Negative electrode for non-aqueous electrolyte secondary batteries

Abstract

It inhibits delamination in multilayer structures. [Solution] The negative electrode for a non-aqueous electrolyte secondary battery comprises a current collector, a first active material layer, and a second active material layer in that order. The negative electrode for a non-aqueous electrolyte secondary battery further comprises carbon nanotubes. The carbon nanotubes are unevenly distributed at the interface between the first active material layer and the second active material layer.

Description

Technical Field

[0001] The present disclosure relates to a negative electrode for non-aqueous electrolyte secondary batteries.

Background Art

[0002] U.S. Patent Application Publication No. 2021 / 0391570 discloses a negative electrode active material layer that has a two-layer structure and in which the respective layers have compositions different from each other.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] For example, by laminating active material layers having compositions different from each other, various performance improvements are expected. However, on the other hand, due to the different compositions of the respective layers, a mismatch in expansion and contraction between the layers may occur. The mismatch in expansion and contraction may cause delamination between the layers.

[0005] An object of the present disclosure is to inhibit delamination in a multilayer structure.

Means for Solving the Problems

[0006] Hereinafter, the technical configuration and operational effects of the present disclosure will be described. However, the operational mechanism includes estimations. The operational mechanism does not limit the technical scope of the present disclosure.

[0007] 1. A negative electrode for non-aqueous electrolyte secondary batteries according to one aspect of the present disclosure includes a current collector, a first active material layer, and a second active material layer in this order. The negative electrode for non-aqueous electrolyte secondary batteries further includes carbon nanotubes. The carbon nanotubes are unevenly distributed at the interface between the first active material layer and the second active material layer.

[0008] Hereinafter, "negative electrode for non-aqueous electrolyte secondary battery" may be abbreviated as "negative electrode". Figure 1 is a conceptual cross-sectional view showing the first stacked structure in this embodiment. The negative electrode 20 includes a current collector 21, a first active material layer 22a, and a second active material layer 22b in that order. To inhibit delamination, for example, a binder layer 22d may be introduced between the first active material layer 22a and the second active material layer 22b. However, the binder may inhibit ion diffusion and electron conduction. The introduction of the binder layer 22d may increase resistance.

[0009] Figure 2 is a conceptual cross-sectional view showing the second layered structure in this embodiment. In the second layered structure, carbon nanotubes (CNTs) are unevenly distributed between the first active material layer 22a and the second active material layer 22b. The CNTs 1 are fibrous. The CNTs 1 can entangle with both the particles contained in the first active material layer 22a and the particles contained in the second active material layer 22b. Therefore, the CNTs 1 are expected to inhibit delamination. Furthermore, the CNTs 1 can form long-distance electron conduction paths. By forming electron conduction paths connecting the first active material layer 22a and the second active material layer 22b, a reduction in resistance is also expected.

[0010] 2. The negative electrode for a non-aqueous electrolyte secondary battery described in item "1" above may include, for example, the following configuration: The first active material layer includes a first negative electrode active material. The second active material layer includes a second negative electrode active material. The second negative electrode active material has a different composition from the first negative electrode active material.

[0011] For example, if the composition of the negative electrode active material differs between the first active material layer and the second active material layer, a mismatch may occur in the amount of expansion and contraction, expansion and contraction timing, etc., during charging and discharging. For example, the content of Si-based active material, etc., may differ between the first active material layer and the second active material layer.

[0012] 3. The negative electrode for a non-aqueous electrolyte secondary battery described in item "1" or "2" above may include, for example, the following configuration: A first active material layer comprises a first negative electrode active material. A second active material layer comprises a second negative electrode active material. The second negative electrode active material has a different orientation angle from the first negative electrode active material. The orientation angle is the acute angle formed between the major axis diameter of the particles and the surface of the current collector.

[0013] The orientation angle is an indicator of orientation. The closer the orientation angle is to 90°, the more the particles are considered to be oriented in the thickness direction of the active material layer. For example, if the orientation of the negative electrode active material differs between the first and second active material layers, a mismatch may occur in the amount and direction of expansion and contraction during charging and discharging. For example, the orientation of natural graphite, artificial graphite, etc., may differ between the first and second active material layers.

