Negative electrode and lithium ion secondary battery

Abstract

To provide an insulating layer with excellent insulating properties between a positive electrode and a negative electrode of a lithium ion secondary battery.SOLUTION: A negative electrode 100 for a lithium ion secondary battery includes a negative electrode active material layer 120 including at least a negative electrode active material and a binder on a current collector 110. The negative electrode 100 for a lithium ion secondary battery further includes an insulating layer 300 including at least an insulating material and a binder on a surface of the negative electrode active material layer 120. The binder included in the insulating layer 300 includes at least one kind selected from styrene butadiene rubber, carboxymethyl cellulose, and salts thereof. The binder included in the negative electrode active material layer 120 is at least one kind selected from polyacrylic acid and a salt thereof.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a negative electrode and a lithium ion secondary battery. [Background technology]

[0002] A lithium-ion secondary battery includes a negative electrode, a positive electrode, and a separator interposed between the negative electrode and the positive electrode. Patent Document 1 discloses a nonaqueous secondary battery in which a negative electrode having a negative electrode mixture layer containing a negative electrode active material and a binder, a positive electrode, a separator, and a nonaqueous electrolyte are housed in an exterior body. Patent Document 1 also describes using a porous membrane for the separator, and forming a heat-resistant porous layer containing a heat-resistant inorganic filler on its surface.

[0003] In the structure described in Patent Document 1, the electrodes and the heat-resistant layer on the separator are not integrated, so when the substrate contracts during heat generation, the heat-resistant layer attached to the substrate also moves, and therefore the insulating function between the positive and negative electrodes is not sufficient.

[0004] Patent Document 2 describes a method for producing a lithium ion secondary battery that does not include a separator. The production method described in Patent Document 1 has a laminated structure in which an electrode active material layer and an insulating layer are arranged in this order, and includes applying an active material layer material to at least one surface of an electrode current collector to form a first coating film, applying an insulating layer material on the first coating film to form a second coating film, and then drying the first coating film and the second coating film simultaneously. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-170945 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-147148 Summary of the Invention [Problem to be solved by the invention]

[0006] In the simultaneous drying method, in which an insulating layer material is applied to a first coating to form a second coating, and then the first and second coatings are dried simultaneously, the insulating layer material penetrates into the active material layer material, resulting in the formation of a mixed layer between the active material layer and the insulating layer. The formation of this mixed layer increases the adhesion strength between the active material layer and the insulating layer. However, if the insulating material penetrates too much into the active material, the active material layer may be exposed on the surface of the insulating layer. This reduces the insulating performance of the insulating layer.

[0007] The present invention has been made in consideration of the above circumstances, and its purpose is to improve the adhesion between an active material layer and an insulating layer (high resistance layer) when the insulating layer (high resistance layer) is formed on an active material layer, while preventing the insulating performance of the insulating layer (high resistance layer) from deteriorating. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, each aspect of the present invention employs the following configuration.

[0009] The first aspect relates to a negative electrode for a lithium ion secondary battery. A first negative electrode for a lithium ion secondary battery according to a first aspect of the present invention comprises: On one side of the current collector, A negative electrode for a lithium ion secondary battery, in which a negative electrode active material layer containing at least a negative electrode active material and a binder is formed, the negative electrode active material layer further has an insulating layer containing at least an insulating material and a binder on a first surface thereof, the first surface being the surface opposite to the current collector; the binder contained in the insulating layer contains at least styrene-butadiene rubber and at least one selected from carboxymethyl cellulose and a salt thereof; the binder contained in the negative electrode active material layer is at least one selected from polyacrylic acid and salts thereof, When element mapping is performed on a cross-sectional SEM image of a cross section of the negative electrode using an EDX method, the direction from the first surface of the negative electrode active material layer toward the one surface of the current collector in the negative electrode active material layer is defined as the Z direction, and the maximum value in the Z direction in which an element that is not detected in the negative electrode active material but is detected in the insulating material is defined as Z A and the average thickness of the negative electrode active material layer in the Z direction is Z B When Z A / Z B is less than 11%.

[0010] A second negative electrode for a lithium ion secondary battery according to the first aspect includes: A negative electrode for an all-solid-state lithium-ion secondary battery, On one side of the current collector, A negative electrode for a lithium ion secondary battery, in which a negative electrode active material layer containing at least a negative electrode active material and a binder is formed, the negative electrode active material layer further has a high-resistance layer containing at least a solid electrolyte and a binder on a first surface thereof, the first surface being the surface opposite to the current collector; the binder contained in the high resistance layer contains at least one selected from styrene butadiene rubber and carboxymethyl cellulose and a salt thereof; the binder contained in the negative electrode active material layer is at least one selected from polyacrylic acid and salts thereof, When element mapping is performed on a cross-sectional SEM image of the cross section of the negative electrode using an EDX method, the direction from the first surface of the negative electrode active material layer toward the one surface of the current collector in the negative electrode active material layer is defined as the Z direction, and the maximum value in the Z direction in which an element that is not detected in the negative electrode active material but is detected in the solid electrolyte is defined as Z A and the average thickness of the negative electrode active material layer in the Z direction is Z B When Z A / Z B is less than 11%.

[0011] The second aspect relates to a lithium ion secondary battery. A first lithium-ion secondary battery according to a second aspect includes: A lithium ion secondary battery comprising a positive electrode having a positive electrode active material layer formed on a current collector, a negative electrode, and an electrolyte, The negative electrode is a negative electrode for a lithium ion secondary battery according to the first aspect.

[0012] A second lithium-ion secondary battery according to a second aspect includes: An all-solid-state lithium-ion secondary battery comprising a positive electrode having a positive electrode active material layer formed on a current collector, a negative electrode, and a solid electrolyte, wherein the negative electrode is the negative electrode for the all-solid-state lithium-ion secondary battery according to the first aspect.

[0013] A third aspect relates to a method for producing a negative electrode for a lithium ion secondary battery. A first method for producing a negative electrode for a lithium ion secondary battery according to a third aspect includes: On a sheet-shaped current collector, (A) applying a negative electrode active material slurry containing at least a negative electrode active material and a binder; (B) applying an insulating layer slurry containing at least an insulating material and a binder onto the surface of the negative electrode active material slurry; (C) simultaneously drying the slurries applied in steps (A) and (B); A method for producing a negative electrode for a lithium ion secondary battery, comprising at least the steps of: the binder contained in the insulating layer slurry contains at least styrene-butadiene rubber and at least one selected from carboxymethyl cellulose and a salt thereof; The binder contained in the negative electrode active material slurry is at least one selected from polyacrylic acid and salts thereof.

[0014] A second method for producing a negative electrode for a lithium ion secondary battery according to a third aspect includes the steps of: A method for manufacturing a negative electrode for an all-solid-state lithium ion secondary battery, comprising: On a sheet-shaped current collector, (A) applying a negative electrode active material slurry containing at least a negative electrode active material and a binder; (B) applying a high-resistance layer slurry containing at least a solid electrolyte and a binder onto the surface of the negative electrode active material slurry; (C) simultaneously drying the slurries applied in steps (A) and (B); A method for producing a negative electrode for an all-solid-state lithium ion secondary battery, comprising at least the following in this order: the binder contained in the high-resistance layer slurry contains at least one selected from styrene-butadiene rubber and carboxymethyl cellulose and its salt; The binder contained in the negative electrode active material slurry is at least one selected from polyacrylic acid and salts thereof.

[0015] A fourth aspect relates to a method for producing a negative electrode sheet for a lithium ion secondary battery. A first method for producing a negative electrode sheet for a lithium ion secondary battery according to a fourth aspect includes: A method for producing a negative electrode sheet for a lithium ion secondary battery by the production method according to a third aspect, comprising: The method includes a step in which a negative electrode active material slurry containing at least a negative electrode active material and a binder, and an insulating layer slurry containing at least an insulating material and a binder are continuously applied to the current collector sheet in the direction in which the current collector sheet is continuously transported.

[0016] A second method for producing a negative electrode sheet for a lithium ion secondary battery according to a fourth aspect includes: A method for producing a negative electrode sheet for an all-solid-state lithium ion secondary battery by the production method according to a third aspect, comprising: The method includes a step in which a negative electrode active material slurry containing at least a negative electrode active material and a binder, and a high-resistance layer slurry containing at least a solid electrolyte and a binder are continuously applied in the direction in which the current collector sheet is continuously transported.

[0017] Any combination of the above components, and any transformation of the present invention into a method, device, system, recording medium, computer program, etc., are also valid aspects of the present invention.

[0018] Furthermore, the various components of the present invention do not necessarily have to be independent entities, but may be formed as a single member by multiple components, one component may be formed from multiple components, one component may be part of another component, or part of one component may overlap with part of another component, etc.

[0019] Furthermore, although the method of the present invention describes a number of steps in a sequential order, the order does not limit the order in which the steps are performed. Therefore, when implementing the method of the present invention, the order of the steps can be changed as long as it does not cause any problems in terms of the content.

[0020] Furthermore, the steps of the method of the present invention are not limited to being executed at different times, and therefore, a step may occur while another step is being executed, or the execution timing of a step may partially or completely overlap with the execution timing of another step, etc. [Effects of the Invention]

[0021] According to the above-described aspects of the present invention, it is possible to provide an insulating layer or a high-resistance layer that has excellent insulating properties between the positive electrode and the negative electrode of a lithium ion secondary battery. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a top view of a lithium ion secondary battery according to an embodiment. [Figure 2] 2 is a top view of the laminate, showing the first lead, the second lead, and the exterior material removed from FIG. 1. FIG. [Figure 3] 3 is a cross-sectional view taken along the line AA′ of FIG. 2. [Figure 4] FIG. 2 is a diagram illustrating an apparatus for manufacturing a negative electrode sheet. [Figure 5] 5 is a diagram illustrating a process for producing a negative electrode sheet using the apparatus shown in FIG. 4. FIG. [Figure 6] The results are shown for cross sections of samples of examples or comparative examples. [Figure 7] The results are shown for cross sections of samples of examples or comparative examples. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, like components are designated by like reference numerals, and the description thereof will be omitted as appropriate.

