. Fulfill. In addition, D10 means a value at which the volume-based integrated portion is 10% in the particle size distribution, and D50 means a value at which the volume-based integrated distribution is 50% (i.e., the average particle diameter), D90 means a value at which the volume-based integrated distribution is 90%. The D10, D50 and D90 relationships above indicate a broad particle size distribution. If such a relationship is satisfied, small particles can easily enter between particles of large particles, and the first insulating layer can be formed to which contaminants are less likely to enter. It should be noted that (D90-D10)/D50 of the first insulating particles is preferably as large as possible, but its upper limit is, for example, 1.5.

Any appropriate material can be used as the material forming the first insulating particles as long as it has insulating properties. Materials constituting the first insulating particles include, for example, metal oxides such as alumina, boehmite, aluminum hydroxide, silica, zirconia, and magnesia. Silicides such as silicon carbide, nitrides such as aluminum nitride, and the like may also be used. The shape of the first insulating particles is not particularly limited, but from the viewpoint of coatability and electrolyte permeability, a spherical shape or a block shape is preferable. Here, the term "spherical" or "aggregate" refers to a shape having an aspect ratio of 1.5 or less.

In one embodiment, the first insulating layer further includes a first binder. The first binder has a function of binding the first insulating particles together, and by using the first binder, it is possible to form the first insulating layer from which the first insulating particles are less likely to detach. .

Any appropriate material can be used as the first binder as long as the effects of the present invention can be obtained. Examples of the first binder include fluororesins such as polyvinylidene fluoride, polytetrafluoroethylene, and fluororubber, thermoplastic resins such as polypropylene, polyethylene and polyvinyl acetate resins, and polyacrylic acids such as polymethyl methacrylate. Examples thereof include resins, imide resins such as polyimide and polyamideimide, alkoxysilyl group-containing resins, and rubbers such as styrene-butadiene rubber (SBR).

The content of the first binder is preferably 1 part by weight to 30 parts by weight, more preferably 1 part by weight to 15 parts by weight, and even more preferably, with respect to 100 parts by weight of the first insulating layer. is 3 to 10 parts by weight. Within such a range, the first insulating layer can be formed from which the first insulating particles are less likely to be detached. When the first insulating layer is formed by the dry coating method described later, the content of the first binder is 10 parts by weight to 30 parts by weight with respect to 100 parts by weight of the first insulating layer. is preferred.

The area of the first insulating layer is preferably 20% or more, more preferably 30% or more, of the total area of the ends (inclined portions) of the mixture layer.

C. Second Insulating Layer As described above, the second insulating layer is composed of second insulating particles. Preferably, the second insulating layer further includes a second binder. The second binder has a function of binding the second insulating particles together, and by using the second binder, it is possible to form a second insulating layer from which the second insulating particles are difficult to detach. .

The average particle diameter of the second insulating particles is preferably 1.8 μm or more, more preferably 1.8 μm to 5.0 μm, particularly preferably 1.8 μm to 3.5 μm. With such a range, the gaps between the insulating particles can be increased, so that the second insulating layer can be formed with excellent electrolyte permeability. In addition, it is possible to prevent the second insulating particles from easily entering between the active material particles of the mixture layer.

The ratio of the average particle size of the second insulating particles to the average particle size of the first insulating particles (average particle size of the second insulating particles/average particle size of the first insulating particles) is preferably 1.5. 2 to 8, more preferably 1.5 to 6. Within such a range, it is possible to obtain an electrode that satisfactorily achieves both improved penetration of the electrolytic solution into the material mixture layer and prevention of metal contaminants from entering the material mixture layer.

D10, D50 and D90 of the second insulating particles preferably satisfy the relationship of (D90-D10)/D50≦0.8, and more preferably satisfy the relationship of (D90-D10)/D50≦0.7. Fulfill. The above relationships among D10, D50 and D90 indicate that the particle size distribution is narrow and the particle sizes are uniform. Since the particles have approximately the same particle size, gaps are likely to occur between the particles, and if D10, D50, and D90 satisfy the above relationship, a second insulating layer having remarkably excellent electrolyte permeability is formed. be able to. It should be noted that (D90-D10)/D50 of the second insulating particles is preferably as small as possible, but its lower limit is, for example, 0.5.

Any appropriate material can be used as the material forming the second insulating particles as long as it has insulating properties. As a material for forming the second insulating particles, for example, the material described in the section B above can be used.

Any appropriate material can be used as the material constituting the second binder as long as the effects of the present invention can be obtained. As the material constituting the second binder, for example, the material described in the above section B can be used.