[0014] 4. The negative electrode for a non-aqueous electrolyte secondary battery described in any one of the above items "1" to "3" may include, for example, the following configuration: The second active material layer has a different porosity from the first active material layer.

[0015] For example, a difference in porosity between the first active material layer and the second active material layer may lead to a mismatch in expansion and contraction during charging and discharging. For instance, the second active material layer (upper layer) may have a relatively higher porosity than the first active material layer (lower layer). A relatively higher porosity in the upper layer is expected to promote the diffusion of the electrolyte and reduce resistance.

[0016] 5. A negative electrode for a non-aqueous electrolyte secondary battery in one aspect of the present disclosure comprises, in this order, a current collector, a first active material layer, and a second active material layer. The negative electrode for a non-aqueous electrolyte secondary battery further comprises carbon nanotubes and a binder. The carbon nanotubes are unevenly distributed at the interface between the first active material layer and the second active material layer. The second active material layer has a different porosity than the first active material layer. The first active material layer contains a first negative electrode active material. The second active material layer contains a second negative electrode active material. The second negative electrode active material has a different composition from the first negative electrode active material. The second negative electrode active material has a different orientation angle from the first negative electrode active material. The orientation angle is the acute angle between the long axis diameter of the particles and the surface of the current collector. The binder comprises styrene-butadiene rubber, carboxymethylcellulose, and an acrylic polymer. The styrene-butadiene rubber is unevenly distributed in the first active material layer. Carboxymethylcellulose is unevenly distributed in the second active material layer. Acrylic polymers are unevenly distributed at the interface between the first and second active material layers.

[0017] Figure 3 is a conceptual cross-sectional view showing the third layered structure in this embodiment. For example, an acrylic polymer (binder) may be introduced at the interface between the first active material layer 22a and the second active material layer 22b, in addition to CNTs. The CNTs and acrylic polymer may form an intervening layer 22c. The acrylic polymer may have higher ion permeability compared to styrene-butadiene rubber (SBR) and carboxymethylcellulose (CMC). The synergistic effect of the acrylic polymer and CNTs is expected to improve peelability.

[0018] One embodiment of the present disclosure (which may be abbreviated as "this embodiment") is described below. However, this embodiment does not limit the technical scope of the present disclosure. This embodiment is illustrative in all respects. This embodiment is non-restrictive. The technical scope of the present disclosure includes all modifications within the meaning and scope equivalent to the claims. For example, it is intended from the outset that any configuration may be extracted from this embodiment and combined in any way. [Brief explanation of the drawing]

[0019] [Figure 1] This is a conceptual cross-sectional view showing the first laminated structure in the present embodiment. [Figure 2] This is a conceptual cross-sectional view showing the second laminated structure in the present embodiment. [Figure 3] This is a conceptual cross-sectional view showing the third laminated structure in the present embodiment. [Figure 4] This is a conceptual cross-sectional view for explaining the orientation angle in the present embodiment. [Figure 5] This is a conceptual diagram showing an example of the non-aqueous electrolyte secondary battery in the present embodiment. [Mode for Carrying Out the Invention]

[0020] Terms and Phrases The terms "comprising", "including", "having" and their variations are open-ended expressions. A configuration expressed in an open-ended manner may or may not further include additional elements in addition to the essential elements. The recitation "consisting of" is a closed expression. However, even a configuration expressed in a closed manner may usually include accompanying impurities or additional elements that are irrelevant to the target technology. The recitation "consisting essentially of" is a semi-closed expression. In a configuration expressed in a semi-closed manner, addition of elements that do not substantially affect the basic and novel characteristics of the target technology is permitted.

[0021] Geometric terms should not be interpreted in a strict sense. Examples of geometric terms include "parallel", "perpendicular", "orthogonal" and the like. For example, directions, angles, distances and the like may be relatively displaced within a range where substantially the same or similar functions can be obtained. Geometric terms may include, for example, tolerances, errors and the like in design, work, manufacturing and the like. The dimensional relationships in each drawing may not match the actual dimensional relationships. The dimensional relationships in each drawing may be modified to facilitate the reader's understanding. For example, length, width, thickness and the like may be modified. Some configurations may be omitted.

[0022] Unless otherwise specified, the singular form is not limited to a single element. The singular form can also include multiple elements.