[0024] In this specification, ordinal numbers such as "first," "second," and "third" are used solely to distinguish between similarly named structures, unless otherwise specified, and do not imply any particular characteristics (e.g., order or importance) of the structures.

[0025] Fig. 1 is a top view of a lithium-ion secondary battery 10 according to an embodiment. Fig. 2 is a view in which a first lead 150, a second lead 250, and an exterior material 400 have been removed from Fig. 1. In other words, Fig. 2 is a top view of a laminate 12. Fig. 3 is a cross-sectional view taken along line AA' in Fig. 2.

[0026] 1 to 3, the first direction X indicates the length direction of the lithium ion secondary battery 10 (laminated body 12). The negative direction of the first direction X (the direction indicated by the arrow indicating the first direction X) is the direction from the first lead 150 to the second lead 250. The negative direction of the first direction X (the direction opposite to the direction indicated by the arrow indicating the first direction X) is the direction from the second lead 250 to the first lead 150. The second direction Y indicates the width direction of the lithium ion secondary battery 10 (laminated body 12). The negative direction of the second direction Y (the direction indicated by the arrow indicating the second direction Y) is the leftward direction of the lithium ion secondary battery 10 (laminated body 12) when viewed from the positive direction of the first direction X. The positive direction of the second direction Y (the direction opposite to the direction indicated by the arrow indicating the second direction Y) is the rightward direction of the lithium ion secondary battery 10 (laminated body 12) when viewed from the positive direction of the first direction X. The third direction Z is the thickness (height) direction of the lithium ion secondary battery 10 (laminated body 12). The negative direction of the third direction Z (the direction indicated by the arrow indicating the third direction Z) is the upward direction of the lithium ion secondary battery 10 (laminated body 12). The positive direction of the third direction Z (the direction opposite to the direction indicated by the arrow indicating the third direction Z) is the downward direction of the lithium ion secondary battery 10 (laminated body 12).

[0027] The negative electrode 100 according to this embodiment will be outlined with reference to FIG. The negative electrode 100 has a negative electrode active material layer 120 formed on a negative electrode current collector 110, the negative electrode active material layer 120 containing at least a negative electrode active material and a binder. Furthermore, an insulating layer 300 containing at least an insulating material and a binder is formed on the surface of the negative electrode active material layer 120. The binder contained in the insulating layer 300 includes at least one selected from styrene-butadiene rubber and carboxymethyl cellulose and its salts. The binder contained in the negative electrode active material layer 120 is at least one selected from polyacrylic acid and its salts.

[0028] The lithium ion secondary battery 10 will be described with reference to FIGS.

[0029] The lithium ion secondary battery 10 includes a laminate 12, a first lead 150, a second lead 250, and an exterior material 400.

[0030] The first lead 150 is electrically connected to the negative electrode 100 (for example, FIG. 3). The first lead 150 may be made of, for example, copper or a copper alloy, or a nickel-plated copper or copper alloy.

[0031] The second lead 250 is electrically connected to the positive electrode 200 (see, for example, FIG. 3). The second lead 250 may be made of, for example, aluminum or an aluminum alloy.

[0032] The exterior packaging material 400 has a rectangular shape with four sides. In this embodiment, the second lead 250 is provided on a side of the exterior packaging material 400 that is located on the positive side in the first direction X, and the first lead 150 is provided on a side of the exterior packaging material 400 that is located on the negative side in the first direction X. However, the second lead 250 and the first lead 150 may be provided on a common side of the exterior packaging material 400 (for example, a side that is located on the negative or positive side in the first direction X).

[0033] Each cell of the lithium ion secondary battery 10 includes a negative electrode 100, a positive electrode 200, and an electrolyte (not shown). The electrolyte may be in a liquid, gel, or solid state. In this embodiment, the electrolyte of the lithium ion secondary battery 10 is in a liquid state and will be described as an "electrolytic solution." A manufacturing process when a solid electrolyte is used will be described later. The exterior material 400 accommodates the laminate 12 together with an electrolyte solution (not shown).

[0034] The exterior material 400 includes, for example, a heat-sealable resin layer and a barrier layer, and may be, for example, a laminated film including a heat-sealable resin layer and a barrier layer.

[0035] The resin material forming the heat-sealable resin layer may be, for example, polyethylene (PE), polypropylene, nylon, polyethylene terephthalate (PET), etc. The thickness of the heat-sealable resin layer is, for example, 20 μm or more and 200 μm or less.

[0036] The barrier layer has barrier properties, such as preventing leakage of the electrolyte or intrusion of moisture from the outside, and may be formed of metals such as stainless steel (SUS) foil, aluminum foil, aluminum alloy foil, copper foil, titanium foil, etc. The thickness of the barrier layer is, for example, 10 μm or more and 100 μm or less.

[0037] The heat-sealable resin layer of the laminated film may be one layer or two or more layers, and similarly, the barrier layer of the laminated film may be one layer or two or more layers.

[0038] The electrolyte solution is, for example, a non-aqueous electrolyte solution, which may contain a lithium salt and a solvent that dissolves the lithium salt.

[0039] Lithium salts include, for example, LiClO4, LiBF6, LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiB 10 Cl 10 , LiAlCl4, LiCl, LiBr, LiB(C2H5)4, CF3SO3Li, CH3SO3Li, LiC4F9SO3, Li(CF3SO2)2N, lithium carboxylate of lower fatty acids, etc.

[0040] Examples of solvents that dissolve lithium salts include carbonates such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), and vinylene carbonate (VC); lactones such as γ-butyrolactone and γ-valerolactone; ethers such as trimethoxymethane, 1,2-dimethoxyethane, diethyl ether, tetrahydrofuran, and 2-methyltetrahydrofuran; and sulfonates such as dimethyl sulfoxide. Examples of suitable solvents include sulfoxides; oxolanes such as 1,3-dioxolane and 4-methyl-1,3-dioxolane; nitrogen-containing solvents such as acetonitrile, nitromethane, formamide, and dimethylformamide; organic acid esters such as methyl formate, methyl acetate, ethyl acetate, butyl acetate, methyl propionate, and ethyl propionate; phosphate triesters and diglymes; triglymes; sulfolanes such as sulfolane and methylsulfolane; oxazolidinones such as 3-methyl-2-oxazolidinone; and sultones such as 1,3-propane sultone, 1,4-butane sultone, and naphthasultone. These substances may be used alone or in combination.

[0041] The laminate 12 will be described with reference to FIG.

[0042] The laminate 12 has a plurality of negative electrodes 100 and a plurality of positive electrodes 200 coated with an insulating layer 300. The negative electrodes 100 and positive electrodes 200 coated with the insulating layer 300 are alternately stacked in the third direction Z. Each insulating layer 300 is located between a positive electrode 200 and a negative electrode 100 adjacent to each other in the third direction Z. However, the laminate 12 may have only one negative electrode 100 and only one positive electrode 200 coated with the insulating layer 300.

[0043] However, the laminate 12 may also be configured to include a common polyolefin-based film separator. In this case, the laminate 12 may have at least one of the following structures: a "laminated" structure (which may be a single layer) in which the negative electrode 100 and the positive electrode 200 are "laminated" with a separator interposed therebetween; a "wound" structure in which the negative electrode 100 and the positive electrode 200 are stacked with a long separator interposed and wound into a roll; and a "zigzag" structure in which the negative electrode 100 and the positive electrode 200 are zigzag-folded with a long separator interposed therebetween. Furthermore, the laminate 12 may have a structure in which a plurality of "laminated" laminates 12 are further wound with a long separator or zigzag-folded.

[0044] As an example, in the above-mentioned "zigzag" structure, the separator may be folded back along the first direction X on the outside in the first direction X of the negative electrode 100 or the positive electrode 200 to which the insulating layer 300 is applied, and may be extended in a zigzag manner so as to pass between the negative electrode 100 and the positive electrode 200 when they are adjacent to each other.

[0045] The negative electrode 100 will now be described in detail. The negative electrode 100 includes a negative electrode current collector 110 and a negative electrode active material layer 120.

[0046] The negative electrode current collector 110 of the negative electrode 100 has a first surface 112 and a second surface 114. The first surface 112 of the negative electrode current collector 110 is the upper surface of the negative electrode current collector 110. The second surface 114 of the negative electrode current collector 110 is located opposite the first surface 112 of the negative electrode current collector 110 and is the lower surface of the negative electrode current collector 110.

[0047] An anode active material layer 120 is located on the first surface 112 of the anode current collector 110. Another anode active material layer 120 is located on the second surface 114 of the anode current collector 110. However, the anode active material layer 120 may be located on only one of the first surface 112 and the second surface 114 of the anode current collector 110.

[0048] The end portion on the negative direction side of the first direction X of the negative electrode current collector 110 is connected to the first lead 150 (FIG. 1). For example, in the third direction Z, when the end portion on the negative direction side of the first direction X of the negative electrode current collector 110 and the first lead 150 are displaced, the end portion on the negative direction side of the first direction X of the negative electrode current collector 110 may be bent toward the first lead 150.

[0049] The negative electrode current collector 110 may be formed of, for example, copper, stainless steel, nickel, titanium, or an alloy thereof. The shape of the negative electrode current collector 110 may be, for example, a foil, a flat plate, or a mesh. The thickness (in the third direction Z) of the negative electrode current collector 110 in the third direction Z is, for example, 1 μm or more and 50 μm or less.

[0050] The negative electrode active material layer 120 contains a negative electrode active material and a binder resin. The negative electrode active material layer 120 may further contain a conductive assistant as needed.

