JP7013781B2 - Electrodes, electrode manufacturing methods and power storage elements - Google Patents

Description

The present invention relates to an electrode, a method for manufacturing the electrode, and a power 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 may be used as a method for enhancing the safety thereof. By providing the insulating layer, the insulating property between the positive and negative electrodes is ensured even when the separator shrinks or breaks. More specifically, with respect to the current collector foil and the electrode having the mixture layer provided on the current collector foil, in order to prevent a short circuit at the electrode end, the end of the mixture layer and the current collector foil are insulated. Also known is a method of coating (overcoating) the surface of the mixture layer of at least one electrode with an insulating layer in order to prevent short-circuiting of the mixture layer between the positive electrode and the negative electrode. There is.

Republished Patent WO2010 / 116533A Japanese Unexamined Patent Publication No. 2016-22507

Usually, the insulating layer is composed of insulating particles. When forming such an insulating layer, if the particle size of the insulating particles is increased in order to improve the battery performance due to the permeability of the electrolytic solution to the insulating layer, there is a risk of metal contamination invading the end of the mixture layer. It is difficult to maintain the battery performance and prevent the intrusion of metal contamination at the same time.

The electrode of the present invention includes a current collector foil and a mixture layer formed on the current collector foil, and at least a part of an end portion of the mixture layer is a first insulation containing first insulating particles. Covered with a layer, at least a part of the flat surface portion of the mixture layer is covered with a second insulating layer containing the second insulating particles, and the average particle diameter of the first insulating particles is that of the second insulating particles. It is smaller than the average particle size.

According to the present invention, by forming an insulating layer using insulating particles having different average particle diameters at the end of the mixture layer and the flat surface of the mixture layer, the metal can be suppressed from deteriorating the battery performance. It is possible to provide an electrode capable of preventing the invasion of contamination.

It is the schematic sectional drawing of the electrode by one Embodiment of this invention. FIG. 3 is a schematic partial cross-sectional view of an electrode according to one embodiment of the present invention. It is a partially broken perspective view which shows the schematic structure of the non-aqueous electrolyte secondary battery by one Embodiment of this invention.

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

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

In the present specification, the flat surface 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 portion 21 of the mixture layer 20 is an inclined portion of the mixture layer 20, and is a portion where the thickness of the mixture layer is gradually smaller than that of the flat portion at both ends of the flat portion. .. FIG. 2A 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 are attached to the entire end portion 21 (inclined portion) of the mixture layer 20 to form the first insulating layer. FIG. 2B is a schematic partial cross-sectional view showing the end of the mixture layer of the electrode according to another embodiment of the present invention. In this embodiment, the first insulating particles 31 are attached to a part of the end portion 21 (inclined portion) of the mixture layer 20 to form the first insulating layer. FIG. 2C is a schematic partial cross-sectional view showing the end of the mixture layer of the electrode according to still another embodiment of the present invention. In this embodiment, the first insulating particles 31 adhere to the vicinity of the end portion 21 (inclined portion) of the mixture layer 20 and the peripheral portion of the flat surface portion 22 of the mixture layer 20, and the first insulating layer is formed. ing. As described above, the second insulating layer is attached to at least a part of the flat surface portion 22, but as shown in FIG. 2B, the second insulating layer is at least one of the end portions 21. It may also adhere to the part. Further, as illustrated in FIG. 2B, the first insulating layer and the second insulating layer may overlap each other. Since the insulating layer of No. 1 and the insulating layer of the second are overlapped with each other, the entire surface of the mixture can be surely covered with the insulating layer . In one embodiment, the first insulating layer and the second insulating layer overlap each other at the end of the mixture layer. By overlapping at the end of the mixture layer, which is thinner than the flat surface of the mixture layer, it is possible to prevent the electrode from becoming thick. Preferably, in the overlapping portion, the second insulating layer is arranged on the first insulating layer. The term "near the periphery of the flat surface portion" means a region within 5 mm (preferably within 2 mm) from the boundary between the flat surface portion and the inclined portion.