[0023] "Artificial graphite" refers to graphite synthesized by artificial heat treatment. Artificial graphite is also called synthetic graphite (SD). "Natural graphite" refers to graphite produced in nature. Natural graphite includes flake graphite. Flake graphite may be rolled up so that the edges of the particles are folded. "Si-based active material" includes Si (or Si compounds, Si alloys, etc.) that can be alloyed with Li. Si-based active material may include, for example, at least one selected from the group consisting of pure Si, Si-based alloys, SiO, and Si-C. "Si-C" refers to composite particles containing at least one of Si and SiO, and carbon. For example, Si may be supported on a carbon material.

[0024] The "aspect ratio" indicates the ratio of the longer side to the shorter side of the MBR. The arithmetic mean of the aspect ratios of 100 randomly selected particles is used.

[0025] Figure 4 is a conceptual cross-sectional view illustrating the orientation angle in this embodiment. The "orientation angle" is the acute angle "θ" between the major axis diameter "L" of a particle (e.g., natural graphite) and the surface of the current collector 21 in a cross-sectional SEM (Scanning Electron Microscope) image of the negative electrode 20. The orientation angle can take values ​​from 0° to 90°. The major axis diameter indicates the maximum Ferret diameter of the particle. The arithmetic mean of the orientation angles of 100 randomly selected particles is used.

[0026] "Basis Weight" indicates the mass per unit area.

[0027] The "porosity" is determined by image analysis. Cross-sectional SEM images of each layer are binarized to distinguish between voids and solids. The porosity is calculated by dividing the total area of ​​the voids (total pixels) by the total area of ​​the layer.

[0028] The term "active material layer" is a collective term for the first active material layer and the second active material layer.

[0029] Nonaqueous electrolyte secondary battery Figure 5 is a conceptual diagram showing an example of a non-aqueous electrolyte secondary battery in this embodiment. The non-aqueous electrolyte secondary battery 100 may include, for example, a power generation element 50 and a case 60. The case 60 houses the power generation element 50. The case 60 may be, for example, a metal container, a pouch made of aluminum laminate film, etc. The power generation element 50 may include, for example, a positive electrode 10, a negative electrode 20, a separator 30, and a non-aqueous electrolyte (not shown). The power generation element 50 may be, for example, a wound type or a stacked type. The power generation element 50 may have a monopolar structure or a bipolar structure. The separator 30 can electrically separate the negative electrode 20 from the positive electrode 10. The separator 30 may include, for example, a porous membrane made of resin. The non-aqueous electrolyte is a Li ion conductor. The non-aqueous electrolyte may include, for example, a Li salt and an organic solvent. The non-aqueous electrolyte may, for example, be impregnated into the separator 30. The non-aqueous electrolyte may include, for example, a polymer electrolyte, a gel electrolyte, or a solid electrolyte. The solid electrolyte may include, for example, a sulfide solid electrolyte, an oxide solid electrolyte, a halide solid electrolyte, etc. The positive electrode 10 contains a positive electrode active material. The positive electrode active material may include, for example, a lithium transition metal composite oxide (Li[NiCoMn]O2), a lithium phosphate compound (Li[FeMn]PO4), etc. Note that the notation [NiCoMn], [FeMn], etc. indicates that the sum of the composition ratios of the components in [] is "1". As long as the sum is 1, the composition ratio of each component is arbitrary. For example, the composition ratio of some components may be zero.

[0030] negative electrode The negative electrode 20 may be, for example, in the form of a sheet. The negative electrode 20 has a multilayer structure. In the thickness direction, the negative electrode 20 includes a current collector 21, a first active material layer 22a, and a second active material layer 22b in this order. The active material layer may be arranged on a part of the surface of the current collector 21 or on the entire surface. The active material layer may be arranged on only one side of the current collector 21 or on both sides of the current collector 21. The current collector 21 may include, for example, a metal foil (Cu foil, Ni foil, etc.), a conductive resin layer, etc. The current collector 21 may have a thickness of, for example, 1 μm to 100 μm. In addition to the first active material layer 22a and the second active material layer 22b, the negative electrode 20 may further include a third active material layer, a fourth active material layer (not shown), etc.