[0051] The negative electrode active material is not particularly limited as long as it is a normal negative electrode active material that can be used for the negative electrode 100 of the lithium ion secondary battery 10. For example, carbon materials such as graphite that occludes lithium, amorphous carbon, diamond-like carbon, fullerene, carbon nanotubes, and carbon nanohorns; lithium-based metal materials such as lithium metal and lithium alloys; Si-based materials such as Si, SiO2, SiOx (0 < x ≤ 2), and Si-containing composite materials; and conductive polymer materials such as polyacene, polyacetylene, and polypyrrole. The negative electrode active material may be used alone or in combination of two or more.

[0052] The negative electrode active material layer 120 contains, for example, 90 parts by mass or more and 99 parts by mass or less of the negative electrode active material with respect to 100 parts by mass of the total mass of the negative electrode active material layer 120.

[0053] The average particle size of the negative electrode active material is preferably 1 μm or more, and more preferably 2 μm or more, from the viewpoint of suppressing side reactions during charge and discharge and suppressing a decrease in charge and discharge efficiency, and is preferably 100 μm or less, and more preferably 50 μm or less, from the viewpoint of input / output characteristics and the production of the negative electrode 100 (such as the smoothness of the surface of the negative electrode 100). Here, the average particle size refers to the particle size at 50% of the cumulative value (median diameter: D50) in the particle size distribution (volume basis) determined by a laser diffraction scattering method.

[0054] The density of the negative electrode active material layer 120 is, for example, 1.2 g / cm 3 More than 2.0g / cm 3 The following is the result.

[0055] The thickness (in the third direction Z) of the negative electrode active material layer 120 on one of the two surfaces (the first surface 112 and the second surface 114) of the negative electrode current collector 110 can be determined appropriately. The thickness is, for example, 80 μm or less.

[0056] The total thickness (in the third direction Z) of the negative electrode active material layer 120 on both surfaces (the first surface 112 and the second surface 114) of the negative electrode current collector 110 can be determined appropriately. The thickness is, for example, 160 μm or less.

[0057] When water is used as a solvent for obtaining a slurry, the binder resin contained in the negative electrode active material layer 120 can be, for example, a rubber-based binder (e.g., SBR (styrene-butadiene rubber)) or an acrylic-based binder resin. Such an aqueous binder resin may be in the form of an emulsion. When water is used as a solvent, it is preferable to use an aqueous binder in combination with a thickener such as CMC (carboxymethyl cellulose).

[0058] The amount of binder resin contained in the negative electrode active material layer 120 can be determined appropriately. The negative electrode active material layer 120 contains, for example, 1.0 parts by mass or more and 10.0 parts by mass or less of the binder resin, and more preferably 3 parts by mass or more and 6 parts by mass or less of the binder resin, relative to 100 parts by mass of the total mass of the negative electrode active material layer 120.

[0059] Of the total weight of solid materials constituting the negative electrode active material layer 120, the total weight of polyacrylic acid and its salts among the binders of polyacrylic acid and its salts contained in the negative electrode active material layer 120 is 3% by weight or more and 6% by weight or less.

[0060] The positive electrode 200 will be described in detail below. The positive electrode 200 has a positive electrode current collector 210 and a positive electrode active material layer 220.

[0061] The positive electrode current collector 210 of the positive electrode 200 has a third surface 212 and a fourth surface 214. The third surface 212 of the positive electrode current collector 210 is the bottom surface of the positive electrode current collector 210. The fourth surface 214 of the positive electrode current collector 210 is located opposite the third surface 212 of the positive electrode current collector 210 and is the top surface of the positive electrode current collector 210.

[0062] A positive electrode active material layer 220 is located on the third surface 212 of the positive electrode current collector 210. Another positive electrode active material layer 220 is located on the fourth surface 214 of the positive electrode current collector 210. However, the positive electrode active material layer 220 may be located on only one of the third surface 212 and the fourth surface 214 of the positive electrode current collector 210.

[0063] An end of the positive electrode current collector 210 on the positive side in the first direction X is connected to the second lead 250 (FIG. 1). For example, when the end of the positive electrode current collector 210 on the positive side in the first direction X and the second lead 250 are misaligned in the third direction Z, the end of the positive electrode current collector 210 on the positive side in the first direction X may be bent toward the second lead 250.

[0064] The positive electrode current collector 210 may be formed of, for example, aluminum, stainless steel, nickel, titanium, or an alloy thereof. The positive electrode current collector 210 may be in the form of, for example, a foil, a flat plate, or a mesh. The thickness of the positive electrode current collector 210 (in the third direction Z) is, for example, 1 μm or more and 50 μm or less.

[0065] The positive electrode active material layer 220 contains a positive electrode active material, a binder resin, and a conductive additive.

[0066] The positive electrode active material is not particularly limited as long as it is a common positive electrode active material that can be used for the positive electrode 200 of the lithium-ion secondary battery 10. Examples include composite oxides of lithium and transition metals such as lithium-nickel composite oxide, lithium-cobalt composite oxide, lithium-manganese composite oxide, lithium-nickel-manganese composite oxide, lithium-nickel-cobalt composite oxide, lithium-nickel-aluminum composite oxide, lithium-nickel-cobalt-aluminum composite oxide, lithium-nickel-manganese-cobalt composite oxide, lithium-nickel-manganese-aluminum composite oxide, and lithium-nickel-cobalt-manganese-aluminum composite oxide; transition metal sulfides such as TiS2, FeS, and MoS2; MnO, VO, and VO. 13 Examples of suitable positive electrode active materials include transition metal oxides such as TiO2 and olivine-type lithium phosphate. Olivine-type lithium phosphate contains, for example, at least one element selected from the group consisting of Mn, Cr, Co, Cu, Ni, V, Mo, Ti, Zn, Al, Ga, Mg, B, Nb, and Fe, as well as lithium, phosphorus, and oxygen. These compounds may have some elements partially substituted with other elements to improve their properties. Among these, olivine-type lithium iron phosphate, lithium-nickel composite oxide, lithium-cobalt composite oxide, lithium-manganese composite oxide, lithium-nickel-manganese composite oxide, lithium-nickel-cobalt composite oxide, lithium-nickel-aluminum composite oxide, lithium-nickel-cobalt-aluminum composite oxide, lithium-nickel-manganese-cobalt composite oxide, lithium-nickel-manganese-aluminum composite oxide, and lithium-nickel-cobalt-manganese-aluminum composite oxide are preferred. These positive electrode active materials have high working potentials, large capacities, and high energy densities. The positive electrode active material may be used alone or in combination of two or more.

[0067] The positive electrode active material layer 220 contains, for example, 90 parts by mass or more and 99 parts by mass or less of the positive electrode active material with respect to 100 parts by mass of the total mass of the positive electrode active material layer 220.

[0068] The average particle size of the positive electrode active material contained in the positive electrode active material layer 220 is preferably 1 μm or more, and more preferably 2 μm or more, from the viewpoint of suppressing side reactions during charge and discharge and suppressing a decrease in charge and discharge efficiency, and is preferably 100 μm or less, and more preferably 50 μm or less, from the viewpoint of input / output characteristics and the manufacturing of the positive electrode 200 (such as the smoothness of the surface of the positive electrode 200). Here, the average particle size refers to the particle size at 50% of the cumulative value (median diameter: D50) in the particle size distribution (volume basis) determined by a laser diffraction scattering method.

[0069] The density of the positive electrode active material layer 220 is, for example, 2.0 g / cm 3 More than 4.0g / cm 3 The following is the result.

[0070] The thickness (in the third direction Z) of the positive electrode active material layer 220 on one of the two surfaces (the third surface 212 and the fourth surface 214) of the positive electrode current collector 210 can be determined appropriately. The thickness is, for example, 100 μm or less. The total thickness (in the third direction Z) of the positive electrode active material layer 220 on both surfaces (the third surface 212 and the fourth surface 214) of the positive electrode current collector 210 can be determined appropriately. The thickness is, for example, 200 μm or less.

[0071] The binder resin contained in the positive electrode active material layer 220 is, for example, polytetrafluoroethylene (PTFE) or polyvinylidene fluoride (PVDF).

[0072] The amount of binder resin contained in the positive electrode active material layer 220 can be determined appropriately. The positive electrode active material layer 220 contains, for example, 0.1 parts by mass or more and 10.0 parts by mass or less of binder resin with respect to 100 parts by mass of the total mass of the positive electrode active material layer 220.

[0073] The conductive additive contained in the positive electrode active material layer 220 may be, for example, carbon black, ketjen black, acetylene black, natural graphite, artificial graphite, or carbon fibers such as carbon nanotubes. The graphite may be, for example, flake graphite or spherical graphite. These materials may be used alone or in combination.

[0074] The amount of the conductive additive contained in the positive electrode active material layer 220 can be determined appropriately. The positive electrode active material layer 220 contains, for example, 0.01 parts by mass or more and 8.0 parts by mass or less of the conductive additive with respect to 100 parts by mass of the total mass of the positive electrode active material layer 220.

[0075] The positive electrode active material layer 220 may contain a pH adjuster (for example, oxalic acid) as needed to neutralize the alkaline component contained in the positive electrode active material in order to prevent the slurry from gelling or for other reasons.

[0076] The insulating layer 300 will now be described in detail. The insulating layer 300 has a fifth surface 312 and a sixth surface 314. The fifth surface 312 of the insulating layer 300 faces the negative electrode 100. The sixth surface 314 of the insulating layer 300 faces the positive electrode 200.

[0077] The insulating layer 300 has the function of electrically insulating the negative electrode 100 and the positive electrode 200 and allowing ions (for example, lithium ions) to pass through.

[0078] The insulating layer 300 is preferably formed on at least the entire surface 122 of the negative electrode active material layer 120 of the negative electrode 100 that faces the region where the active material layer of the positive electrode 200 is formed.

[0079] The shape of the insulating layer 300 can be determined appropriately depending on the shape of the negative electrode 100 or the positive electrode 200, and can be, for example, rectangular.