The content of the second binder is preferably 1 part by weight to 30 parts by weight, more preferably 1 part by weight to 15 parts by weight, with respect to 100 parts by weight of the second insulating layer. It is preferably 3 to 15 parts by weight. With such a range, it is possible to form a second insulating layer from which the second insulating particles are less likely to be detached. When the second insulating layer is formed by a dry coating method, which will be described later, the content of the second binder is 10 parts per 100 parts by weight of the second insulating layer.
Parts by weight to 30 parts by weight are preferred.

The thickness of the second insulating layer is preferably 2 μm to 15 μm, more preferably 3 μm to 10 μm.

The ratio of the thickness of the second insulating layer to the average particle size of the second insulating particles (thickness/average particle size) is preferably 1 to 8, more preferably 1.2 to 5, and even more preferably 1.2 to 3. Within such a range, it is possible to form a second insulating layer having excellent insulating properties with little adverse effect on battery performance. Further, by using a dry coating method, which will be described later, it is possible to reduce the ratio of the thickness of the second insulating particles to the average particle diameter while preventing the resistance of the mixture layer from increasing. Since the mass of the material mixture layer can be increased by reducing the thickness of the second insulating layer, the energy density of the battery can be increased.

The area of the second insulating layer is preferably 90% or more, more preferably 95% or more, and particularly preferably 100% of the total area of the plane portions of the mixture layer.

The porosity of the second insulating layer is preferably 10% to 50%, more preferably 15% to 35%. It is possible to form a second insulating layer that has little adverse effect on battery performance and is excellent in insulating properties.

D. Current Collector Foil As the current collector foil, any suitable current collector foil commonly used in non-aqueous electrolyte secondary batteries can be used. When the electrode is configured as a negative electrode, for example, a metal foil such as copper foil is used as the current collector foil. When the electrode is configured as a positive electrode, for example, a metal foil such as an aluminum foil is used as the collector foil.

E. Mixture Layer In one embodiment, when the electrode is configured as a negative electrode, the mixture layer contains a negative electrode active material capable of intercalating and deintercalating lithium ions. Examples of negative electrode active materials include graphite (flaky graphite, flaky graphite, earthy graphite, artificial graphite), cokes, carbon materials such as activated carbon, aluminum, alloys of silicon and lithium, metallic lithium, LiFe2O3, WO2, and MoO2. , SiO, and CuO. The negative electrode active material may be used alone or in combination of two or more.

In another embodiment, when the electrode is configured as a positive electrode, the mixture layer contains a positive electrode active material capable of intercalating and deintercalating lithium ions. As the positive electrode active material, a composite oxide represented by a composition formula LixMO2, LiyM2O4, NaxMO2 (where M is one or more transition metals, 0≤x≤1, 0≤y≤2), a tunnel structure, or a layered structure. transition metal oxides that occlude and release lithium, such as metal chalcogenides and metal oxides, can be used. Specific examples include LiCoO2, LiNiO2, LiNi1/2Mn1/2O2, LiNi1/3Mn1/3Co1/3O2, LiCoxNi1-xO2, LiMn2O4 and Li2Mn2O4.

The mixture layer may further contain additives such as binders, conductive agents, thickeners and fillers. Examples of binders include polyvinylidene fluoride, styrene-butadiene rubber, carboxymethylcellulose, polytetrafluoroethylene, polyethylene, polypropylene, polyacrylonitrile, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, fluororubber, Examples include vinylidene fluoride-hexafluoropropylene copolymer. Examples of conductive agents include carbon materials such as acetylene black and carbon black.

F. Method for Manufacturing Electrode The above-described electrode is produced by applying first insulating particles and second insulating particles together with a binder to a laminate composed of a collector foil and a mixture layer, and forming a first insulating layer and a second insulating particle. It can be manufactured by forming a second insulating layer. The first insulating particles are applied to the end portion (inclined portion) of the mixture layer. In one embodiment, the first insulating particles are applied in the vicinity of the boundary between the mixture layer forming region and the mixture layer non-forming region. A first insulating layer is formed on at least a portion of the electrical foil (a region where the mixture layer is not formed). Moreover, the first insulating particles may be applied so that the first insulating particles adhere to the vicinity of the periphery of the planar portion of the mixture layer. The second insulating particles are applied to the planar portion of the mixture layer facing the counter electrode. The second insulating layer is preferably coated on the entire planar portion of the mixture layer. By doing so, it is possible to prevent a short circuit between the positive electrode and the negative electrode when the separator shrinks or breaks. Also, the second insulating particles may be applied so as to adhere to a part of the edge of the mixture layer.

