Negative electrode for nonaqueous electrolyte secondary batteries and nonaqueous electrolyte secondary battery

Abstract

A negative electrode for a nonaqueous electrolyte secondary battery according to an embodiment of the present disclosure includes a negative electrode mixture layer. The negative electrode mixture layer contains a negative electrode active material and a binder component. The binder component contains a binder compound and a chelating agent. Suppose the porosity of the negative electrode mixture layer is ε%, the relationship of 5 < ε ≤ 30 is established.

Description

Negative electrode for non-aqueous electrolyte secondary battery and non-aqueous electrolyte secondary battery

[0001] The present invention relates to a negative electrode for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery.

[0002] Non-aqueous electrolyte secondary batteries are used in various applications as high-capacity secondary batteries. A non-aqueous electrolyte secondary battery includes a positive electrode, a negative electrode, and a non-aqueous electrolyte. Regarding the negative electrode of such a non-aqueous electrolyte secondary battery, various proposals have been made in the past.

[0003] In Patent Document 1, a negative electrode for a non-aqueous electrolyte secondary battery, the negative electrode includes a negative electrode active material, a binder, and a conductive assistant, and the negative electrode active material is SiO ｘ (where x is a number satisfying 0.5 ≦ x ≦ 1.6), a silicon-based active material (A) containing the same, a carbon-based active material (B) composed of secondary particles formed by aggregation of primary particles, and a carbon-based active material (C) composed of primary particles different from the carbon-based active material (B), the average particle diameter of the metal silicon particles contained in the silicon-based active material (A) is 0.5 nm or more and 10 nm, the conductive assistant has a linear shape, the diameter of the wire is 1 nm or more and 4 nm or less, and the length of the wire is 2 μm or more and 15 μm or less. A negative electrode for a non-aqueous electrolyte secondary battery has been proposed.

[0004] Patent Document 1 discloses that by using the negative electrode for a non-aqueous electrolyte secondary battery as described above, the life (cycle characteristics) of the non-aqueous electrolyte secondary battery, in other words, the capacity retention rate of the non-aqueous electrolyte secondary battery can be improved.

[0005] Japanese Unexamined Patent Application Publication No. 2024-141386

[0006] A negative electrode for a non-aqueous electrolyte secondary battery usually includes a negative electrode current collector and a negative electrode mixture layer disposed on the negative electrode current collector, and the negative electrode mixture layer includes, for example, a negative electrode active material, a binder, and a conductive assistant. In the negative electrode mixture layer, for example, the negative electrode active materials are connected through the conductive assistant to form a conductive path. In such a negative electrode mixture layer, the negative electrode active material expands during charging and contracts during discharging. Therefore, in a non-aqueous electrolyte secondary battery, along with the expansion and contraction of this negative electrode active material, the negative electrode mixture layer also repeats expansion and contraction during charge and discharge.

[0007] Here, the larger the porosity of the negative electrode mixture layer, the greater the degree of expansion and contraction of the negative electrode mixture layer. When the degree of expansion and contraction of the negative electrode mixture layer increases, the effect on the conductive paths formed within the negative electrode mixture layer also increases. Furthermore, if the conductive paths within the negative electrode mixture layer become disconnected due to the expansion and contraction of the negative electrode mixture layer, the capacity retention rate of the non-aqueous electrolyte secondary battery will decrease.

[0008] However, no prior art document, including Patent Document 1, has yet adequately addressed the issue of suppressing the decrease in capacity retention rate of non-aqueous electrolyte secondary batteries due to an increase in the porosity of the negative electrode mixture layer.

[0009] Therefore, the object of this disclosure is to provide a negative electrode for a non-aqueous electrolyte secondary battery that can suppress the decrease in the capacity retention rate of the non-aqueous electrolyte secondary battery, and a non-aqueous electrolyte secondary battery equipped with such a negative electrode for a non-aqueous electrolyte secondary battery.

[0010] One aspect of the present invention relates to a negative electrode for a non-aqueous electrolyte secondary battery, comprising a negative electrode mixture layer, wherein the negative electrode mixture layer comprises a negative electrode active material and a binder component, the binder component comprises a binder compound and a chelating agent, and when the porosity of the negative electrode mixture layer is ε%, the relationship ε < ε ≤ 30 is satisfied.

[0011] Another aspect of this disclosure relates to a non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte, wherein the negative electrode is the negative electrode for the non-aqueous electrolyte secondary battery described above.

[0012] According to this disclosure, it is possible to provide a negative electrode for a non-aqueous electrolyte secondary battery that can suppress the decrease in the capacity retention rate of the non-aqueous electrolyte secondary battery. Furthermore, it is possible to provide a non-aqueous electrolyte secondary battery equipped with such a negative electrode for a non-aqueous electrolyte secondary battery.

[0013] This is a schematic cross-sectional view showing a non-aqueous electrolyte secondary battery according to one embodiment of the present disclosure.

[0014] The embodiments of this disclosure will be described below with examples, but this disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be given as examples, but other numerical values, materials, etc. may be applied as long as the effects of this disclosure are obtained. Notwithstanding, known components may be applied to components of parts that are characteristic of this disclosure. In this specification, when "the range of numerical values ​​A to numerical values ​​B" is used, that range includes numerical values ​​A and B.

[0015] In the following explanation, when examples are given for the lower and upper limits of numerical values ​​related to specific physical properties or conditions, any combination of either of the given lower limits and any of the given upper limits is permitted, as long as the lower limit does not exceed the upper limit. When multiple materials are given as examples, unless otherwise specified, one type may be selected and used alone, or two or more types may be used in combination.

[0016] This disclosure includes any combination of two or more claims that can be arbitrarily selected from the claims set forth in the attached claims. In other words, any combination of two or more claims that can be arbitrarily selected from the claims set forth in the attached claims is possible, as long as it does not result in a technical inconsistency.

[0017] [Negative electrode for non-aqueous electrolyte secondary battery] The negative electrode for a non-aqueous electrolyte secondary battery according to the embodiments of this disclosure includes a negative electrode mixture layer, the negative electrode mixture layer includes a negative electrode active material and a binder component. In the negative electrode for a non-aqueous electrolyte secondary battery according to the embodiments of this disclosure, the binder component includes a binder compound and a chelating agent.

[0018] In the negative electrode for a non-aqueous electrolyte secondary battery according to the embodiments of this disclosure, when the porosity of the negative electrode mixture layer is ε%, ε satisfies the relationship 5 < ε ≤ 30.