[0031] CNTs are unevenly distributed at the interface between the first active material layer 22a and the second active material layer 22b. As long as they are unevenly distributed at this interface, CNTs may also be present in, for example, the first active material layer 22a and the second active material layer 22b. That is, in the thickness direction (Z-axis direction), the abundance of CNTs is highest at the interface between the first active material layer 22a and the second active material layer 22b. CNTs may extend from the interior of the first active material layer 22a to the interior of the second active material layer 22b. CNTs may be, for example, single-walled CNTs or multi-walled CNTs. The average fiber diameter of the CNTs may be, for example, 1 nm or more, 10 nm or more, 50 nm or more, 100 nm or more, 200 nm or more, or 300 nm or more. The average fiber diameter of the CNTs may be, for example, less than 1000 nm, 500 nm or less, 300 nm or less, 200 nm or less, 100 nm or less, or 50 nm or less. The average fiber length of CNTs may be, for example, 1 μm or more, 5 μm or more, or 10 μm or more. The average fiber length of CNTs may be, for example, 100 μm or less, 50 μm or less, 30 μm or less, or 20 μm or less. The "average fiber diameter" and "average fiber length" are measured by microscopy. The average fiber diameter is the arithmetic mean of the fiber diameters of 10 randomly selected CNTs. The average fiber length is the arithmetic mean of the fiber lengths of 10 randomly selected CNTs.

[0032] The first active material layer 22a and the second active material layer 22b may be, for example, coating layers. The coating layer refers to a layer formed by the application of paint. Each paint may be applied substantially simultaneously or sequentially. For example, CNTs may be sprinkled on the surface of the first active material layer 22a after drying. For example, CNTs may be sprinkled on the surface of the first active material layer 22a (paint) before drying. For example, a paint containing CNTs may be applied to the surface of the first active material layer 22a after drying. For example, a paint containing CNTs may be applied to the surface of the first active material layer 22a (paint) before drying.

[0033] The first active material layer 22a is a lower layer. The first active material layer 22a may be formed directly on the surface of the current collector 21. The first active material layer 22a contains a first negative electrode active material. The first active material layer 22a may further contain a conductive material, a binder, etc. For example, the first active material layer 22a may contain, by mass fraction, 0% to 10% of a conductive material, 0% to 10% of a binder, and the remainder being the first negative electrode active material. For example, the first active material layer 22a may contain, by mass fraction, 0.5% to 1.5% of a conductive material, 0.5% to 3% of a binder, and the remainder being the first negative electrode active material. The first negative electrode active material may contain at least one selected from the group consisting of natural graphite, artificial graphite, and Si-based active materials.

[0034] The second active material layer 22b is the upper layer. The second active material layer 22b may form the outermost surface of the negative electrode 20. The second active material layer 22b contains the second negative electrode active material. The second active material layer 22b may further contain a conductive material, a binder, etc. For example, the second active material layer 22b may contain, by mass fraction, 0% to 10% of a conductive material, 0% to 10% of a binder, and the remainder being the second negative electrode active material. For example, the second active material layer 22b may contain, by mass fraction, 0.5% to 1.5% of a conductive material, 0.5% to 3% of a binder, and the remainder being the second negative electrode active material.

[0035] In the first active material layer 22a and the second active material layer 22b, the conductive material may include at least one selected from the group consisting of carbon black, CNTs, vapor-grown carbon fibers, and graphene flakes. By including CNTs in the active material layer, the CNTs within the active material layer and the CNTs arranged between the layers become entangled, which is expected to improve, for example, peel strength and electronic conductivity.

[0036] In the first active material layer 22a and the second active material layer 22b, the binder may contain at least one selected from the group consisting of SBR, CMC, polyvinylidene fluoride, polytetrafluoroethylene, and acrylic polymers. The binder may be in the form of a film or fibers.

[0037] At least one of the composition and structure differs between the first active material layer 22a and the second active material layer 22b. For example, the second anode active material may have a different composition from the first anode active material. For example, the Si-based active material content may differ between the second anode active material and the first anode active material. The ratio "C2 / C1" of the Si-based active material content "C2" in the second anode active material to the Si-based active material content "C1" in the first anode active material may be, for example, 0.1 or more, 0.5 or more, or 2 or more. "C2 / C1" may be, for example, 10 or less, 2 or less, or 0.5 or less.