If the non-aqueous electrolyte secondary battery is configured by using the electrode of the present invention provided with an insulating layer, the insulating property between the positive and negative electrodes can be ensured even when the separator shrinks or the film breaks. In the present invention, by using the first insulating particles having a relatively small particle diameter, the gap between the insulating particles can be narrowed to form the first insulating layer. As a result, the first insulating layer effectively prevents contamination (particularly, metal contamination) from entering the mixture layer. On the other hand, by using the second insulating particles having a relatively large particle diameter, the gap between the insulating particles can be widened to form the second insulating layer. As a result, in the second insulating layer, excellent permeability of the electrolytic solution can be obtained. In the present invention, in order to form a first insulating layer in which the first insulating particles are densely present at the end of the mixture layer having a high possibility of contamination penetration, and to dispose of the first insulating layer facing the counter electrode. By forming a second insulating layer having excellent electrolytic solution permeability on the surface of the mixture layer where contamination is difficult to invade, an electrode capable of preventing metal contamination from invading while suppressing deterioration of battery performance can be obtained. Can be done.

In one embodiment, as shown in FIG. 1, the electrode 101 has a mixture layer forming region 11 in which the mixture layer 20 is formed and a combination 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 a part of the current collector foil 10 (mixture layer non-forming region) is the first insulating layer. It is covered with 30. In other words, in this embodiment, the first insulating layer 30 continuously covers at least a part of the end portion 21 of the mixture layer 20 and at least a part of the current collector foil 10. By having the first insulating layer 30 in such a configuration, the insulating effect and the effect of preventing the invasion of contamination 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 in the range of 2 mm to 10 mm from the vicinity of the boundary between the mixture layer forming region and the mixture layer non-forming region.

The electrode of the present invention is used as a positive electrode or a negative electrode of a non-aqueous electrolyte secondary battery represented by a lithium ion secondary battery. In one embodiment, the electrodes of the invention are used as the positive electrode of a non-aqueous electrolyte secondary battery. If a positive electrode having an insulating layer formed is used, 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 the 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, and even more preferably 0.2 μm to 0.8 μm. Within such a range, the gap between the particles can be reduced, so that the first insulating layer in which contamination is less likely to penetrate can be formed.

In the present specification, the "average particle size" is based on JIS-Z-8815 (2013), and is based on the particle size distribution measured by the laser diffraction / scattering method for a diluted solution obtained by diluting the particles with a solvent. It means a value at which the volume-based integrated distribution calculated in accordance with JIS-Z-8819-2 (2001) is 50%.

In the first insulating particles, D10, D50 and D90 preferably satisfy the relationship of (D90-D10) / D50 ≧ 0.7, and more preferably the relationship of (D90-D10) / D50 ≧ 0.85. Fulfill. Note that D10 means a value at which the volume-based integrated distribution is 10% in the particle size distribution, and D50 means a value at which the volume-based integrated distribution is 50% (that is, the average particle size). D90 means a value at which the volume-based integrated distribution is 90%. The relationship between D10, D50 and D90 above indicates a wide particle size distribution. If such a relationship is satisfied, it becomes easy for small particles to enter between the large particles, and it is possible to form a first insulating layer in which contamination is more difficult to penetrate. The larger the (D90-D10) / D50 of the first insulating particle is, the more preferable it is, but the upper limit thereof is, for example, 1.5.

As the material constituting the first insulating particle, any suitable material can be used as long as it has an insulating property. Examples of the material constituting the first insulating particles include metal oxides such as alumina, boehmite, aluminum hydroxide, silica, zirconia, and magnesia. Further, a siliceate such as silicon carbide, a nitride such as aluminum nitride, or the like may be used. The shape of the first insulating particles is not particularly limited, but is preferably spherical or lumpy from the viewpoint of coatability and permeability of the electrolytic solution. Here, the spherical shape or the lump shape means a shape having an aspect ratio of 1.5 or less.

In one embodiment, the first insulating layer further comprises a first binder. The first binder has a function of binding the first insulating particles to each other, and by using the first binder, it is possible to form a first insulating layer in which the first insulating particles are hard to be detached. ..

As the first binder, any suitable material can be used as long as the effect 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 vinylacetate-based resins, and polyacrylic acids such as polymethylmethacrylate. Examples thereof include imide-based resins such as resins, polyimides and polyamideimides, 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, still more preferably, with respect to 100 parts by weight of the first insulating layer. Is 3 parts by weight to 10 parts by weight. Within such a range, it is possible to form a first insulating layer in which the first insulating particles are difficult to be detached. When the first insulating layer is formed by the dry coating method described later, the content of the first binder shall be 10 parts by weight to 30 parts by weight with respect to 100 parts by weight of the first insulating layer. Is preferable.