[0019] In the negative electrode for a non-aqueous electrolyte secondary battery according to the embodiments of this disclosure, it is important that (i) the binder component includes a binder compound and a chelating agent, and (ii) when the porosity of the negative electrode mixture layer is ε%, the relationship ε < ε ≤ 30 is satisfied. The reasons for this are explained below.

[0020] The negative electrode for a non-aqueous electrolyte secondary battery typically comprises a negative electrode current collector and a negative electrode mixture layer placed on the negative electrode current collector. The negative electrode mixture layer includes, for example, a negative electrode active material, a binder compound, and a conductive additive. In the negative electrode mixture layer, for example, the negative electrode active materials are connected to each other via the conductive additive, forming conductive paths. In such a negative electrode mixture layer, the negative electrode active material expands during charging and contracts during discharge. Therefore, in a non-aqueous electrolyte secondary battery, the negative electrode mixture layer also repeatedly expands and contracts during charging in accordance with the expansion and contraction of the negative electrode active material.

[0021] In a negative electrode for a non-aqueous electrolyte secondary battery, the greater the porosity of the negative electrode mixture layer, the greater the degree of expansion and contraction of the negative electrode mixture layer. When the degree of expansion and contraction of the negative electrode mixture layer is greater, the effect on the conductive paths formed in the negative electrode mixture layer also increases. When the effect of the expansion and contraction of the negative electrode mixture layer on the conductive paths becomes large, the conductive paths may break off in the negative electrode mixture layer, which can reduce the capacity retention rate of the non-aqueous electrolyte secondary battery. On the other hand, when using a swelling inhibitor to suppress the expansion of the negative electrode mixture layer, it is preferable to allow an appropriate amount of swelling inhibitor to enter the voids in the negative electrode mixture layer in order to obtain a sufficient expansion suppression effect. Therefore, it is preferable that the negative electrode mixture layer has a certain amount of voids that allow an appropriate amount of swelling inhibitor to enter. Also, from the viewpoint of liquid circulation, it is preferable that the negative electrode mixture layer has a certain amount of voids. According to the inventors' diligent research, in the above case, when the porosity of the negative electrode mixture layer is ε%, it is preferable that ε satisfies the relationship 5 < ε ≤ 30.

[0022] Therefore, in order to sufficiently suppress the expansion of the negative electrode mixture layer with an appropriate amount of swelling inhibitor in a negative electrode for a non-aqueous electrolyte secondary battery, it is desirable that the porosity ε of the negative electrode mixture layer satisfies the relationship 5 < ε ≤ 30. Furthermore, from the viewpoint of liquid circulation, it is also desirable that the porosity ε of the negative electrode mixture layer satisfies the above relationship.

[0023] In the negative electrode for a non-aqueous electrolyte secondary battery according to the embodiment of this disclosure, the binder component contained in the negative electrode mixture layer includes a binder compound and a chelating agent, and the binder compound and the chelating agent typically have a structure that can form hydrogen bonds. Therefore, the binder compound and the chelating agent can bond the negative electrode active materials together while forming hydrogen bonds. Furthermore, since the bond formed by hydrogen bonds between the binder compound and the chelating agent is considered to possess both rigidity and elasticity, when the porosity ε of the negative electrode mixture layer satisfies the relationship 5 < ε ≤ 30, it is considered that the presence of an appropriate amount in the voids of the negative electrode mixture layer can reduce the degree of expansion (swelling) of the negative electrode mixture layer during charging. This suppresses the disconnection of conductive paths in the negative electrode mixture layer, thereby suppressing a decrease in the capacity retention rate of the non-aqueous electrolyte secondary battery caused by this. The bond formed by hydrogen bonds between the binder compound and the chelating agent corresponds to a swelling inhibitor.

[0024] The configuration of the negative electrode for a non-aqueous electrolyte secondary battery according to the embodiments of this disclosure will be described in more detail below.

[0025] The negative electrode for a non-aqueous electrolyte secondary battery may include a negative electrode current collector. In this case, the negative electrode mixture layer is placed on the negative electrode current collector. That is, the negative electrode for a non-aqueous electrolyte secondary battery may include a negative electrode current collector and a negative electrode mixture layer placed on the negative electrode current collector. In addition to the negative electrode active material and binder components, the negative electrode mixture layer may contain other additives. Examples of other additives include conductive additives.

[0026] The negative electrode current collector is not particularly limited. For example, a conductive sheet can be used as the negative electrode current collector. Examples of conductive sheets include metal foils such as copper foil, copper alloy foil, and stainless steel foil with copper vapor deposition. Alternatively, a resin sheet with copper vapor deposition (for example, a polyethylene terephthalate sheet) can also be used as the conductive sheet.

[0027] In a negative electrode for a non-aqueous electrolyte secondary battery, when the porosity of the negative electrode mixture layer is ε, the relationship 5 < ε ≤ 30 is satisfied. By satisfying this relationship, the liquid flow of the non-aqueous electrolyte in the negative electrode mixture layer can be improved. Furthermore, the expansion of the negative electrode mixture layer can be sufficiently suppressed by the combination of the binder compound and the chelating agent. It is more preferable that ε satisfies the relationship 7 < ε < 25, and more preferably that ε satisfies the relationship 9 < ε < 20. By satisfying these relationships, it is possible to further sufficiently achieve both the effect of improving the liquid flow of the non-aqueous electrolyte in the negative electrode mixture layer and the effect of suppressing the expansion of the negative electrode mixture layer by the combination of the binder compound and the chelating agent.

[0028] In a negative electrode for a non-aqueous electrolyte secondary battery, the porosity ε of the negative electrode mixture layer is a two-dimensional value obtained from the ratio of the area of ​​voids to the cross-sectional area of ​​each region in the cross-section of the negative electrode mixture layer. The porosity ε of the negative electrode mixture layer can be measured according to the following procedure.