[0038] For example, the mixing ratio of natural graphite and artificial graphite may differ between the first negative electrode active material and the second negative electrode active material. In the first active material layer 22a, for example, a relationship such as "natural graphite / artificial graphite = 10 / 0 to 6 / 4" in mass ratio may be satisfied. In the second active material layer 22b, for example, a relationship such as "natural graphite / artificial graphite = 0 / 10 to 4 / 6" in mass ratio may be satisfied.

[0039] For example, the second negative electrode active material may have a different orientation angle than the first negative electrode active material. For example, the orientation angle can be adjusted by applying a magnetic field to the coating layer before drying. For example, the orientation angle of the first negative electrode active material may be larger than that of the second negative electrode active material. For example, the orientation angle of the second negative electrode active material may be larger than that of the first negative electrode active material. The orientation angles of the first negative electrode active material and the orientation angles of the second negative electrode active material may be independently, for example, 1° or more, 5° or more, 15° or more, 30° or more, 45° or more, 60° or more, or 75° or more. The orientation angles of the first negative electrode active material and the orientation angles of the second negative electrode active material may be independently, for example, 90° or less, 75° or less, 60° or less, 45° or less, 30° or less, or 15° or less.

[0040] For example, the particle shapes of the first negative electrode active material and the second negative electrode active material may differ. For example, the first negative electrode active material may be spherical or ellipsoidal, and the second negative electrode active material may be flaky. For example, the second negative electrode active material may be spherical or ellipsoidal, and the first negative electrode active material may be flaky. For example, the second negative electrode active material may have a different aspect ratio from the first negative electrode active material. For example, the aspect ratio of the first negative electrode active material may be larger than that of the second negative electrode active material. For example, the aspect ratio of the second negative electrode active material may be larger than that of the first negative electrode active material. The aspect ratio of the first negative electrode active material and the aspect ratio of the second negative electrode active material may be independently, for example, 1 or more, 1.2 or more, 1.5 or more, 2 or more, 3 or more, 4 or more, or 5 or more. The aspect ratio of the first negative electrode active material and the aspect ratio of the second negative electrode active material may be independently, for example, 6 or less, 5 or less, 4 or less, 3 or less, 2 or less, 1.5 or less, or 1.2 or less.

[0041] For example, the second active material layer 22b may have a different porosity than the first active material layer 22a. For example, the porosity of the first active material layer 22a may be greater than that of the second active material layer 22b. For example, the porosity of the second active material layer 22b may be greater than that of the first active material layer 22a. The porosity of the first active material layer 22a and the porosity of the second active material layer 22b may be independently, for example, 1% or more, 5% or more, 10% or more, 20% or more, 30% or more, or 40% or more. The porosity of the first active material layer 22a and the porosity of the second active material layer 22b may be independently, for example, 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, or 5% or less.

[0042] For example, the binder composition may differ between the first active material layer 22a and the second active material layer 22b. For example, SBR may be unevenly distributed in the first active material layer 22a. For example, CMC may be unevenly distributed in the second active material layer 22b. For example, in the first active material layer 22a, relationships such as "SBR / CMC = 1.1 / 0.9 to 1.9 / 0.1", "SBR / CMC = 1.2 / 0.8 to 1.8 / 0.2", and "SBR / CMC = 1.5 / 0.5 to 1.8 / 0.2" may be satisfied in terms of mass ratio. For example, in the second active material layer 22b, relationships such as "SBR / CMC = 0.9 / 1.1 to 0.1 / 1.9", "SBR / CMC = 0.8 / 1.2 to 0.2 / 1.8", and "SBR / CMC = 0.5 / 1.5 to 0.2 / 1.8" may be satisfied in terms of mass ratio.

[0043] An intervening layer 22c may be formed between the first active material layer 22a and the second active material layer 22b. The intervening layer 22c contains CNTs and an acrylic polymer. For example, the intervening layer 22c may be formed by applying a coating containing CNTs and an acrylic polymer to the surface of the first active material layer 22a. That is, the acrylic polymer may be unevenly distributed at the interface between the first active material layer 22a and the second active material layer 22b.