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

C. Second Insulating Layer As described above, the second insulating layer is composed of the second insulating particles. Preferably, the second insulating layer further comprises a second binder. The second binder has a function of binding the second insulating particles to each other, and by using the second binder, it is possible to form a second insulating layer in which the second insulating particles are difficult to be detached. ..

The average particle size of the second insulating particles is preferably 1.8 μm or more, more preferably 1.8 μm to 5.0 μm, and particularly preferably 1.8 μm to 3.5 μm. Within such a range, the gap between the insulating particles can be increased, so that a second insulating layer having excellent permeability of the electrolytic solution can be formed. 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 diameter of the second insulating particle to the average particle diameter of the first insulating particle (average particle diameter of the second insulating particle / average particle diameter of the first insulating particle) is preferably 1. It is 2 to 8, and more preferably 1.5 to 6. Within such a range, it is possible to obtain an electrode in which the improvement of the permeability of the electrolytic solution into the mixture layer and the prevention of metal contamination invasion into the mixture layer are highly compatible.

In the second insulating particle, D10, D50 and D90 preferably satisfy the relationship of (D90-D10) /D50≤0.8, and more preferably the relationship of (D90-D10) /D50≤0.7. Fulfill. The above relationship of D10, D50 and D90 indicates that the particle size distribution is narrow and the particle diameters are uniform. Since the particles have 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 significantly excellent electrolytic solution permeability is formed. be able to. The smaller the (D90-D10) / D50 of the second insulating particle is, the more preferable it is, but the lower limit thereof is, for example, 0.5.

As the material constituting the second insulating particle, any suitable material can be used as long as it has an insulating property. As the material constituting the second insulating particle, for example, the material described in the above item B can be used.

As the material constituting the second binder, any suitable material can be used as long as the effect of the present invention can be obtained. As the material constituting the second binder, for example, the material described in the above item 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, and even more, with respect to 100 parts by weight of the second insulating layer. It is preferably 3 parts by weight to 15 parts by weight. Within such a range, it is possible to form a second insulating layer in which the second insulating particles are difficult to be detached. When the second insulating layer is formed by the dry coating method described later, the content of the second binder is preferably 10 parts by weight to 30 parts by weight with respect to 100 parts by weight of the second insulating layer.

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

The ratio (thickness / average particle diameter) of the thickness of the second insulating layer to the average particle diameter of the second insulating particles is preferably 1 to 8, more preferably 1.2 to 5, and even more preferably 1.2 to 5. It is 1.2 to 3. Within such a range, it is possible to form a second insulating layer having a small adverse effect on battery performance and having excellent insulating properties. Further, by using the dry coating method described later, it is possible to reduce the thickness ratio of the second insulating particles to the average particle size while preventing the resistance of the mixture layer from increasing. Since the mass of the 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% with respect to the total area of the flat surface portion 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 having a small adverse effect on battery performance and having excellent insulating properties.

D. Current collector foil As the current collector foil, any suitable current collector foil commonly used for non-aqueous electrolyte secondary batteries can be used. When the electrode is configured as a negative electrode, a metal foil such as a copper foil is used as the current collector foil. When the electrode is configured as a positive electrode, a metal foil such as an aluminum foil is used as the current 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 occluding and releasing lithium ions. Examples of the negative electrode active material include graphite (scaly graphite, scaly graphite, earthy graphite, artificial graphite), coke, carbon material of activated carbon, aluminum, alloy of silicon and lithium, metallic lithium, LiFe ₂ O ₃ , and the like. Examples thereof include metal oxides such as WO ₂ , MoO ₂ , 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 occluding and releasing lithium ions. The positive electrode active material is represented by the composition formulas Li _x MO ₂ , Li _y M ₂ O ₄ , and Na _x MO ₂ (where M is one or more transition metals, 0 ≦ x ≦ 1, 0 ≦ y ≦ 2). Transitional metal oxides that occlude and release lithium, such as composite oxides, tunneled or layered metal chalcogens, and metal oxides, can be used. Specific examples thereof include LiCoO ₂ , LiNiO ₂ , LiNi _1/2 Mn _1/2 O ₂ , LiNi _1/3 Mn _1/3 Co _1/3 O ₂ , LiCo _x Ni _1-x O ₂ , and LiMn ₂ O. ₄ , Li ₂ Mn ₂ O ₄ and the like can be mentioned.