[0029] (1) Disassemble the battery to be evaluated and cut out the negative electrode to expose the cross-section of the negative electrode mixture layer. One method for exposing the cross-section is to cut out a part of the negative electrode and process it with an ion milling device (e.g., Hitachi High-Tech Corporation, IM4000PLUS) to expose the cross-section of the negative electrode mixture layer. (2) Use a SEM to take backscattered electron images of the exposed cross-section of the negative electrode mixture layer for each region of the negative electrode mixture layer. The magnification for taking the backscattered electron images is, for example, 800x. Perform the following processes (3) and (4) for each region of the negative electrode mixture layer and calculate the porosity of each. (3) Import the cross-sectional images obtained in (2) above into a computer and perform binarization processing using image analysis software (e.g., ImageJ, National Institutes of Health, USA) to obtain a binarized image in which the particle cross-sections in the cross-sectional image are made black and the voids present in the particle cross-sections are made white. (4) In the binarized image obtained in (3) above, the area of ​​the voids is calculated by excluding the voids inside the particles (pores not connected to the particle surface) and pores with a width of 3 μm or less that are connected to the particle surface from the voids that have been converted to white. The void ratio ε is calculated based on the following formula: Void ratio ε (%) = Area of ​​voids / Area of ​​each region in the cross-section of the negative electrode mixture layer × 100 (5) The calculation of the void ratio according to (3) and (4) above is performed three times, and the arithmetic mean of the three calculated values ​​is taken as the void ratio of the negative electrode mixture layer.

[0030] As the negative electrode active material, a material that reversibly intercepts and releases lithium ions can be used. Examples of such materials include carbonaceous materials and silicon-containing materials.

[0031] Examples of carbonaceous materials include graphite, easily graphitizable carbon (soft carbon), and difficult-to-graphitize carbon (hard carbon). One type of carbonaceous material may be used alone, or two or more types may be used in combination. Graphite is preferred as the carbonaceous material due to its excellent charge-discharge stability and low irreversible capacity. Examples of graphite include natural graphite, artificial graphite, and graphitized mesophase carbon particles.

[0032] Examples of silicon-containing materials include silicon oxide, silicon, and composite materials. A composite material may contain at least one phase selected from the group consisting of a carbon phase, a lithium silicate phase, a silicon phase, and a silicon oxide phase. One example of a composite material may contain a carbon phase and particulate silicon phase dispersed in the carbon phase. Another example of a composite material may contain a lithium silicate phase and particulate silicon phase dispersed in the lithium silicate phase.

[0033] The negative electrode for a non-aqueous electrolyte secondary battery preferably contains artificial graphite as the negative electrode active material. Furthermore, the negative electrode for a non-aqueous electrolyte secondary battery preferably contains at least one of artificial graphite and a silicon-containing material as the negative electrode active material. Among the negative electrode active materials, artificial graphite and silicon-containing materials have high hardness. Therefore, as will be described later, even if the negative electrode mixture layer is formed by rolling, the voids formed between these active materials are not easily crushed, making it easier to adjust the porosity of the negative electrode mixture layer. In addition to artificial graphite and silicon-containing material, the negative electrode for a non-aqueous electrolyte secondary battery preferably contains natural graphite. In this case, it becomes easier to adjust the porosity ε of the negative electrode mixture layer to satisfy the relationship 5 < ε ≤ 30.

[0034] High-hardness negative electrode active materials, such as graphite and silicon-containing materials, may have a Vickers hardness of 300 Hv or higher, or 500 Hv or higher. The Vickers hardness may be 1000 Hv or lower, or 700 Hv or lower. The Vickers hardness is measured by embedding the negative electrode active material in a thermosetting resin and exposing the cross-section of the negative electrode active material with 400-grit abrasive paper. Furthermore, the cross-section is polished to a mirror finish using 2000-grit abrasive paper. The Vickers hardness of the polished cross-section is measured using a Vickers hardness tester with a load of 1 kg and a holding time of 15 seconds.

[0035] When the negative electrode mixture layer contains at least one of artificial graphite and silicon-containing material as the negative electrode active material, it is preferable that a and b satisfy the following relationships: 0 ≤ a ≤ 90 and 10a + b ≥ 80, where a mass% is the mass ratio of the silicon-containing material to the total negative electrode active material, and b mass% is the mass ratio of the artificial graphite to the total negative electrode active material. By including the silicon-containing material and artificial graphite in the negative electrode mixture layer in such a way that satisfies the above relationships, the decrease in the capacity retention rate of the non-aqueous electrolyte secondary battery can be further sufficiently suppressed.

[0036] When the negative electrode mixture layer contains a silicon-containing material and artificial graphite as an optional component as the negative electrode active material, if the total negative electrode active material is 100% by mass, the mass ratio of the silicon-containing material to the total negative electrode active material is a% by mass, and the mass ratio of the artificial graphite to the total negative electrode active material is b% by mass, then it is preferable that a and b satisfy the relationship 5 < a < 85 and 3a + b ≥ 60. By including the silicon-containing material and artificial graphite in the negative electrode mixture layer in such a way that satisfies the above relationship, the decrease in the capacity retention rate of the non-aqueous electrolyte secondary battery can be further sufficiently suppressed.

[0037] The binder compound included in the binder component is preferably a compound that binds to the chelating agent. Examples of such bonds include covalent bonds, ionic bonds, and hydrogen bonds, but hydrogen bonds are preferred. The binder compound preferably contains at least one selected from the group consisting of polyacrylic acid and salts of polyacrylic acid. Examples of cations constituting the salt of a salt of polyacrylic acid include lithium ions, sodium ions, potassium ions, and ammonium ions. The weight-average molecular weight of the binder compound may be in the range of 5,000 to 5,000,000 or in the range of 100,000 to 1,000,000.

[0038] The chelating agent contained in the binder component preferably contains at least one functional group selected from the group consisting of carboxylic acid groups, carboxylic acid bases, phosphonic acid groups, and phosphonic acid bases. Examples of cations constituting the salt in carboxylic acid bases and phosphonic acid bases include lithium ions, sodium ions, potassium ions, and ammonium ions. The chelating agent preferably contains at least one selected from the group consisting of ethylenediamine derivatives, bisphosphonate derivatives, and inositol derivatives. Examples of ethylenediamine derivatives include the compound shown in the following chemical formula (1), examples of bisphosphonate derivatives include the compound shown in the following chemical formula (2), and examples of inositol derivatives include the compound shown in the following chemical formula (3).

[0039]

[0040]

[0041]

[0042] In the negative electrode mixture layer, when the binder compound content is Wp and the chelating agent content is Wc, it is preferable that the ratio of Wc to Wp (Wc / Wp) satisfies the relationship 0.01 ≤ Wc / Wp ≤ 0.75. By satisfying this relationship, a suitable bond can be formed in the negative electrode mixture layer by hydrogen bonding between the binder compound and the chelating agent. As a result, even when the porosity ε of the negative electrode mixture layer satisfies the relationship 5 < ε ≤ 30, the expansion of the negative electrode mixture layer during charging and discharging can be sufficiently suppressed.