It is preferable to apply the second insulating particles to the planar portion of the mixture layer after the first insulating particles are applied to the ends of the mixture layer. By forming the first insulating layer and the second insulating layer in this manner, the first insulating particles and the mixture layer are brought into contact with each other. As a result, the first insulating particles and the binder are likely to enter the irregularities on the surface of the material mixture layer, blocking some of the active material particles, thereby further preventing the entry of contaminants.

Any appropriate method can be adopted as a method of forming the first insulating layer and the second insulating layer. For example, a wet coating method in which a slurry-like insulating layer forming material containing insulating particles, a binder and a solvent (e.g., NMP) is applied, or a dry coating method in which insulating particles and binder particles are combined without using a solvent and coated. An insulating layer can be formed by applying insulating particles and a binder to a laminate composed of a collector foil and a mixture layer by a coating method or the like. Here, dry coating is a method of coating without using a solvent.

In one embodiment, the first insulating layer is formed by a wet coating method and the second insulating layer is formed by a dry coating method. By forming the first insulating layer by a wet coating method, the binder penetrates into the edge of the material mixture layer together with the solvent, and the gaps between the active material particles can be closed with the binder. Therefore, it is possible to further prevent contamination from entering. On the other hand, by forming the second insulating layer by a dry coating method, it is possible to prevent the binder from penetrating between the active material particles in the planar portion of the material mixture layer. Therefore, it is possible to prevent the resistance from increasing without lowering the permeability of the electrolytic solution into the mixture layer. Furthermore, by using the dry coating method, insulating particles having a large particle size can be coated uniformly and thinly. It is suitable for forming an insulating layer.

It is preferable that the first insulating layer and the second insulating layer overlap at the ends of the mixture layer. Since the first insulating layer and the second insulating layer overlap each other, the insulating layer can reliably cover the entire mixture surface. In addition, by overlapping the end portion of the mixture layer, which is thinner than the flat portion of the mixture layer, it is possible to prevent the electrode from becoming thicker.

One embodiment of the dry coating method is electrostatic coating, in which a composite of insulating particles and binder particles is adhered to a laminate composed of a collector foil and a mixture layer by electrostatic attraction. More specifically, (i) a step of mixing insulating particles and a particulate binder (hereinafter also referred to as binder particles) to obtain a composite, (ii) electrostatic coating to obtain the composite, An insulating layer is formed through a step of adhering to a laminate composed of a collector foil and a mixture layer, and (iii) a step of heating the composite. When the second insulating layer is formed by dry coating, in the step (ii), the composite (composite composed of the second insulating particles and the second binder particles) is a mixture layer is attached to the flat portion of the (and part of the edge if desired).

The average particle size of the second binder particles (average particle size before heating) is preferably 0.1 μm to 0.5 μm, more preferably 0.15 μm to 0.3 μm. Within such a range, the second insulating layer having excellent insulating properties and electrolyte permeability can be formed. The average particle size of the binder particles (average particle size before heating) is preferably smaller than the average particle size of the second insulating particles.

In the electrostatic coating, a laminate composed of the collector foil and the mixture layer and a composite of insulating particles and binder particles are put into a coating booth equipped with electrodes for electrostatic coating. The laminate and the composite are charged, and the composite is adhered to the laminate composed of the collector foil and the mixture layer by electrostatic attraction. At this time, it is preferable to use a mask or the like to prevent the composite from adhering to portions where the formation of the insulating layer is not desired. For example, the second insulating layer can be prevented from being formed on the current collector foil (mixture layer non-formation region) by masking the current collector foil (mixture layer non-formation region).

After the electrostatic coating, the laminate to which the composite has adhered is heated to fuse the binder particles and fix the insulating particles and the binder particles. The heating temperature can be any appropriate temperature depending on the type of binder particles. Examples of the heating method include a method in which the laminate with the composite adhered thereto is put into a heating furnace, and a method in which the laminate with the composite adhered is heated while being pressed using a heating roll.

An example of an embodiment of a method for manufacturing an electrode is shown below.
1. A slurry-like positive electrode mixture layer-forming material is prepared by mixing a positive electrode active material, a binder for a positive electrode mixture layer, a conductive agent, and a solvent in a predetermined ratio. The positive electrode mixture layer-forming material is applied on a strip-shaped collector foil in the longitudinal direction of the strip. In this coating, the positive electrode mixture layer-forming material is applied onto the current collector foil in a width narrower than the width of the current collector foil. The positive electrode mixture layer is formed by heating the positive electrode mixture layer forming material to volatilize the solvent.
2. By mixing the first insulating particles, the first binder and the solvent in a predetermined ratio, a slurry-like first insulating layer forming material is produced. The slurry-like first insulating layer-forming material is applied along the longitudinal direction of the current collector foil near the boundary between the mixture layer forming region and the mixture layer non-forming region of the positive electrode mixture layer. That is, the first insulating layer-forming material is applied to part of the current collector foil and part of the end of the positive electrode mixture layer. After coating, the first insulating layer is formed by heating to volatilize the solvent. By applying the first insulating layer-forming material before heating the positive electrode mixture layer-forming material and heating after the coating, the solvent of the positive electrode mixture layer-forming material and the first insulating layer-forming material are mixed. and the solvent may be volatilized at the same time.
3. By mixing the second insulating particles and the particles of the second binder by mechanofusion or the like, a composite is formed in which the second binder particles are adhered to the surfaces of the second insulating particles. The composite is adhered to the planar portion of the positive electrode mixture layer by the above electrostatic coating. A second insulating layer is formed by heating after the deposition.