The mixture layer may further contain additives such as binders, conductive agents, thickeners, fillers and the like. Examples of the binder include polyvinylidene fluoride, styrene butadiene rubber, carboxymethyl cellulose, polytetrafluoroethylene, polyethylene, polypropylene, polyacrylonitrile, ethylene-propylene-dienter polymer (EPDM), sulfonated EPDM, fluororubber, and the like. Examples thereof include a vinylidene fluoride-hexafluoropropylene copolymer. Examples of the conductive agent include carbon materials such as acetylene black and carbon black.

F. Method of manufacturing the electrode In the electrode, the first insulating particles and the second insulating particles are coated on a laminate composed of a current collector foil and a mixture layer together with a binder, and the first insulating layer and the first insulating layer and the second insulating particles are coated with a binder. It can be manufactured by forming a second insulating layer. The first insulating particle is applied to the end portion (inclined portion) of the mixture layer. In one embodiment, the first insulating particle is coated near the boundary between the mixture layer forming region and the mixture layer non-forming region, and as a result, a part and a collection of the end portion of the mixture layer. The first insulating layer is formed on at least a part of the electric foil (the region where the mixture layer is not formed). Further, the first insulating particles may be coated so that the first insulating particles adhere to the vicinity of the periphery of the flat surface portion of the mixture layer. The second insulating particle is applied to the flat surface portion of the mixture layer facing the counter electrode. The second insulating layer is preferably applied to the entire flat surface 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. Further, the second insulating particles may be coated so as to adhere to a part of the end portion of the mixture layer.

It is preferable that the first insulating particles are applied to the end portion of the mixture layer, and then the second insulating particles are applied to the flat surface portion of the mixture layer. By forming the first insulating layer and the second insulating layer in this way, the first insulating particles and the mixture layer come into contact with each other. As a result, the first insulating particles and the binder easily enter the unevenness of the surface of the mixture layer and block some of the active material particles, so that the invasion of contamination can be further prevented.

Any suitable method can be adopted as the method for 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 (for example, NMP) is applied, or a dry method in which insulating particles and binder particles are combined and coated without using a solvent. By a coating method or the like, insulating particles and a binder can be applied to a laminate composed of a current collector foil and a mixture layer to form an insulating layer. Here, the 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 permeates the end portion of the mixture layer together with the solvent, and the active material particles can be closed with the binder. Therefore, it is possible to further prevent the intrusion of contamination. On the other hand, by forming the second insulating layer by the dry coating method, it is possible to prevent the binder from penetrating between the active material particles in the flat surface portion of the mixture layer. Therefore, it is possible to prevent the resistance from increasing without reducing the permeability of the electrolytic solution into the mixture layer. Further, if the dry coating method is used, insulating particles having a large particle size can be uniformly and thinly coated. Therefore, the dry coating method is a second method composed of a second insulating particle having a relatively large particle size. Suitable for forming an insulating layer.

It is preferable that the first insulating layer and the second insulating layer overlap at the end of the mixture layer. 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. Further, by overlapping at the end portion of the mixture layer having a thickness smaller than the flat surface portion of the mixture layer, it is possible to prevent the electrode from becoming thick.

One embodiment of the dry coating method is electrostatic coating in which a composite of insulating particles and binder particles is attached to a laminate composed of a current collector foil and a mixture layer by electrostatic attraction. More specifically, (i) a step of mixing insulating particles and particulate binders (hereinafter, also referred to as binder particles) to obtain a composite, and (ii) electrostatic coating to obtain the composite. An insulating layer is formed through a step of adhering to a laminate composed of a current 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 complex (complex composed of the second insulating particles and the second binder particles) is a mixture layer. Attached to the flat surface (and part of the end if necessary).

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

In electrostatic coating, a laminate composed of the current collector foil and the mixture layer and a composite of insulating particles and binder particles are put into a coating booth equipped with an electrode for electrostatic coating. These laminates and composites are charged, and the composite is adhered to the laminate composed of the current collector foil and the mixture layer by electrostatic attraction. At this time, it is preferable to prevent the complex from adhering to a portion where the formation of the insulating layer is not desired by using a mask or the like. For example, it is possible to prevent the second insulating layer from being formed on the current collector foil (mixture layer non-formation region) by a method such as masking the current collector foil (mixture layer non-formation region).

After the electrostatic coating, the binder particles are fused by heating the laminate to which the composite is attached, and the insulating particles and the binder particles are immobilized. The heating temperature can be any suitable temperature depending on the type of binder particles. Examples of the heating method include a method of putting the laminated body to which the complex is attached into a heating furnace, a method of heating the laminated body to which the complex is attached while pressing the heating roll, and the like.