[0043] The binder component may contain polyvalent cations. If the binder component contains polyvalent cations, when the chelating agent is a phosphorus-containing compound as shown in chemical formulas (2) and (3) above, the phosphorus-containing compounds can be linked together via the polyvalent cations. This also helps to suppress the expansion of the negative electrode mixture layer. The polyvalent cations may be incorporated into the binder component, for example, by incorporating them into a non-aqueous electrolyte and allowing these polyvalent cations to permeate the negative electrode mixture layer.

[0044] A polyvalent cation is a cation with a valence of 2 or more. Examples of polyvalent cations include divalent cations, trivalent cations, and tetravalent cations. The polyvalent cation may include at least one selected from the group consisting of Ca ２＋ , Mg ２＋ , Ba ２＋ , Ge ２＋ , Cu ２＋ , Ni ２＋ , Co ２＋ , Sn ２＋ , Sr ２＋ , Zn ２＋ , Pd ２＋ , Pt ２＋ , Mn ２＋ , Mn ３＋ , Ti ３＋ , Nb ３＋ , Bi ３＋ , Ce ３＋ , Cr ３＋ , La ３＋ , In ３＋ , Rh ３＋ , Sb ３＋ , Sm ３＋ , Dy ３＋ , Eu ３＋ , Mn ３＋ , Fe ３＋ , Al ３＋ , Hf ４＋ , Zr ４＋ , and Th ４＋ and may contain at least one selected from the group consisting of. The polyvalent cation may be any one selected from the above group.

[0045] The polyvalent cation may contain a divalent cation or may be a divalent cation. Divalent cations are considered to easily and stably bond phosphorus-containing compounds to each other. The polyvalent cation may include at least one selected from the group consisting of Ca[[ID=​​​​​​​​​​​​​Conductive carbon materials can be used as conductive materials. Examples of conductive carbon materials include carbon black, carbon nanotubes, and graphite.

[0047] [Non-aqueous electrolyte secondary battery] A non-aqueous electrolyte secondary battery according to an embodiment of this disclosure comprises a positive electrode, a negative electrode, and a non-aqueous electrolyte. In the non-aqueous electrolyte secondary battery according to an embodiment of this disclosure, the negative electrode is a negative electrode for a non-aqueous electrolyte secondary battery according to an embodiment of this disclosure. In addition to the positive electrode, negative electrode, and non-aqueous electrolyte, the non-aqueous electrolyte secondary battery according to an embodiment of this disclosure may also include a separator interposed between the positive electrode and the negative electrode, and an outer casing. Examples of non-aqueous electrolyte secondary batteries include lithium-ion secondary batteries and lithium metal secondary batteries. The components other than the negative electrode will be described below.

[0048] (Positive electrode) The positive electrode includes a positive electrode mixture layer. The positive electrode may also include a positive electrode current collector and a positive electrode mixture layer disposed on the positive electrode current collector. The positive electrode current collector and the positive electrode mixture layer are not particularly limited, and those used in the positive electrodes of various known non-aqueous electrolyte secondary batteries may be used.

[0049] Examples of materials that constitute the positive electrode current collector include metallic materials such as Al, Ti, and Fe. The metallic material may also be Al, Al alloy, Ti, Ti alloy, and Fe alloy. The Fe alloy may be stainless steel (SUS).

[0050] The positive electrode mixture layer contains a positive electrode active material. As the positive electrode active material, a substance that reversibly intercepts and releases lithium ions can be used. Examples of positive electrode active materials include composite oxides containing lithium and a metal element other than lithium (Me), transition metal fluorides, polyanions, fluorinated polyanions, and transition metal sulfides. The composite oxide containing lithium and the metal element Me may be a lithium-containing transition metal oxide containing at least a transition metal as the metal element Me. Because it has low manufacturing costs and a high average discharge voltage, it is preferable to use a lithium-containing transition metal oxide as the positive electrode active material.

[0051] Examples of transition metal elements included in lithium-containing transition metal oxides include Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Y, Zr, and W. A lithium-containing transition metal oxide may contain one transition metal element or two or more transition metal elements. Preferably, a lithium-containing transition metal oxide contains at least one element selected from the group consisting of Ni, Co, Mn, and Al.

[0052] The positive electrode mixture layer may contain additives other than the positive electrode active material. Examples of additives include binder compounds (binding agents) and conductive materials. Examples of binder compounds include fluororesins, polyacrylonitrile, polyimide resins, acrylic resins, polyolefin resins, and rubbery polymers. Examples of fluororesins include polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF). Conductive materials can be conductive carbon materials. Examples of conductive carbon materials include carbon black, carbon nanotubes, and graphite.

[0053] (Separator) As the separator, a porous sheet having ion permeability and insulating properties can be used. As the porous sheet, for example, a thin film, woven fabric, and nonwoven fabric having microporous properties can be used. The material constituting the separator is not particularly limited, and for example, polymer materials can be used. Examples of polymer materials include polyolefin resins, polyamide resins, and cellulose. Examples of polyolefin resins include polyethylene resins, polypropylene resins, and copolymers of ethylene and propylene. The separator may contain additives (such as inorganic fillers) as needed. The thickness of the separator is not particularly limited and may be 10 μm or more, or 15 μm or more. The thickness of the separator may be 30 μm or less, or 20 μm or less.

[0054] (Non-aqueous electrolyte) As the non-aqueous electrolyte, a non-aqueous electrolyte having lithium ion conductivity can be used. The non-aqueous electrolyte contains a non-aqueous solvent and ions dissolved in the non-aqueous solvent. Examples of ions include lithium ions and anions. The non-aqueous electrolyte may be in liquid or gel form.

[0055] Non-aqueous electrolytes can be prepared by dissolving lithium salts in a non-aqueous solvent. By dissolving lithium salts in a non-aqueous solvent, lithium ions and anions can be generated. Furthermore, by dissolving salts of polyvalent cations in a non-aqueous solvent, polyvalent cations and anions can also be generated.

[0056] Examples of lithium salts include lithium salts of chlorine-containing acids (e.g., LiClO ４ LiAlCl ４ , and LiB １０ Cl １０ (e.g., lithium salts of fluorine-containing acids (e.g., LiPF)) ６ LiPF ２ O ２ LiBF ４ LiSbF ６ LiAsF ６ LiCF ３ SO ３ , and LiCF ３ CO ２ (e.g., lithium salts of fluorine-containing acidimides (e.g., LiN(FSO)) ２ ) ２ ,LiN(CF ３ SO ２ ) ２ ,LiN(CF ３ SO ２ ) (C ４ F ９ SO ２ ), and LiN(C ２ F ５ SO ２ ) ２Examples include lithium halides (e.g., LiCl, LiBr, and LiI). The lithium salt may be used alone or in combination of two or more types. The concentration of the lithium salt in the non-aqueous electrolyte is, for example, 0.5 mol / L or more and 3.5 mol / L or less.