[0080] The insulating layer 300 contains at least an insulating material and a binder. The insulating material contained in the insulating layer 300 includes, for example, at least one selected from aluminum oxide (for example, α-alumina), silica, acrylic resin, magnesia, calcia, titania, zirconia, boehmite, and magnesium hydroxide. The binder contained in the insulating layer 300 includes at least one selected from styrene butadiene rubber and carboxymethyl cellulose and salts thereof.

[0081] The insulating material has a particle size distribution in which the cumulative volume of the particle size is 50%, or a D50 particle size of 0.2 μm or more and 0.8 μm or less.

[0082] Of the total weight of the solid materials that make up insulating layer 300, the weight of styrene butadiene rubber contained in insulating layer 300 is 3% by weight or more and 6% by weight or less.

[0083] The thickness of the insulating layer 300 (in the third direction Z) can be determined appropriately, and can be set to, for example, 1.0 μm or more and 45.0 μm or less.

[0084] As shown in Figures 3 and 5, in the lithium ion secondary battery 10, a separator other than the insulating layer 300 formed on the negative electrode active material layer 120 of the negative electrode 100 is not disposed between the positive electrode 200 and the negative electrode 100.

[0085] Fig. 4 is a diagram illustrating an apparatus 500 for manufacturing the negative electrode sheet 100A. Fig. 5 is a diagram illustrating the process of manufacturing the negative electrode sheet 100A using the apparatus 500 shown in Fig. 4.

[0086] In FIG. 4, the apparatus 500 includes a first dispensing head 510, a second dispensing head 512, a first tank 522, a first pump 524, a first valve 526, a second tank 532, a second pump 534, a second valve 536, a first conveying roller 542, a second conveying roller 544, a third conveying roller 546, and a dryer 550.

[0087] The first discharge head 510 and the second discharge head 512 have discharge ports 510a and 512a, respectively. However, the first discharge head 510 and the second discharge head 512 may be configured as a single discharge head. It is sufficient that the single discharge head has at least the discharge ports 510a and 512a.

[0088] 4, the first conveyor roller 542, the second conveyor roller 544, and the third conveyor roller 546 rotate in the direction (clockwise) of the arrows attached to the first conveyor roller 542, the second conveyor roller 544, and the third conveyor roller 546. Therefore, the negative electrode current collector sheet 110A is fed from below to above from the first conveyor roller 542 to the second conveyor roller 544, and is fed from left to right from the second conveyor roller 544 to the third conveyor roller 546.

[0089] An outline of a method for producing the negative electrode sheet 100A according to this embodiment will be described with reference to FIG. This method is (A) applying a negative electrode active material slurry (hereinafter also referred to as a first slurry 120A) containing at least a negative electrode active material and a binder onto a first surface 112 of a negative electrode sheet 100A; (B) applying an insulating layer slurry (hereinafter also referred to as second slurry 130A) containing at least an insulating material and a binder onto the surface 122 of the negative electrode active material layer 120 (first slurry 120A); (C) a step of simultaneously drying first slurry 120A and second slurry 130A applied in step (A) and step (B), at least in this order.

[0090] First, in step (A), the first slurry 120A is applied to the first surface 112 of the negative electrode current collector sheet 110A by wetting and spreading along the first surface 112 of the negative electrode current collector sheet 110A (see FIG. 5(a)).

[0091] Next, in step (B), the second slurry 130A is applied to the surface 122 of the negative electrode active material layer 120 formed by the first slurry 120A applied in step (A) by wetting and spreading along the surface 122 of the negative electrode active material layer 120 (see Figure 5(b)).

[0092] 5(c), a mixed layer 320 of the negative electrode active material layer 120 (first slurry 120A) and the insulating layer 300 (second slurry 130A) is formed at the interface between the negative electrode active material layer 120 and the insulating layer 300. The thickness of this mixed layer 320 is thinner than the thickness of the negative electrode active material layer 120.

[0093] The method according to this embodiment will be described in detail with reference to FIGS.

[0094] The first tank 522 contains a first slurry 120A. The second tank 532 contains a second slurry 130A. The first slurry 120A contained in the first tank 522 is supplied to the discharge head 510 via a first pump 524 and a first valve 526. The second slurry 130A contained in the second tank 532 is supplied to the discharge head 510 via a second pump 534 and a second valve 536.

[0095] The first slurry 120A supplied to the discharge head 510 is discharged from the discharge port 510a of the first discharge head 510 toward the first surface 112 of the negative electrode current collector sheet 110A. The pressure of the first slurry 120A discharged onto the first surface 112 of the negative electrode current collector sheet 110A is adjusted by, for example, a first pump 524. The flow rate of the first slurry 120A discharged onto the first surface 112 of the negative electrode current collector sheet 110A is adjusted by, for example, a first valve 526.

[0096] The second slurry 130A supplied to the discharge head 510 is discharged from a discharge port 512a of the second discharge head 512 toward the first surface 112 of the negative electrode current collector sheet 110A. The pressure of the second slurry 130A discharged onto the first surface 112 of the negative electrode current collector sheet 110A is adjusted by, for example, a second pump 534. The flow rate of the second slurry 130A discharged onto the first surface 112 of the negative electrode current collector sheet 110A is adjusted by, for example, a second valve 536.

[0097] In this embodiment, the first slurry 120A and the second slurry 130A are sequentially discharged from the discharge openings 510a of the first discharge head 510 and the discharge openings 512a of the second discharge head 512, respectively. Therefore, the second slurry 130A further spreads along the upper surface 122 of the negative electrode active material layer 120 formed by the first slurry 120A that spreads along the first surface 112.

[0098] In this embodiment, the first slurry 120A and the second slurry 130A are continuously applied in the direction in which the negative electrode current collector sheet 110A is transported. Therefore, the first slurry 120A and the second slurry 130A applied to the negative electrode current collector sheet 110A are continuously extended along the direction in which the negative electrode current collector sheet 110A is transported.

[0099] In this embodiment, at least the outlets 510a of the first discharge head 510 and the outlets 512a of the second discharge head 512 are arranged to align in the direction in which the negative electrode current collector sheet 110A is transported. The first slurry 120A is discharged from the outlet 510a of the first discharge head 510, and the second slurry 130A is discharged from the outlet 512a of the second discharge head 512.

[0100] The distance between the outlet 510a of the first discharge head 510 and the outlet 512a of the second discharge head 512 can be set appropriately.

[0101] The first slurry 120A contains a solvent and a material that will become the negative electrode active material layer 120. The solvent contained in the first slurry 120A is, for example, water.

[0102] The second slurry 130A contains a solvent and a material that will become the insulating layer 300. The solvent contained in the second slurry 130A is, for example, water.

[0103] The solid content concentration of the first slurry 120A is 40% or more and 80% or less, and the solid content concentration of the second slurry 130A is 20% or more and 80% or less.

[0104] After the first slurry 120A and the second slurry 130A are supplied from the discharge head 510 to the negative electrode current collector sheet 110A, the negative electrode current collector sheet 110A is sent to the dryer 550. As a result, the first slurry 120A and the second slurry 130A are dried by the dryer 550. The first slurry 120A and the second slurry 130A are formed into the negative electrode active material layer 120 and the insulating layer 300, respectively, by drying in the dryer 550.

[0105] 5(c), a mixed layer 320 of the anode active material layer 120 (first slurry 120A) and the insulating layer 300 (second slurry 130A) is formed at the interface between the anode active material layer 120 formed from the first slurry 120A and the insulating layer 300 formed from the second slurry 130A. The mixed layer 320 has a thickness smaller than that of the anode active material layer 120.

[0106] The thickness of the mixed layer 320 is evaluated by the following method. The direction from the surface 122 of the negative electrode active material layer 120 toward the current collector 110 is defined as the Z direction. A scanning electron microscope (SEM) is used to analyze an SEM image of a cross section of the negative electrode 100. The image analysis involves element mapping using energy dispersive X-ray spectroscopy (EDX). The maximum value in the Z direction at which an element is detected in the insulating material but not in the negative electrode active material is defined as Z A The average thickness of the negative electrode active material layer 120 in the Z direction is defined as Z B Let's say. At this time, Z A / Z B is less than 11%.

[0107] Furthermore, the maximum thickness in the Z direction, Z A is preferably 35 μm or less, more preferably 25 μm or less.

[0108] According to this embodiment, the negative electrode 100 has an insulating layer 300 containing at least an insulating material and a binder on the surface 122 of the negative electrode active material layer 120 formed on the first surface 112 of the sheet-like current collector 110. In the negative electrode 100 of this embodiment, the binder contained in the insulating layer 300 includes at least one selected from styrene-butadiene rubber and carboxymethyl cellulose and its salts, and the binder contained in the negative electrode active material layer 120 is at least one selected from polyacrylic acid and its salts. This makes it possible to manufacture a negative electrode 100 in which the negative electrode active material layer 120 and the insulating layer 300 are not excessively mixed together.

[0109] Furthermore, in the case of a sequential drying method in which the insulating layer 300 is applied after the negative electrode active material layer 120 is formed by coating, drying, and pressing, the thin mixed layer 320 is not formed between the negative electrode active material layer 120 and the insulating layer 300. As a result, the peel strength between the negative electrode active material layer 120 and the insulating layer 300 is low, and similarly, the insulating function between the positive electrode and the negative electrode is not sufficient.

[0110] Furthermore, with the sequential drying method, the insulating layer 300 cannot be applied evenly due to the unevenness and wrinkles of the pressed surface to be coated, and the gloss of the surface to be coated makes it difficult to achieve an even coating. As a result, there is a risk that the insulating layer 300 may not completely cover the negative electrode active material layer 120, or that the insulating layer 300 may be applied to areas where it should not be applied.

[0111] Furthermore, in a method in which the insulating layer 300 is applied immediately after the application of the negative electrode active material layer 120 and then dried at the same time, if the solvents used for the slurries of the negative electrode active material layer 120 and the insulating layer 300 are not the same, the mixed layer 320 will not be formed due to low affinity.