[0044] The intervening layer 22c may be a layer that is substantially free of negative electrode active material. The intervening layer 22c may, for example, contain, by mass fraction, 1 to 99% of an acrylic polymer and the remainder being CNTs. The mass fraction of the acrylic polymer may be, for example, 5% or more, 10% or more, 20% or more, 30% or more, 40% or more, 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, or 95% or more. The mass fraction of the acrylic polymer may be, for example, 95% or less, 90% or less, 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, or 5% or less.

[0045] The thickness "T3" of the interlayer 22c may be smaller than, for example, the thickness "T1" of the first active material layer 22a and the thickness "T2" of the second active material layer 22b. The thickness "T3" of the interlayer 22c may be, for example, 10 μm or less, 5 μm or less, or 3 μm or less. The thickness "T3" of the interlayer 22c may be, for example, 0.5 μm or more, 1 μm or more, or 3 μm or more. The basis weight "W3" of the interlayer 22c may be smaller than, for example, the basis weight "W1" of the first active material layer 22a and the basis weight "W2" of the second active material layer 22b. The basis weight "W3" of the interlayer 22c may be, for example, 5 mg / cm 2 Below, 3mg / cm 2 The following, or 1 mg / cm³ 2 The following may also apply: The basis weight "W3" of the interlayer 22c is, for example, 0.1 mg / cm³. 2 Above, or 0.5 mg / cm³ 2 That's fine too.

[0046] Acrylic polymers may be homopolymers or copolymers. At least a portion of the constituent units of an acrylic polymer are derived from acrylic monomers. Acrylic monomers may, for example, have at least one of an acrylic group and a methacrylic group. Acrylic monomers may include, for example, at least one selected from the group consisting of acrylic acid, acrylic acid esters, methacrylic acid, and methacrylic acid esters. Acrylic monomers may also include, for example, at least one selected from the group consisting of ethyl acrylate, methyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, isononyl acrylate, hydroxyethyl acrylate, methyl methacrylate, glycidyl methacrylate, acrylonitrile, acrylamide, and acrylamide. Some of the constituent units of an acrylic polymer may be derived from monomers other than acrylic monomers. For example, some of the constituent units may be derived from styrene. [Explanation of Symbols]

[0047] 1 CNT, 10 positive electrode, 20 negative electrode, 21 current collector, 22a first active material layer, 22b second active material layer, 22c interlayer layer, 22d binder layer, 30 separator, 50 power generation element, 60 case, 100 non-aqueous electrolyte secondary battery.

Claims

1. The current collector, the first active material layer, and the second active material layer are included in this order. It further contains carbon nanotubes, and Carbon nanotubes are unevenly distributed at the interface between the first active material layer and the second active material layer. Negative electrode for non-aqueous electrolyte secondary batteries.

2. The first active material layer contains the first negative electrode active material. The second active material layer contains a second negative electrode active material, The second negative electrode active material has a different composition from the first negative electrode active material. The negative electrode for a non-aqueous electrolyte secondary battery according to claim 1.

3. The first active material layer contains the first negative electrode active material. The aforementioned second active material layer contains a second negative electrode active material. The second negative electrode active material has a different orientation angle from the first negative electrode active material, and The orientation angle indicates the acute angle formed between the major axis diameter of the particle and the surface of the current collector. The negative electrode for a non-aqueous electrolyte secondary battery according to claim 1.

4. The second active material layer has a different porosity than the first active material layer. A negative electrode for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 3.

5. The current collector, the first active material layer, and the second active material layer are included in this order. Further containing carbon nanotubes and a binder, Carbon nanotubes are unevenly distributed at the interface between the first active material layer and the second active material layer. The second active material layer has a different porosity than the first active material layer. The first active material layer contains the first negative electrode active material. The aforementioned second active material layer contains a second negative electrode active material. The second negative electrode active material has a different composition from the first negative electrode active material. The second negative electrode active material has a different orientation angle from the first negative electrode active material. The orientation angle indicates the acute angle formed between the major axis diameter of the particle and the surface of the current collector. The binder comprises styrene-butadiene rubber, carboxymethylcellulose, and an acrylic polymer. Styrene-butadiene rubber is unevenly distributed in the first active material layer. Carboxymethylcellulose is unevenly distributed in the second active material layer, and The acrylic polymer is unevenly distributed at the interface between the first active material layer and the second active material layer. Negative electrode for non-aqueous electrolyte secondary batteries.

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