[0057] Non-aqueous electrolytes may be substantially free of chloride ions. For example, the concentration of chloride ions in a non-aqueous electrolyte may be less than 0.001 mol / L or less than 0.0001 mol / L. Non-aqueous electrolytes that are substantially free of chloride ions are preferable in that they substantially do not generate chlorine-based gases derived from chloride ions during the charging and discharging process. Non-aqueous electrolytes that are substantially free of chloride ions can be prepared by using salts that do not contain the element chlorine.

[0058] The non-aqueous solvent is not particularly limited, and various known non-aqueous solvents can be used. Examples of non-aqueous solvents include cyclic carbonate esters, linear carbonate esters, cyclic carboxylic acid esters, and linear carboxylic acid esters. Examples of cyclic carbonate esters include propylene carbonate (PC), ethylene carbonate (EC), fluoroethylene carbonate (FEC), and vinylene carbonate (VC). Examples of linear carbonate esters include dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC). Examples of cyclic carboxylic acid esters include γ-butyrolactone (GBL) and γ-valerolactone. Examples of linear carboxylic acid esters include methyl acetate, ethyl acetate, propyl acetate, methyl propionate, and ethyl propionate. The non-aqueous solvent may be used alone or in combination of two or more types.

[0059] The non-aqueous electrolyte may contain various known additives. Examples of additives include 1,3-propanesalton, methylbenzenesulfonate, cyclohexylbenzene, biphenyl, diphenyl ether, and fluorobenzene. Cyclic carbonate esters such as vinylene carbonate (VC) and fluoroethylene carbonate (FEC), which were exemplified as solvents, may also be used as additives.

[0060] (Outer casing) Various known outer casings (battery cases) can be used. The outer casing may include an outer can and a sealing body that seals the opening of the outer can. In this case, the outer can functions as the negative terminal, and the sealing body functions as the positive terminal. The sealing body may include a sealing plate and a gasket.

[0061] The outer casing (battery case) houses the electrode group and the non-aqueous electrolyte. The electrode group consists of a positive electrode, a negative electrode, and a separator interposed between the positive and negative electrodes. The configuration of the electrode group is not particularly limited. The electrode group may be wound or laminated. A wound electrode group is formed by winding a laminate of a positive electrode, a negative electrode, and a separator interposed between the positive and negative electrodes. The form of the non-aqueous electrolyte secondary battery is not particularly limited. The form of the non-aqueous electrolyte secondary battery may be cylindrical, prismatic, coin-shaped, button-shaped, or laminated.

[0062] Hereinafter, an example of a non-aqueous electrolyte secondary battery according to one embodiment of the present disclosure will be described with reference to the drawings. The components of the example described below can be the components described above. Furthermore, the components of the example described below can be modified based on the above description. In addition, the matters described below may be applied to the above embodiment. Furthermore, in the example described below, components that are not essential to the non-aqueous electrolyte secondary battery according to the present disclosure may be omitted.

[0063] Figure 1 is a schematic longitudinal cross-sectional view showing a non-aqueous electrolyte secondary battery according to one embodiment of the present disclosure. The non-aqueous electrolyte secondary battery 10 shown in Figure 1 has a cylindrical shape. The non-aqueous electrolyte secondary battery 10 includes a cylindrical battery case and an electrode group 14 and a non-aqueous electrolyte (not shown) housed within the battery case. The electrode group 14 is a wound electrode group and includes a positive electrode 11, a negative electrode 12, and a separator 13 interposed between the positive electrode 11 and the negative electrode 12. The wound electrode group is formed by winding a laminate of the positive electrode 11, the negative electrode 12, and the separator 13.

[0064] The battery case includes a case body 15, which is a bottomed cylindrical metal container, and a sealing body 16 that seals the opening of the case body 15. A gasket 27 is placed between the case body 15 and the sealing body 16. The placement of the gasket 27 ensures that the battery case is airtight. Inside the case body 15, insulating plates 17 and 18 are placed at both ends of the electrode group 14 in the direction of the winding axis, respectively. The case body 15 has a stepped portion 21.

[0065] The sealing body 16 includes a filter 22, a lower valve body 23, an insulating member 24, an upper valve body 25, and a cap 26. The lower valve body 23 and the upper valve body 25 are connected at their respective centers. The insulating member 24 is positioned between the peripheral edge of the lower valve body 23 and the peripheral edge of the upper valve body 25. The filter 22 and the lower valve body 23 are connected at their respective peripheral edges. The upper valve body 25 and the cap 26 are connected at their respective peripheral edges. Of the components of the sealing body 16, all components except the insulating member 24 are electrically connected.

[0066] The lower valve body 23 has a ventilation hole. Therefore, if the internal pressure of the battery case rises due to abnormal heat generation or other reasons, the upper valve body 25 bulges towards the cap 26 and separates from the lower valve body 23. This disconnects the electrical connection between the lower valve body 23 and the upper valve body 25. If the internal pressure rises further, the upper valve body 25 ruptures, and gas is released through the opening formed in the cap 26.

[0067] The positive electrode 11 is electrically connected to the cap 26, which functions as a positive electrode terminal, via the positive electrode lead 19. The negative electrode 12 is electrically connected to the case body 15, which functions as a negative electrode terminal, via the negative electrode lead 20. The negative electrode 12 is the negative electrode for a non-aqueous electrolyte secondary battery according to the embodiment of this disclosure.

[0068] [Method for Manufacturing a Non-Aqueous Electrolyte Secondary Battery] A method for manufacturing a non-aqueous electrolyte secondary battery according to one embodiment of the present disclosure will be described below. In the following description, an example will be described in which the negative electrode includes a negative electrode current collector and a negative electrode mixture layer disposed on the negative electrode current collector, and a separator is interposed between the negative electrode and the positive electrode.

[0069] (First step) The first step includes a first substep for manufacturing a negative electrode, a second substep for manufacturing a positive electrode, and a third substep for manufacturing an electrode group by interposing a separator between the positive electrode and the negative electrode.