[0112] According to the method for producing a negative electrode for a lithium ion secondary battery of this embodiment, the following is formed on the negative electrode current collector sheet 110A: (A) applying a negative electrode active material slurry (first slurry 120A) containing at least a negative electrode active material and a binder; (B) applying an insulating layer slurry (second slurry 130A) containing at least an insulating material and a binder onto the surface 122 of the negative electrode active material layer 120; (C) simultaneously drying the slurries applied in steps (A) and (B); in this order, the problems with the above-mentioned sequential coating and drying method are solved, and when the insulating layer 300 is formed on the negative electrode active material layer 120, the adhesion between the negative electrode active material layer 120 and the insulating layer 300 can be improved while preventing the insulating performance of the insulating layer 300 from deteriorating.

[0113] Furthermore, in the simultaneous drying method, even if the same solvent is used for the slurries of the negative electrode active material layer 120 and the insulating layer 300, if the binders used in the respective slurries are not appropriately combined, the insulating layer slurry (second slurry 130A) may excessively permeate into the negative electrode active material layer 120. According to the manufacturing method of this embodiment, by using an appropriate combination of binders for the respective slurries, it is possible to prevent the insulating layer slurry (second slurry 130A) from excessively permeating into the negative electrode active material layer 120 and to prevent the insulating performance of the insulating layer from deteriorating.

[0114] According to this embodiment, the thickness of the mixed layer 320 of the negative electrode active material layer 120 and the insulating layer 300 formed at the interface between the negative electrode active material layer 120 and the insulating layer 300 is thinner than the thickness of the negative electrode active material layer 120. As described above, according to this embodiment, it is possible to prevent the second slurry 130A forming the insulating layer 300 from excessively permeating into the negative electrode active material layer 120. Furthermore, it is possible to prevent the first slurry 120A forming the negative electrode active material layer 120 from excessively permeating into the insulating layer 300, so that the active material is not exposed on the surface of the insulating layer 300 and the insulating function is not impaired. This makes it possible to properly maintain the insulating function between the positive and negative electrodes of a lithium-ion secondary battery.

[0115] According to this embodiment, the maximum depth Z at which the insulating material is detected in the negative electrode active material layer 120 A is the average thickness of the negative electrode active material layer in the Z direction, B When Z A / Z BSince the ratio is 11% or less, the insulating material does not diffuse excessively into the negative electrode active material layer 120.

[0116] According to this embodiment, the particle size of the insulating material is limited to 0.2 μm or more and 0.8 μm or less. This prevents the problem of insufficient coating when the particle size of the insulating material is too small, and the problem of reduced insulating properties when the particle size is too large due to a lack of particles relative to the film thickness. In other words, this promotes suitable coating and maintains appropriate insulating properties because the particles are contained in an appropriate ratio relative to the film thickness.

[0117] According to this embodiment, by limiting the amount of binder in the insulating layer 300, it is possible to solve the problem of poor adhesion caused by an excessively small amount of binder. In addition, it is possible to solve the problem that a large amount of binder reduces the voids in the insulating layer, inhibiting the movement of lithium salt between the positive and negative electrodes and increasing the resistance of the battery.

[0118] According to this embodiment, by limiting the amount of the binder in the negative electrode active material layer 120, a sufficient amount of negative electrode active material is ensured, and since there is no excessive amount of binder with high electrical resistance, an electrode with high capacity and high output can be obtained.

[0119] According to this embodiment, the insulating layer 300 having the function of a separator is formed on the negative electrode active material layer 120, eliminating the need for a separator disposed between the positive electrode 200 and the negative electrode 100. This allows the lithium ion secondary battery to be made thinner, and also prevents short circuits between the positive and negative electrodes of the lithium ion secondary battery.

[0120] Although the embodiments of the present invention have been described above with reference to the drawings, these are merely examples of the present invention, and various other configurations can also be adopted. For example, in the above embodiment, the battery cell is described as containing an electrolytic solution. A battery cell with a gel-like electrolyte can also be manufactured using the same process as in the embodiment. On the other hand, in the case of an all-solid-state battery with a solid electrolyte, the manufacturing method of the negative electrode 100 is as described below.

[0121] In step (A), a negative electrode active material slurry (first slurry 120A) containing at least a negative electrode active material, a binder, and a solid electrolyte is applied. The solid electrolyte is, for example, Li7La3Zr2O 12 (LLZ). In step (B), a high-resistance layer slurry (second slurry 130A) containing at least a solid electrolyte and a binder is applied to the surface 122 of the negative electrode active material layer 120. The solid electrolyte is, for example, Li7La3Zr2O 12 (LLZ). Then, in step (C), the slurries applied in steps (A) and (B) are simultaneously dried.

[0122] As described above, in the case of batteries other than all-solid-state batteries, the insulating material contained in insulating layer 300 includes, for example, at least one selected from aluminum oxide (e.g., α-alumina), silica, acrylic resin, magnesia, calcia, titania, zirconia, boehmite, and magnesium hydroxide. On the other hand, in the case of all-solid-state batteries, the high-resistance layer (high-resistance layer slurry) is a solid electrolyte and does not necessarily include the insulating material contained in insulating layer 300. In other words, in the case of all-solid-state batteries, it is sufficient that the high-resistance layer (high-resistance layer slurry) includes at least a solid electrolyte. [Example]

[0123] Table 1 shows the fabrication conditions and evaluation results of the negative electrodes 100 of Examples 1 to 11. Details of the fabrication conditions for the samples are explained below. [Table 1]

[0124] <Production method and conditions> The negative electrode active material constituting the negative electrode active material layer 120 was natural graphite coated with amorphous graphite manufactured by Hitachi Chemical Co., Ltd. The negative electrode active material layer 120 contained a conductive additive, and carbon black was used as the conductive additive. In all Examples and Comparative Examples, the carbon black C65 content was 0.4 wt % of the total weight of the solid materials constituting the negative electrode active material layer 120.

[0125] The binder constituting the negative electrode active material layer 120 was polyacrylic acid (PAA) Aquacharge manufactured by Sumitomo Seika Chemicals Co., Ltd.

[0126] The insulating material (filler) constituting the insulating layer 300 was either alumina, acrylic resin (Poly Methyl Methacrylate (PMMA)), or silica. The alumina used was Alumina AKP-3000 manufactured by Sumitomo Chemical Co., Ltd. The acrylic resin (PMMA) used was MX-80H3wT (average particle size 0.8 μm, high cross-linking) from the MX series of cross-linked acrylic monodisperse particles manufactured by Soken Chemical & Engineering Co., Ltd. The silica used was Super Fine Powder (submicron silica) SFP-20M (0.3 μm) or SFP-30M (0.6 μm) manufactured by Denka Co., Ltd.

[0127] The binder used to form the insulating layer 300 was a mixture of sodium carboxymethyl cellulose (CMC-Na) and styrene-butadiene rubber (SBR). The CMC used was MAC-350HC from the MAC series of Sunrose (registered trademark) manufactured by Nippon Paper Industries Co., Ltd. The SBR used was BM-451B manufactured by Zeon Corporation.

[0128] The viscosity of each slurry was 8000±2000 mPa·s (conditions: B-type viscometer, 20°C, shear rate 2.04 s-1). Simultaneous coating was performed using the two discharge heads, the first discharge head 510 and the second discharge head 512 shown in Fig. 4. The simultaneous coating will be described later. The coating weight of the negative electrode active material layer 120 was 11 mg / cm2 , the insulating layer 300 is 2 mg / cm 2 However, as shown in each table, in some examples and comparative examples, samples were prepared in which the basis weight of the insulating layer 300 was changed.

[0129] <Evaluation method> The negative electrode 100 produced by the following method was evaluated. (1) Checking continuity with a tester The test was carried out on the samples of Examples 1 to 11 and Comparative Examples 1 to 14. The results are shown in Tables 1 and 2. (2) Photograph the electrode surface and measure the whiteness The test was carried out on the samples of Example 1 and Comparative Examples 1, 5, and 9. The results are described below.

[0130] (3) Cross-sectional observation A scanning electron microscope (SEM) is used to analyze an SEM image of a cross section of the negative electrode 100. The image analysis involves element mapping using energy dispersive X-ray spectroscopy (EDX). The test was carried out on the samples of Example 1 and Comparative Examples 1, 5, and 9. The results will be described later with reference to FIGS.

[0131] (4) Evaluation of interfacial peel strength between simultaneous coating and sequential coating Using the sample materials of Example 1, a comparison was made between samples produced by simultaneous coating of the present invention and samples produced by sequential coating, and the results are described below.

[0132] In simultaneous coating, the slurries applied in the following steps (A) and (B) are dried simultaneously. Here, the coating steps (A) and (B) are carried out sequentially, and the simultaneous drying of two types of slurries is called simultaneous coating. In the sequential coating, after the following step (A), the slurry applied in step (A) was dried, and then the following step (B) was carried out, and the slurry applied in step (B) was dried. (A) A step of applying a negative electrode active material slurry containing at least a negative electrode active material and a binder. (B) applying an insulating layer slurry containing at least an insulating material and a binder onto the surface of the negative electrode active material layer;

[0133] <Evaluation results> (1) Checking continuity with a tester The tester used was a digital multimeter (CDM-2000) manufactured by Custom Co., Ltd. The resistance range was 30 MΩ. The negative electrode sheet 100A includes copper foil (collector sheet), a negative electrode active material layer 120, and an insulating layer 300. The continuity was confirmed by placing the tester's test lead tips on the front and back of a 10 cm square sample, and if it was at the measurement limit (open range), it was considered "insulated." The continuity was confirmed for 10 samples, and the percentage of insulated samples (number of samples where continuity was not achieved) was calculated. If all 10 samples were insulated, it was 100%.