An example of an embodiment relating to a method for manufacturing an electrode is shown below.
1. 1. A slurry-like positive electrode mixture layer forming material is produced by mixing a positive electrode active material, a binder for the positive electrode mixture layer, a conductive auxiliary agent, and a solvent in a predetermined ratio. The positive electrode mixture layer forming material is applied on the band-shaped current collector foil in the strip-shaped longitudinal direction. In this coating, the positive electrode mixture layer forming material is coated on the current collector foil with a width narrower than the width of the current collector foil. The positive electrode mixture layer forming material is heated to volatilize the solvent to form the positive electrode mixture layer.
2. 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 in the vicinity of 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 a part of the current collector foil and a part of the end portion 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 applied. The solvent may be volatilized at the same time.
3. 3. By mixing the second insulating particles and the particles of the second binder by mechanofusion or the like, a complex in which the second binder particles are adhered to the surface of the second insulating particles is formed. The composite is adhered to the flat surface portion of the positive electrode mixture layer by the above electrostatic coating. A second insulating layer is formed by heating after the adhesion.

G. Non-aqueous electrolyte secondary battery FIG. 3 is a partially cutaway perspective view showing a schematic configuration of a non-aqueous electrolyte secondary battery according to one embodiment of the present invention. The 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, the non-aqueous electrolyte secondary battery 110 includes a power generation element 111 in which a positive electrode 100 and a negative electrode 200 are wound around the separator 300. The power generation element 111 is housed in the battery case 112 in a state where the separator 300 is impregnated with a non-aqueous electrolyte. The battery case 112 is, for example, a substantially box type having an opening on the upper surface side. The opening is closed by a plate-shaped battery lid 113. The battery lid 113 is provided with a positive electrode terminal 114 and a negative electrode terminal 115. The positive electrode terminal 114 is electrically connected to the positive electrode 100 via the positive electrode lead 116, and the negative electrode terminal 115 is electrically connected to the negative electrode 200 via the negative electrode lead 117. It is connected.

As the non-aqueous electrolyte, any suitable non-aqueous electrolyte is used. Non-aqueous electrolytes include non-aqueous solvents and electrolyte salts. Examples of the non-aqueous solvent include chain carbonates such as ethylmethyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and diphenyl carbonate; ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, styrene carbonate, and the like. And so on. These non-aqueous solvents may be used alone or in combination of two or more. Examples of the electrolyte salt include ionic compounds such as LiPF6, LiPF2 (C2O4) 2, LiPF3 (CF2CF3) 3, LiPF4 (C2O4) , LiClO4, LiBF4, and LiAsF6.

As the separator, for example, a microporous membrane containing a polyolefin resin such as polyethylene or polypropylene as a main component is used. The microporous membrane may be used alone as a single-layer membrane, or a plurality of microporous membranes may be used as a composite membrane in combination. Further, the microporous membrane may contain an appropriate amount of additives such as various plasticizers, antioxidants and flame retardants. Further, if the insulation between the positive electrode and the negative electrode can be ensured, it can be used without a separator.

In the above embodiment, the first insulating layer and the second insulating layer are formed on the positive electrode, but the respective insulating layers may be formed on the negative electrode. Further, 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 a wet coating method, and the second insulating layer is formed by a 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 Current 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 positive electrode mixture layer formed on the current collector foil are provided.
At least a part of the end portion of the positive electrode mixture layer is covered with the first insulating layer containing the first insulating particles.
At least a part of the flat surface portion of the positive electrode mixture layer is covered with the second insulating layer containing the second insulating particles.
An electrode in which 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 the boundary between the positive electrode mixture layer forming region where the positive electrode mixture layer of the current collector foil is formed and the positive electrode mixture layer non-forming region where the positive electrode mixture layer of the current collector foil is not formed. The electrode according to claim 1, wherein at least a part of the current collector foil is covered with the first insulating layer. The electrode according to any one of claims 1 or 2, wherein the average particle diameter of the first insulating particles is less than 1.8 μm. The electrode according to any one of claims 1 to 3, wherein the average particle diameter of the second insulating particle is 1.8 μm or more. The method for manufacturing an electrode according to any one of claims 1 to 4.
A method for manufacturing an electrode, which comprises forming the second insulating layer by a dry coating method. A non-aqueous electrolyte secondary battery comprising the electrode according to any one of claims 1 to 4.

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