[0070] In the first substep, a negative electrode mixture containing a negative electrode active material and a binder component is mixed with a dispersion medium to prepare a negative electrode mixture slurry. As the dispersion medium, for example, water, alcohol (e.g., ethanol), ether (e.g., tetrahydrafuran), N-methyl-2-pyrrolidone (NMP), or a mixture thereof can be used. The negative electrode active material preferably contains at least one of artificial graphite and a silicon-containing material. The negative electrode mixture may optionally contain other substances besides the negative electrode active material and binder component.

[0071] Next, a negative electrode mixture slurry is applied to the negative electrode current collector to obtain a coating film, and this coating film is dried to obtain a laminate containing the negative electrode current collector and a negative electrode mixture layer placed on the negative electrode current collector. Next, the negative electrode is manufactured by rolling this laminate. The thickness of the negative electrode mixture layer may be 3 μm or more, or 5 μm or more. The thickness of the negative electrode mixture layer may be 200 μm or less, or 150 μm or less. The negative electrode may be cut to a predetermined size as needed. The negative electrode mixture layer may be formed on only one side of the negative electrode current collector, or on both sides.

[0072] The second substep can be carried out in the same manner as the first substep, except that a positive electrode mixture slurry is used instead of a negative electrode mixture slurry, and a positive electrode current collector is used instead of a negative electrode current collector. The positive electrode mixture slurry contains a positive electrode active material, a binder compound (binding agent), and a conductive material as the positive electrode mixture, and further contains a dispersion medium. As the dispersion medium, those exemplified in the first substep can be used.

[0073] In the third substep, as described above, an electrode group is fabricated by interposing a separator between the positive and negative electrodes. The electrode group may be of the wound type or the stacked type. A wound electrode group is fabricated by winding the positive electrode, negative electrode, and separator together. A stacked electrode group is fabricated by stacking one or more flat positive electrodes, one or more flat negative electrodes, and one or more flat separators so that their main surfaces overlap. In both the wound and stacked electrode groups, a separator is interposed between the positive and negative electrodes.

[0074] (Second Step) In the second step, the electrode group and the non-aqueous electrolyte are housed inside the outer casing. The method for housing the electrode group and the non-aqueous electrolyte inside the outer casing is not particularly limited, and various known methods can be employed. The non-aqueous electrolyte can be prepared, for example, by dissolving predetermined components (salts, additives, etc.) in a non-aqueous solvent. The outer casing is not particularly limited, and various known outer casings can be used.

[0075] (Note) The following technologies are disclosed by the above description. (Technology 1) A negative electrode for a non-aqueous electrolyte secondary battery, comprising a negative electrode mixture layer, wherein the negative electrode mixture layer comprises a negative electrode active material and a binder component, wherein the binder component comprises a binder compound and a chelating agent, and when the porosity of the negative electrode mixture layer is ε%, ε satisfies the relationship 5 < ε ≤ 30. (Technology 2) The negative electrode for a non-aqueous electrolyte secondary battery according to Technology 1, wherein the binder compound comprises at least one selected from the group consisting of polyacrylic acid and salts of polyacrylic acid. (Technology 3) The negative electrode for a non-aqueous electrolyte secondary battery according to Technology 1 or 2, wherein ε satisfies the relationship 7 < ε < 25. (Technology 4) The negative electrode for a non-aqueous electrolyte secondary battery according to any one of Technology 1 to 3, wherein the negative electrode active material comprises artificial graphite. (Technology 5) The negative electrode for a non-aqueous electrolyte secondary battery according to any one of Technologies 1 to 4, wherein ε satisfies the relationship 9 < ε < 20. (Technology 6) The negative electrode mixture layer comprises, as the negative electrode active material, at least one of artificial graphite and a silicon-containing material, wherein when the total negative electrode active material is 100% by mass, the mass ratio of the silicon-containing material to the total negative electrode active material is a% by mass, and the mass ratio of the artificial graphite to the total negative electrode active material is b% by mass, then a and b satisfy the relationship 0 ≤ a ≤ 90 and 10a + b ≥ 80. The negative electrode for a non-aqueous electrolyte secondary battery according to any one of Technologies 1 to 5. (Technical 7) The negative electrode mixture layer comprises a silicon-containing material and artificial graphite as an optional component as the negative electrode active material, wherein when the total negative electrode active material is 100% by mass, the mass ratio of the silicon-containing material to the total negative electrode active material is a% by mass, and the mass ratio of the artificial graphite to the total negative electrode active material is b% by mass, then a and b satisfy the relationship 5 < a < 85 and 3a + b ≥ 60, the negative electrode for a non-aqueous electrolyte secondary battery according to any one of Technical 1 to 5. (Technical 8) The chelating agent comprises at least one functional group selected from the group consisting of a carboxylic acid group, a carboxylic acid base, a phosphonic acid group, and a phosphonic acid base, the negative electrode for a non-aqueous electrolyte secondary battery according to any one of Technical 1 to 7.(Technology 9) The negative electrode for a non-aqueous electrolyte secondary battery according to any one of Technology 1 to 8, wherein the chelating agent comprises at least one selected from the group consisting of ethylenediamine derivatives, bisphosphonate derivatives, and inositol derivatives. (Technology 10) The negative electrode for a non-aqueous electrolyte secondary battery according to any one of Technology 1 to 9, wherein in the negative electrode mixture layer, when the content of the binder compound is Wp and the content of the chelating agent is Wc, the ratio of Wc to Wp (Wc / Wp) satisfies the relationship 0.01 ≤ Wc / Wp ≤ 0.75. (Technology 11) A non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte, wherein the negative electrode is the negative electrode for a non-aqueous electrolyte secondary battery according to any one of Technology 1 to 10.

[0076] The present disclosure will be described below in detail based on examples and comparative examples, but the present disclosure is not limited to the following examples.

[0077] (Example 1) (1) Preparation of the negative electrode A negative electrode slurry was prepared by mixing the negative electrode active material, polyacrylic acid (PAA), styrene-butadiene copolymer rubber (SBR), carboxymethylcellulose (CMC), carbon nanotubes (CNT), ethylenediaminetetraacetic acid (EDTA), and an appropriate amount of water. The negative electrode active material contained silicon-containing material, natural graphite, and artificial graphite in the mass % shown in Table 1 below. As the silicon-containing material, silicon-carbon composite particles (GSS manufactured by Giga Solar Materials) were used. This silicon-carbon composite material contains a carbon phase and a particulate silicon phase dispersed in the carbon phase. The mass ratio of the negative electrode active material, PAA, SBR, CMC, CNT, and EDTA was set to negative electrode active material:PAA:SBR:CMC:CNT:EDTA = 100:1:1:1:0.1:0.1.