[0134] As a result of checking the electrical continuity, the insulation rate was 100% in all of Examples 1 to 11. In other words, in all of Examples 1 to 11, good insulation properties were obtained in all of the 10 samples.

[0135] In all of Examples 1 to 11, the binder contained in the insulating layer 300 included at least one selected from styrene butadiene rubber and carboxymethyl cellulose and its salts, and the binder contained in the negative electrode active material layer 120 was at least one selected from polyacrylic acid and its salts. Specifically, in Examples 1 to 11, the binder contained in the insulating layer 300 was a mixture of CMC and SBR, and the binder contained in the negative electrode active material layer 120 was PAA.

[0136] In all of Examples 1 to 11, the D50 particle size, where the cumulative volume in the particle size distribution of the insulating material constituting insulating layer 300 is 50%, was in the range of 0.2 μm to 0.8 μm. Specifically, Example 10 used 0.3 μm (small), Example 11 used 0.6 μm (large), Examples 1 to 8 used 0.7 μm (large), and Example 9 used 0.8 μm (large). No effect of the D50 particle size of the insulating material on the insulation rate was observed.

[0137] In all of Examples 1 to 11, the weight of SBR contained in insulating layer 300 was 3 wt % or more and 6 wt % or less of the total weight of the solid materials constituting insulating layer 300. Specifically, it was 3 wt % in Examples 1 to 3, 6 to 8, and 11, 4 wt % in Examples 4 to 5 and 10, and 6 wt % in Example 9. The total content of CMC and SBR in the binder of insulating layer 300 was 7 wt % in Examples 1 to 2, 6 to 8, and 10, 6 wt % in Examples 3 and 11, 9 wt % in Example 4, 10 wt % in Example 5, and 12 wt % in Example 9. No effect of the total content of CMC and SBR in the binder of insulating layer 300 on the insulation rate was observed.

[0138] In all of Examples 1 to 11, the total weight of the solid materials constituting the negative electrode active material layer 120, of the binders of polyacrylic acid and its salts contained in the negative electrode active material layer 120, was 3 wt % or more and 6 wt % or less. Specifically, the weight of PAA in the binder was 3 wt % in Examples 1 to 6 and 9 to 11, 4 wt % in Example 7, and 6 wt % in Example 8. This was within the range of 3 wt % or more and 6 wt % or less. No effect on the insulation rate was observed due to the content of PAA in the binder of the negative electrode active material layer 120.

[0139] In all of Examples 1 to 11, the insulating material constituting insulating layer 300 contained at least one selected from alumina, silica, acrylic resin, magnesia, calcia, titania, zirconia, boehmite, and magnesium hydroxide. Specifically, Examples 1 to 8 used alumina, Example 9 used acrylic resin, and Examples 10 and 11 used silica.

[0140] Using Example 1 as the standard conditions, the conditions for each Example were changed as follows, as shown in Table 1. In Example 2, the basis weight of the insulating layer 300 in Example 1 was 2.0 mg / cm 2 Larger than 2.6mg / cm 2 The influence of the basis weight of the insulating layer 300 on the insulation rate was not observed.

[0141] In Examples 6 to 8, silica was added to the negative electrode active material, and the content of PAA in the binder was changed. In Example 6, of the total weight of the solid materials constituting the negative electrode active material layer 120, silica was 2.9 wt % (small) and PAA was 3 wt %, in Example 7, silica was 9.6 wt % (medium) and PAA was 4 wt %, and in Example 8, silica was 37.4 wt % (large) and PAA was 6 wt %. The PAA content was 3 wt % or more and 6 wt % or less. Adding silica to the negative electrode active material did not affect the insulation rate.

[0142] (Comparative Example) Table 2 shows the manufacturing conditions and evaluation results of the negative electrodes 100 of Comparative Examples 1 to 14. [Table 2]

[0143] In Comparative Examples 1 to 3, the binder contained in the insulating layer 300 did not contain at least one selected from styrene butadiene rubber and carboxymethyl cellulose and its salts, but PAA was used. The binder contained in the negative electrode active material layer 120 was PAA. In Comparative Example 2, the basis weight of the insulating layer 300 was 2.6 mg / cm 2 was larger than that of Comparative Example 1. In Comparative Example 3, the mixing ratio of PAA as a binding material (binder) contained in insulating layer 300 was larger than that of Comparative Example 1. In Comparative Example 4, silica was added to the graphite of Example 1 as the negative electrode active material, and the weight of PAA as a binder contained in negative electrode active material layer 120 was 4 wt % of the total weight of the solid materials constituting negative electrode active material layer 120, which was larger than that of Comparative Example 1.

[0144] The results of the conductivity check for Comparative Examples 1 to 4 showed an insulation rate of 20%. In other words, in Comparative Examples 1 to 4, two of the ten samples obtained insulation, but eight did not obtain good insulation. In other words, Comparative Examples 1 to 4, in which the binder contained in the insulating layer 300 did not contain at least one selected from styrene-butadiene rubber and carboxymethyl cellulose and its salt, did not provide good insulation. Furthermore, even when the basis weight of the insulating layer 300 was increased (Comparative Example 2), the PAA mixture ratio of the binder contained in the insulating layer 300 was increased (Comparative Example 3), silica was added to the negative electrode active material (Comparative Example 4), or the PAA mixture ratio of the binder of the negative electrode active material layer 120 was increased (Comparative Example 4), the insulation was 20%, and was not affected by these conditions.

[0145] In Comparative Examples 5 to 8, the binder contained in the negative electrode active material layer 120 was not at least one selected from polyacrylic acid and its salts, but CMC and SBR. In Comparative Example 6, the basis weight of the insulating layer 300 was 2.6 mg / cm 2 , which was larger than that of Comparative Example 5. In Comparative Example 7, the mixing ratio of CMC and SBR in the binder of the negative electrode active material layer 120 was larger than that of Comparative Example 5. In Comparative Example 7, the total weight of CMC and SBR in the binder contained in the negative electrode active material layer 120 out of the total weight of the solid materials constituting the negative electrode active material layer 120 was 4 wt %, which was larger than that of Comparative Example 5. In Comparative Example 8, silica was added to the graphite of Comparative Example 5 as the negative electrode active material, and the weight of PAA in the binder contained in the negative electrode active material layer 120 out of the total weight of the solid materials constituting the negative electrode active material layer 120 was 4 wt %, which was larger than that of Comparative Example 5.

[0146] The results of the conduction check for Comparative Examples 5 to 8 showed that the insulation rate was 0%. This indicates that none of the ten samples in Comparative Examples 5 to 7 exhibited good insulation. In other words, Comparative Examples 5 to 8, in which the binder contained in the negative electrode active material layer was not at least one selected from polyacrylic acid and its salts, and the binder contained in the insulating layer 300 did not contain at least one selected from styrene-butadiene rubber and carboxymethyl cellulose and its salts, did not exhibit good insulation. Furthermore, even when the basis weight of the insulating layer 300 was increased (Comparative Example 6), when the mixing ratio of CMC and SBR in the binder of the negative electrode active material layer 120 was increased (Comparative Examples 7 and 8), or when silica was added to the negative electrode active material (Comparative Example 8), the insulation was 0%, and was not affected by these conditions.

[0147] In Comparative Examples 9 to 11, CMC and SBR were used as binders for both the negative electrode active material layer 120 and the insulating layer 300. In Comparative Example 10, the basis weight of the insulating layer 300 was 2.6 mg / cm 2 was larger than that of Comparative Example 9. In Comparative Example 11, the mixing ratio of CMC and SBR in the binder of the negative electrode active material layer 120 was larger than that of Comparative Example 9.

[0148] The results of the conduction check for Comparative Examples 9 to 11 showed that the insulation rate was 0%. In other words, in Comparative Examples 9 to 11, all 10 samples failed to achieve good insulation. In other words, in Comparative Examples 9 to 11, in which the binder contained in the negative electrode active material layer 120 was not at least one selected from polyacrylic acid and its salts, good insulation was not achieved. Furthermore, even when the basis weight of the insulating layer 300 was increased (Comparative Example 10) or the mixture ratio of CMC and SBR in the binder of the negative electrode active material layer 120 was increased (Comparative Example 11), the insulation was 0%, and was not affected by these conditions.

[0149] In Comparative Examples 12 to 14, acrylic resin was used as the insulating material constituting the insulating layer 300. In Comparative Example 12, the binders for both the negative electrode active material layer 120 and the insulating layer 300 were PAA, in Comparative Example 13, the binders for the negative electrode active material layer 120 were CMC and SBR and the binder for the insulating layer 300 was PAA, and in Comparative Example 14, the binders for both the negative electrode active material layer 120 and the insulating layer 300 were CMC and SBR.

[0150] The results of the conduction check for Comparative Example 12 showed an insulation rate of 10%, and 0% for Comparative Examples 13 and 14. That is, even if an acrylic resin was used for insulating layer 300, good insulation properties were not obtained in Comparative Examples 5 to 8, in which the binder contained in the negative electrode active material layer was not at least one selected from polyacrylic acid and its salts, and the binder contained in insulating layer 300 did not include at least one selected from styrene-butadiene rubber and carboxymethyl cellulose and its salts.

[0151] (2) Photograph the electrode surface and measure the whiteness The results obtained for the samples of Example 1 and Comparative Examples 1, 5, and 9 are shown in Table 3 below. [Table 3]

[0152] The whiteness index when only the negative electrode active material layer 120 is present is 11.7, and the whiteness index when only the insulating layer 300 is present is 79.7. That is, in Comparative Example 5, the insulating layer 300 almost completely penetrates the negative electrode active material layer 120, and the whiteness index is almost the same as when only the negative electrode active material layer 120 is present. In Comparative Example 5, the insulation rate is also 0%.

[0153] It can be seen that in Comparative Examples 1 and 9, a certain amount of the insulating layer 300 permeates into the negative electrode active material layer 120, resulting in a lower whiteness value than that obtained when only the insulating layer 300 is used. In Comparative Examples 1 and 9, the insulation rate is also low, ranging from 0 to 20%.