G. Nonaqueous Electrolyte Secondary Battery FIG. 3 is a partially broken perspective view showing a schematic configuration of a nonaqueous electrolyte secondary battery according to one embodiment of the present invention. A non-aqueous electrolyte secondary battery 110 includes a positive electrode 100 having a current collector foil and a positive electrode mixture layer, and a negative electrode 200 having a current collector foil and a negative electrode mixture layer. Typically, as shown in FIG. 3, a non-aqueous electrolyte secondary battery 110 includes a power generation element 111 configured by winding a positive electrode 100 and a negative electrode 200 with a separator 300 sandwiched therebetween. The power generation element 111 is housed in the battery case 112 with the separator 300 impregnated with the non-aqueous electrolyte. The battery case 112 is, for example, substantially box-shaped with an opening on the upper surface side. The opening is closed by a plate-shaped battery lid 113 . A positive electrode terminal 114 and a negative electrode terminal 115 are provided on the battery cover 113 , and the positive electrode terminal 114 is connected to the positive electrode 100 and the negative electrode terminal 11 via a positive lead 116 .
5 are electrically connected to the negative electrode 200 through the negative electrode lead 117 .

Any appropriate non-aqueous electrolyte can be used as the non-aqueous electrolyte. A non-aqueous electrolyte includes a non-aqueous solvent and an electrolyte salt. Examples of non-aqueous solvents include linear carbonates such as ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and diphenyl carbonate; ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, styrene carbonate, etc. These non-aqueous solvents may be used singly or in combination of two or more. Examples of electrolyte salts include ionic compounds such as LiPF6, LiPF2(C2O4)2, LiPF3(CF2CF3)3, LiPF4(C2O4), LiClO4, LiBF4, LiAsF6.

As the separator, for example, a microporous film or the like containing polyolefin resin such as polyethylene or polypropylene as a main component is used. The microporous membrane may be used alone as a monolayer membrane, or may be used in combination as a composite membrane. In addition, the microporous membrane may contain appropriate amounts of additives such as various plasticizers, antioxidants and flame retardants.
Moreover, it can be used without a separator if the insulation between the positive electrode and the negative electrode can be ensured.

In the above embodiment, the first insulating layer and the second insulating layer are formed on the positive electrode, but each insulating layer may be formed on the negative electrode. Also, an insulating layer may be formed on both the positive electrode and the negative electrode.
In the above embodiment, the first insulating layer is formed by the wet coating method and the second insulating layer is formed by the dry coating method, but the present invention is not limited to this. Both the first insulating layer and the second insulating layer may be formed by a wet coating method, or both the first insulating layer and the second insulating layer may be formed by a dry coating method.

10 collector foil 20 mixture layer 30 first insulating layer 31 first insulating particles 40 second insulating layer 41 second insulating particles

Claims (6)

A current collector foil and a mixture layer formed on the current collector foil,
The mixture layer has a flat portion and an inclined portion,
At least part of the inclined portion is covered with a first insulating layer containing first insulating particles,
At least part of the planar portion is covered with a second insulating layer containing second insulating particles,
The electrode, wherein the average particle size of the first insulating particles is smaller than the average particle size of the second insulating particles. In the vicinity of a boundary between a mixture layer forming region of the current collector foil where the mixture layer is formed and a mixture layer non-formation region of the current collector foil where the mixture layer is not formed, the current collector 2. The electrode of claim 1, wherein at least a portion of the foil is covered with said first insulating layer. 3. The electrode according to claim 1, wherein said first insulating particles have an average particle size of less than 1.8 [mu]m. 4. The electrode according to claim 1, wherein said second insulating particles have an average particle size of 1.8 [mu]m or more. A method for manufacturing the electrode according to any one of claims 1 to 4,
A method of manufacturing an electrode, comprising forming the second insulating layer by a dry coating method. A nonaqueous electrolyte secondary battery comprising the electrode according to claim 1 .

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