[0078] A negative electrode mixture slurry was applied to one side of an electrolytic copper foil (current collector) to form a coating film, thereby obtaining a laminate of the electrolytic copper foil and the coating film. Next, this laminate was punched out to a predetermined size (2 cm x 2 cm) and then dried. In this way, a negative electrode containing a negative electrode mixture layer was obtained. At nine locations on the fabricated negative electrode, the initial thickness T(0) of the negative electrode mixture layer was measured. １~T(0) ９ The value was measured. A lead was attached to the negative electrode.

[0079] (2) Fabrication of the counter electrode A lithium metal foil was attached to one side of an electrolytic copper foil (current collector), and then the counter electrode was fabricated by punching out a square shape with sides of 2.5 cm. Leads were also attached to the counter electrode.

[0080] (3) Preparation of non-aqueous electrolyte Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) were mixed in a volume ratio of EC:EMC:DMC = 4:1:15 to obtain a non-aqueous solvent. LiPF ６ It was dissolved at a concentration of 1.3 mol / L. In this way, a non-aqueous electrolyte was prepared.

[0081] (4) Test cell assembly An electrode group was fabricated by arranging the negative electrode and counter electrode prepared as described above opposite each other via a separator. A microporous film made of polyolefin was used as the separator. Next, the electrode group was housed inside an outer casing. An outer casing made of aluminum laminate sheet was used. Next, the non-aqueous electrolyte prepared as described above was injected into the inside of the outer casing, and then the opening of the outer casing was sealed. At this time, a portion of the lead attached to the negative electrode and a portion of the lead attached to the counter electrode were exposed from the outer casing. In this way, the test cell according to Example 1 was fabricated.

[0082] (Example 2) In preparing the negative electrode, a silicon-containing material and natural graphite were used as the negative electrode active material, as shown in Table 1 below, and the mass % of each was as shown in Table 1 below. Otherwise, a test cell according to Example 2 was prepared in the same manner as in Example 1.

[0083] (Example 3) In preparing the negative electrode, a test cell according to Example 3 was prepared in the same manner as in Example 1, except that the negative electrode active material used contained silicon-containing material, natural graphite, and artificial graphite in the mass % shown in Table 1 below.

[0084] (Example 4) In preparing the negative electrode, a test cell according to Example 4 was prepared in the same manner as in Example 2, except that the negative electrode active material used contained silicon-containing material and natural graphite in the mass % shown in Table 1 below.

[0085] (Example 5) In preparing the negative electrode, a test cell according to Example 5 was prepared in the same manner as in Example 1, except that the negative electrode active material used contained silicon-containing material, natural graphite, and artificial graphite in the mass % shown in Table 1 below.

[0086] (Example 6) In preparing the negative electrode, a test cell according to Example 6 was prepared in the same manner as in Example 2, except that the negative electrode active material used contained silicon-containing material and natural graphite in the mass % shown in Table 1 below.

[0087] (Example 7) In preparing the negative electrode, a test cell according to Example 7 was prepared in the same manner as in Example 1, except that the negative electrode active material used contained silicon-containing material, natural graphite, and artificial graphite in the mass % shown in Table 1 below.

[0088] (Example 8) In preparing the negative electrode, a test cell according to Example 8 was prepared in the same manner as in Example 1, except that the negative electrode active material used contained silicon-containing material, natural graphite, and artificial graphite in the mass % shown in Table 1 below.

[0089] (Example 9) In preparing the negative electrode, a test cell according to Example 9 was prepared in the same manner as in Example 2, except that the negative electrode active material used contained silicon-containing material and natural graphite in the mass % shown in Table 1 below.

[0090] (Example 10) In preparing the negative electrode, a test cell according to Example 10 was prepared in the same manner as in Example 2, except that the negative electrode active material used contained silicon-containing material and natural graphite in the mass % shown in Table 1 below.

[0091] (Example 11) In preparing the negative electrode, a test cell according to Example 11 was prepared in the same manner as in Example 2, except that the negative electrode active material used contained silicon-containing material and natural graphite in the mass % shown in Table 1 below.

[0092] (Comparative Example 1) A test cell according to Comparative Example 1 was prepared in the same manner as in Example 1, except that the negative electrode active material used contained silicon-containing material, natural graphite, and artificial graphite in the mass % shown in Table 1 below.

[0093] (Comparative Example 2) A test cell according to Comparative Example 2 was prepared in the same manner as in Example 2, except that the negative electrode active material used contained silicon-containing material and natural graphite in the mass percentages shown in Table 1 below.

[0094] Table 1 is shown below. In addition to the mass percentages of silicon-containing material, natural graphite, and artificial graphite, Table 1 also shows the porosity ε of the negative electrode mixture layer. The porosity ε of the negative electrode mixture layer was measured according to the method described in the Embodiments section above.

[0095]

[0096] Test cells corresponding to Reference Examples 1 to 13 were also prepared. The test cells corresponding to Reference Examples 1 to 11 were prepared in the same manner as the test cells corresponding to Examples 1 to 11, except that EDTA was not included in the negative electrode mixture layer. The test cells corresponding to Reference Examples 12 and 13 were prepared in the same manner as the test cells corresponding to Comparative Examples 1 and 2, except that EDTA was not included in the negative electrode mixture layer.

[0097] For the test cells related to Reference Examples 1 to 13, the initial thickness T(0) of the negative electrode mixture layer was measured at nine locations on the negative electrode, in the same manner as described above. １ ~T(0) ９ We measured it.

[0098] [Evaluation] <Initial Capacity> The test cells for each example (Examples 1-11, Comparative Examples 1 and 2, and Reference Examples 1-13) were left in an environment of 25°C, and constant current charging was performed with a current of 0.5 It until the voltage reached 4.2 V. Then, constant voltage charging was performed with a constant voltage of 4.2 V until the current reached 0.02 It. Next, constant current discharge was performed with a current of 1.0 It until the voltage reached 2.5 V. The discharge capacity during the first discharge performed in this manner was defined as the initial capacity C. ０ This was the request.

[0099] <Capacity Retention Rate> After the initial discharge, the test cells for each example were left for 20 minutes, and then the charge-discharge cycle was repeated 300 times. In the charge-discharge cycle, (1) constant current charging was performed with a current of 1.0 It until the voltage reached 4.2 V, followed by constant voltage charging at a constant voltage of 4.2 V until the current reached 0.02 It, and (2) constant current discharge was performed with a current of 1.0 It until the voltage reached 2.5 V, and this was repeated.