[0154] In Example 1, the whiteness was slightly lower than that in the case of only the insulating layer 300, and the insulation rate was 100%. In other words, it is understood that the insulating layer 300 penetrates into the negative electrode active material layer 120 to a certain extent while maintaining insulation.

[0155] (3) Cross-sectional observation 6 and 7 show cross-sectional results for the samples of Example 1 and Comparative Examples 1, 5, and 9. SEM images and element mapping images using EDX are arranged side by side. The upper image in FIG. 6 shows the results for the sample of Example 1, the lower image in FIG. 6 shows the results for the sample of Comparative Example 9, the upper image in FIG. 7 shows the results for the sample of Comparative Example 1, and the lower image in FIG. 7 shows the results for the sample of Comparative Example 5.

[0156] In the SEM images of each figure, the top layer is the insulating layer 300, the bottom layer is the negative electrode current collector 110, and the center is the negative electrode active material layer 120. Looking at the element mapping image obtained by EDX on the top of FIG. 6 , it can be seen that the second slurry 130A constituting the insulating layer 300 has penetrated the negative electrode active material layer 120 least at the interface between the insulating layer 300 and the negative electrode active material layer 120 of the sample of Example 1. Clearly, a mixed layer 320 of the negative electrode active material layer 120 and the insulating layer 300, which is thinner than the negative electrode active material layer 120, is formed at the interface between the negative electrode active material layer 120 and the insulating layer 300.

[0157] Furthermore, the above Z A / Z B was 6.1%, which was less than 11%. A The insulation rate of the sample of Example 1 was 100%.

[0158] The element mapping image obtained by the EDX method shown at the bottom of FIG. 7 reveals that the second slurry 130A constituting the insulating layer 300 penetrates the negative electrode active material layer 120 most at the interface between the insulating layer 300 and the negative electrode active material layer 120 of the sample of Comparative Example 9. A / Z B The insulation rate of the sample of Comparative Example 9 was 0%.

[0159] 7, the element mapping image obtained by the EDX method shows that the second slurry 130A constituting the insulating layer 300 penetrates less into the negative electrode active material layer 120 at the interface between the insulating layer 300 and the negative electrode active material layer 120 in the sample of Comparative Example 1 (upper side of FIG. 7) than in the sample of Comparative Example 5 (lower side of FIG. 7). A / Z B The insulation ratios of the sample of Comparative Example 1 were 44% and 36%, respectively, both of which were 11% or more. The insulation ratio of the sample of Comparative Example 1 was 20%, which was higher than the insulation ratio of the sample of Comparative Example 5, which was 0%.

[0160] (4) Evaluation of interfacial peel strength between simultaneous coating and sequential coating After tape was applied to the surface of the insulating layer 300 of the sample negative electrode sheet 100A, it was pulled in a direction 180 degrees relative to the sheet surface and then peeled off. In the simultaneously coated sample, only a thin layer of powder from the surface of the insulating layer 300 adhered to the tape. In the sequentially coated sample, the insulating layer 300 peeled off from the interface between the insulating layer 300 and the negative electrode active material layer 120 and was transferred to the tape in stripes. From these results, it can be seen that the interfacial peel strength of the sample produced by simultaneous coating is stronger than that of the sample produced by sequential coating, and peeling hardly occurs.

[0161] Although the present invention has been described above with reference to the embodiments and examples, the present invention is not limited to the above-described embodiments and examples. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

[0162] Below, examples of reference forms are given. 1. On the current collector, A negative electrode for a lithium ion secondary battery, in which a negative electrode active material layer containing at least a negative electrode active material and a binder is formed, an insulating layer including at least an insulating material and a binder on a surface of the negative electrode active material layer; the binder contained in the insulating layer contains at least styrene-butadiene rubber and at least one selected from carboxymethyl cellulose and a salt thereof; The negative electrode for a lithium ion secondary battery, wherein the binder contained in the negative electrode active material layer is at least one selected from polyacrylic acid and salts thereof. 2. A mixed layer of the negative electrode active material layer and the insulating layer, which is thinner than the negative electrode active material layer, is formed at the interface between the negative electrode active material layer and the insulating layer. 1. A negative electrode for a lithium ion secondary battery according to claim 1. 3. When element mapping is performed using an EDX method on a cross-sectional SEM image of the cross section of the negative electrode, the direction from the surface of the negative electrode active material layer that is not in contact with the current collector toward the current collector is defined as the Z direction, and the maximum value in the Z direction at which an element that is not detected in the negative electrode active material but is detected in the insulating material is defined as the Z direction. A and the average thickness of the negative electrode active material layer in the Z direction is Z B When Z A / Z B is 11% or less, 1. A negative electrode for a lithium ion secondary battery according to 1. or 2. 4. The maximum value Z of the thickness in the Z direction A is 35 μm or less, 3. A negative electrode for a lithium ion secondary battery according to claim 3. 5. The D50 particle size, at which the cumulative volume of the particle size distribution of the insulating material is 50%, is 0.2 μm or more and 0.8 μm or less. 5. A negative electrode for a lithium ion secondary battery according to any one of 1. to 4. 6. The weight of styrene butadiene rubber contained in the insulating layer is 3% by weight or more and 6% by weight or less of the total weight of the solid materials constituting the insulating layer. 6. The negative electrode for a lithium ion secondary battery according to any one of 1. to 5. 7. The total weight of the polyacrylic acid and its salts contained in the binder of the polyacrylic acid and its salts contained in the negative electrode active material layer is 3% by weight or more and 6% by weight or less out of the total weight of the solid materials constituting the negative electrode active material layer. 7. The negative electrode for a lithium ion secondary battery according to any one of 1. to 6. 8. The insulating material includes at least one selected from alumina, silica, acrylic resin, magnesia, calcia, titania, zirconia, boehmite, and magnesium hydroxide. 8. A negative electrode for a lithium ion secondary battery according to any one of 1. to 7.

[0163] 9. A lithium ion secondary battery comprising a positive electrode having a positive electrode active material layer formed on a current collector, a negative electrode, and an electrolyte, wherein the negative electrode is the negative electrode according to any one of 1. to 8. Lithium-ion secondary battery. 10. The insulating layer is formed on at least the entire surface of the negative electrode active material layer of the negative electrode facing the region where the active material layer of the positive electrode is formed. 9. The lithium ion secondary battery according to claim 9. 11. A separator different from the insulating layer formed on the negative electrode active material layer of the negative electrode is not disposed between the positive electrode and the negative electrode. 9. The lithium ion secondary battery according to 9. or 10.

[0164] 12. On a sheet-shaped current collector, (A) applying a negative electrode active material slurry containing at least a negative electrode active material and a binder; (B) applying an insulating layer slurry containing at least an insulating material and a binder onto the surface of the negative electrode active material slurry; (C) simultaneously drying the slurries applied in steps (A) and (B); A method for producing a negative electrode for a lithium ion secondary battery, comprising at least the steps of: the binder contained in the insulating layer slurry contains at least styrene-butadiene rubber and at least one selected from carboxymethyl cellulose and a salt thereof; The method for producing a negative electrode for a lithium ion secondary battery, wherein the binder contained in the negative electrode active material slurry is at least one selected from polyacrylic acid and salts thereof. 13. A method for producing a negative electrode sheet for a lithium ion secondary battery by the method according to 12., A method for manufacturing a negative electrode sheet for a lithium ion secondary battery, wherein a negative electrode active material slurry containing at least a negative electrode active material and a binder, and an insulating layer slurry containing at least an insulating material and a binder are continuously applied to a current collector sheet in a direction in which the current collector sheet is continuously transported. 14. Using a discharge head having at least a first discharge port and a second discharge port aligned in the direction in which the current collector sheet is transported, the negative electrode active material slurry is discharged from the first discharge port, and the insulating layer slurry is discharged from the second discharge port. 13. A method for producing a negative electrode sheet for a lithium ion secondary battery according to claim 13. 15. The solid content concentration of the negative electrode active material slurry is 40% or more and 80% or less, and the solid content concentration of the insulating layer slurry is 20% or more and 80% or less. 13. A method for producing a negative electrode sheet for a lithium ion secondary battery according to 14. 16. The viscosity of the negative electrode active material slurry at a shear rate of 2.04 s-1 measured with a Brookfield viscometer at 20°C is 6 Pa·S or more and 10 Pa·S or less, and the viscosity of the insulating layer slurry at a shear rate of 2.04 s-1 measured with a Brookfield viscometer at 20°C is 6 Pa·S or more and 10 Pa·S or less. 15. A method for producing a negative electrode sheet for a lithium ion secondary battery according to claim 15. 17. The D50 particle size, at which the cumulative volume of the particle size distribution of the insulating material contained in the insulating layer slurry is 50%, is 0.2 μm or more and 0.8 μm or less. 17. A method for producing a negative electrode sheet for a lithium ion secondary battery according to any one of 13. to 16. 18. The total weight of the styrene-butadiene rubber contained in the insulating layer is 3% by weight or more and 6% by weight or less of the total weight of the solid materials constituting the insulating layer formed from the insulating layer slurry. 18. A method for producing a negative electrode sheet for a lithium ion secondary battery according to any one of 13. to 17. 19. Of the total weight of solid materials constituting the negative electrode active material layer formed from the negative electrode active material slurry, the total weight of polyacrylic acid and its salts among the binders of polyacrylic acid and its salts contained in the negative electrode active material layer is 3% by weight or more and 6% by weight or less. 19. A method for producing a negative electrode sheet for a lithium ion secondary battery according to any one of 13. to 18. 20. The insulating material includes at least one selected from alumina, silica, acrylic resin, magnesia, calcia, titania, zirconia, boehmite, and magnesium hydroxide. 19. A method for producing a negative electrode sheet for a lithium ion secondary battery according to any one of 13. to 19.

[0165] 21. On the current collector, A negative electrode for a lithium ion secondary battery, in which a negative electrode active material layer containing at least a negative electrode active material and a binder is formed, a high-resistance layer including at least a solid electrolyte and a binder is further provided on a surface of the negative electrode active material layer, the binder contained in the high resistance layer contains at least one selected from styrene butadiene rubber and carboxymethyl cellulose and a salt thereof; The negative electrode for an all-solid-state lithium-ion secondary battery, wherein the binder contained in the negative electrode active material layer is at least one selected from polyacrylic acid and salts thereof. 22. A mixed layer of the negative electrode active material layer and the high resistance layer, which is thinner than the negative electrode active material layer, is formed at the interface between the negative electrode active material layer and the high resistance layer. 21. A negative electrode for an all-solid-state lithium-ion secondary battery according to claim 21. 23. When element mapping is performed on a cross-sectional SEM image of the cross section of the negative electrode using an EDX method, the direction from the surface of the negative electrode active material layer that is not in contact with the current collector toward the current collector is defined as the Z direction, and the maximum value in the Z direction at which an element that is not detected in the negative electrode active material but is detected in the solid electrolyte is defined as Z A and the average thickness of the negative electrode active material layer in the Z direction is Z B When Z A / Z B is 11% or less, 21. or 22. A negative electrode for an all-solid-state lithium-ion secondary battery. 24. Maximum thickness Z in the Z direction A is 35 μm or less, 23. A negative electrode for an all-solid-state lithium-ion secondary battery according to claim 23. 25. The solid electrolyte has a particle size distribution in which the cumulative volume of the particle size is 50%, D50 particle size being 0.2 μm or more and 0.8 μm or less. 25. The negative electrode for an all-solid-state lithium-ion secondary battery according to any one of 21. to 24. 26. The weight of styrene butadiene rubber contained in the high resistance layer is 3% by weight or more and 6% by weight or less of the total weight of the solid materials constituting the high resistance layer. 26. The negative electrode for an all-solid-state lithium-ion secondary battery according to any one of 21. to 25. 27. The total weight of the polyacrylic acid and its salts contained in the binder of the polyacrylic acid and its salts contained in the negative electrode active material layer is 3% by weight or more and 6% by weight or less out of the total weight of the solid materials constituting the negative electrode active material layer. 27. The negative electrode for an all-solid-state lithium-ion secondary battery according to any one of 21. to 26. 28. An all-solid-state lithium-ion secondary battery comprising a positive electrode having a positive electrode active material layer formed on a current collector, a negative electrode, and a solid electrolyte, wherein the negative electrode is the negative electrode according to any one of 21. to 27. All-solid-state lithium-ion secondary battery.

[0166] 29. On a sheet-shaped current collector, (A) applying a negative electrode active material slurry containing at least a negative electrode active material and a binder; (B) applying a high-resistance layer slurry containing at least a solid electrolyte and a binder onto the surface of the negative electrode active material slurry; (C) simultaneously drying the slurries applied in steps (A) and (B); A method for producing a negative electrode for an all-solid-state lithium ion secondary battery, comprising at least the following in this order: the binder contained in the high-resistance layer slurry contains at least one selected from styrene-butadiene rubber and carboxymethyl cellulose and its salt; The method for producing a negative electrode for an all-solid-state lithium-ion secondary battery, wherein the binder contained in the negative electrode active material slurry is at least one selected from polyacrylic acid and salts thereof. 30. A method for producing a negative electrode sheet for an all-solid-state lithium ion secondary battery by the method according to 29., comprising: A method for producing a negative electrode sheet for an all-solid-state lithium-ion secondary battery, wherein a negative electrode active material slurry containing at least a negative electrode active material and a binder, and a high-resistance layer slurry containing at least a solid electrolyte and a binder are continuously applied to a current collector sheet in a direction in which the current collector sheet is continuously transported. [Explanation of symbols]

[0167] 10 Lithium-ion secondary battery 12 Laminate 150 1st Lead 250 2nd Lead 400 exterior materials 100 negative electrode 100A negative electrode sheet 110 Negative electrode current collector 110A negative electrode current collector sheet 112 Page 1 114 Side 2 120 Negative electrode active material layer 122 sides 200 positive electrode 210 Positive electrode current collector 212 Page 3 214 Page 4 220 Cathode active material layer 300 insulating layer 312 Page 5 314 Page 6 320 mixed layer 120A First Slurry 130A Second Slurry 500 devices 510 First ejection head 510a outlet 512 Second ejection head 512a Discharge port 522 First Tank 524 First Pump 526 First Valve 532 Second Tank 534 Second Pump 536 Second Valve 542 First conveyor roller 544 Second conveyor roller 546 Third conveyor roller 550 Dryer

Claims

1. On one side of the current collector, A negative electrode for a lithium ion secondary battery, in which a negative electrode active material layer containing at least a negative electrode active material and a binder is formed, the negative electrode active material layer further has an insulating layer containing at least an insulating material and a binder on a first surface thereof, the first surface being the surface opposite to the current collector; the binder contained in the insulating layer contains at least styrene-butadiene rubber and at least one selected from carboxymethyl cellulose and a salt thereof; the binder contained in the negative electrode active material layer is at least one selected from polyacrylic acid and salts thereof, When element mapping is performed on a cross-sectional SEM image of the cross section of the negative electrode using an EDX method, the direction from the first surface of the negative electrode active material layer toward the one surface of the current collector in the negative electrode active material layer is defined as a Z direction, and the maximum value in the Z direction in which an element that is not detected in the negative electrode active material but is detected in the insulating material is defined as Z Ａ and the average thickness in the Z direction of the negative electrode active material layer is Z Ｂ When this is done, Z Ａ / Z Ｂ A negative electrode for a lithium ion secondary battery, wherein the content of the negative electrode is 11% or less.

2. The maximum value Z of the thickness in the Z direction Ａ is 35 μm or less, The negative electrode for a lithium ion secondary battery according to claim 1 .

3. The insulating material has a particle size distribution in which the cumulative volume of the particle size is 50% (D50 particle size) of 0.2 μm or more and 0.8 μm or less. The negative electrode for a lithium ion secondary battery according to claim 1 or 2.

4. the weight of the styrene-butadiene rubber contained in the insulating layer is 3% by weight or more and 6% by weight or less of the total weight of the solid materials constituting the insulating layer; The negative electrode for a lithium ion secondary battery according to claim 1 .

5. the total weight of the polyacrylic acid and its salt contained in the binder of the polyacrylic acid and its salt contained in the negative electrode active material layer is 3% by weight or more and 6% by weight or less of the total weight of the solid materials constituting the negative electrode active material layer; The negative electrode for a lithium ion secondary battery according to claim 1 .

6. the insulating material includes at least one selected from alumina, silica, acrylic resin, magnesia, calcia, titania, zirconia, boehmite, and magnesium hydroxide; The negative electrode for a lithium ion secondary battery according to claim 1 .

7. A lithium ion secondary battery comprising a positive electrode having a positive electrode active material layer formed on a current collector, a negative electrode, and an electrolyte, wherein the negative electrode is the negative electrode according to any one of claims 1 to 6. Lithium-ion secondary battery.

8. the insulating layer is formed on the entire first surface; The lithium ion secondary battery according to claim 7.

9. a separator different from the insulating layer formed on the negative electrode active material layer of the negative electrode is not disposed between the positive electrode and the negative electrode; The lithium ion secondary battery according to claim 7 or 8.

10. On one side of the current collector, A negative electrode for a lithium ion secondary battery, in which a negative electrode active material layer containing at least a negative electrode active material and a binder is formed, the negative electrode active material layer further has a high-resistance layer containing at least a solid electrolyte and a binder on a first surface thereof, the first surface being the surface opposite to the current collector; the binder contained in the high resistance layer contains at least one selected from styrene-butadiene rubber and carboxymethyl cellulose and a salt thereof; the binder contained in the negative electrode active material layer is at least one selected from polyacrylic acid and salts thereof, When element mapping is performed on a cross-sectional SEM image of the cross section of the negative electrode using an EDX method, the direction from the first surface of the negative electrode active material layer toward the one surface of the current collector in the negative electrode active material layer is defined as the Z direction, and the maximum value in the Z direction in which an element that is not detected in the negative electrode active material but is detected in the solid electrolyte is defined as Z Ａ and the average thickness in the Z direction of the negative electrode active material layer is Z Ｂ When this is done, Z Ａ / Z Ｂ A negative electrode for an all-solid-state lithium-ion secondary battery, wherein the content of the negative electrode is 11% or less.

11. The maximum value Z of the thickness in the Z direction Ａ is 35 μm or less, The negative electrode for an all-solid-state lithium ion secondary battery according to claim 10.

12. a D50 particle size at which the cumulative volume of the particle size distribution of the solid electrolyte is 50% is 0.2 μm or more and 0.8 μm or less; The negative electrode for an all-solid-state lithium ion secondary battery according to claim 10 or 11.

13. the weight of the styrene-butadiene rubber contained in the high-resistance layer is 3% by weight or more and 6% by weight or less of the total weight of the solid material constituting the high-resistance layer; The negative electrode for an all-solid-state lithium ion secondary battery according to any one of claims 10 to 12.

14. the total weight of the polyacrylic acid and its salt contained in the binder of the polyacrylic acid and its salt contained in the negative electrode active material layer is 3% by weight or more and 6% by weight or less of the total weight of the solid materials constituting the negative electrode active material layer; The negative electrode for an all-solid-state lithium ion secondary battery according to any one of claims 10 to 13.

15. An all-solid-state lithium ion secondary battery comprising a positive electrode having a positive electrode active material layer formed on a current collector, a negative electrode, and a solid electrolyte, wherein the negative electrode is the negative electrode according to any one of claims 10 to 14. All-solid-state lithium-ion secondary battery.

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