[0100] After repeating the charge-discharge cycle 300 times, the discharge capacity at the 300th discharge is defined as discharge capacity C. ３００ It was measured as follows. The obtained initial capacity C ０ and discharge capacity C ３００ Using the following formula (1), the capacity retention rate X (%) was calculated. Then, the capacity retention rate X was evaluated as the cycle retention rate. Then, the capacity retention rate X (X) of the test cell related to the corresponding reference example was calculated. Ｒ The volume retention rate of the test cell for each example (X) Ｅ ) difference (X Ｅ -X Ｒ The difference in capacity retention rate was calculated. Note that the larger the difference in capacity retention rate, the better the capacity is maintained. Also, Examples 1 to 11 correspond to Reference Examples 1 to 11, respectively, and Comparative Examples 1 and 2 correspond to Reference Examples 12 and 13, respectively. For example, for the test cell according to Example 1, the difference in capacity retention rate with the test cell according to Comparative Example 1 was calculated. ・Capacity retention rate X (%) = (C ３００ / C ０ ) × 100 ... (1)

[0101] <Expansion> For each example, the test cells were charged in a constant temperature bath at 25°C as follows.

[0102] For each test cell according to each example (Examples 1 to 11, Comparative Examples 1 and 2, and Reference Examples 1 to 13), constant current charging was performed at a current value of 0.1 C (1 C is the current value for discharging the design capacity in 1 hour) until the voltage reached 0.005 V. The subsequent rest time was 20 minutes. Next, constant current charging was performed at a current value of 0.01 C until the voltage reached 0.005 V. The subsequent rest time was 20 minutes. Further, constant current charging was performed at a current value of 0.001 C until the voltage reached 0.005 V.

[0103] After charging, each test cell according to each example was disassembled to take out the negative electrode, and then for each, at nine measurement locations identical to those of T(0) １ to T(0) ９ the thickness T(C) １ to T(C) ９ of the negative electrode mixture layer in the fully charged state was measured. Then, using the following formula, the swelling ratio Y １ to Y ９ of the negative electrode at full charge was calculated, and the calculated values were averaged. Thereby, for each test cell according to each example, the average swelling ratio Y (%) of the negative electrode at full charge was obtained. As described above, the thickness T(0) ｎ is the initial thickness of the negative electrode mixture layer. Here, n is an integer from 1 to 9. And the difference (Y Ｒ -Y Ｅ ) between the average swelling ratio (Y Ｒ ) of the negative electrode according to the corresponding reference example and the average swelling ratio Y (Y Ｅ ) of the negative electrode according to each example was obtained. Note that the greater the difference in the average swelling ratio, the more the swelling of the negative electrode mixture layer is suppressed. Also, Examples 1 to 11 correspond to Reference Examples 1 to 11 respectively, and Comparative Examples 1 and 2 correspond to Reference Examples 12 and 13 respectively. Therefore, for example, for the negative electrode according to Example 1, the difference in the average swelling ratio from the negative electrode according to Comparative Example 1 was obtained. - Swelling ratio Yn (%) = (thickness T(C) <……> / thickness T(0) <……>) × 100

[0104] The results of evaluating the difference in the average swelling ratio and the difference in the capacity retention rate for each test cell according to each example are shown in Table 2 below.

[0105]

[0106] Table 2 shows that the test cells in each example (Examples 1 to 11) yielded better results in terms of the difference in average expansion rate and the difference in volume retention rate compared to the test cells in Reference Examples 1 to 11. Furthermore, the test cells in Examples 5 to 11 yielded particularly good results in terms of the difference in average expansion rate and the difference in volume retention rate. In contrast, the test cells in Comparative Examples 1 and 2 did not show any improvement in terms of the difference in average expansion rate and the difference in volume retention rate compared to the test cells in Reference Examples 12 and 13.

[0107] Although the present invention has been described in relation to preferred embodiments at present, such disclosure should not be interpreted restrictively. Various modifications and alterations will undoubtedly become apparent to those skilled in the art in the field to which the invention pertains by reading the above disclosure. Accordingly, the appended claims should be interpreted as encompassing all modifications and alterations without departing from the true spirit and scope of the invention.

[0108] The negative electrode for non-aqueous electrolyte secondary batteries relating to this disclosure can be used in applications where it is required to suppress a decrease in the capacity retention rate of non-aqueous electrolyte secondary batteries.

[0109] 10: Non-aqueous electrolyte secondary battery, 11: Positive electrode, 12: Negative electrode, 13: Separator, 14: Electrode group

Claims

1. A negative electrode for a non-aqueous electrolyte secondary battery, comprising a negative electrode mixture layer, wherein the negative electrode mixture layer comprises a negative electrode active material and a binder component, the binder component comprises a binder compound and a chelating agent, and when the porosity of the negative electrode mixture layer is ε%, the relationship ε < ε ≤ 30 is satisfied.

2. The negative electrode for a non-aqueous electrolyte secondary battery according to claim 1, wherein the binder compound comprises at least one selected from the group consisting of polyacrylic acid and salts of polyacrylic acid.

3. The negative electrode for a non-aqueous electrolyte secondary battery according to claim 1, wherein ε satisfies the relationship 7 < ε < 25.

4. The negative electrode for a non-aqueous electrolyte secondary battery according to claim 1, wherein the negative electrode active material contains artificial graphite.

5. The negative electrode for a non-aqueous electrolyte secondary battery according to claim 1, wherein ε satisfies the relationship 9 < ε < 20.

6. The negative electrode mixture layer comprises, as the negative electrode active material, at least one of artificial graphite and a silicon-containing material, wherein when the total negative electrode active material is 100% by mass, the mass ratio of the silicon-containing material to the total negative electrode active material is a% by mass, and the mass ratio of the artificial graphite to the total negative electrode active material is b% by mass, then a and b satisfy the relationship 0 ≤ a ≤ 90 and 10a + b ≥ 80, the negative electrode for a non-aqueous electrolyte secondary battery according to claim 1.

7. The negative electrode mixture layer comprises, as the negative electrode active material, a silicon-containing material and, as an optional component, artificial graphite, wherein when the total negative electrode active material is 100% by mass, the mass ratio of the silicon-containing material to the total negative electrode active material is a% by mass, and the mass ratio of the artificial graphite to the total negative electrode active material is b% by mass, then a and b satisfy the relationship 5 < a < 85 and 3a + b ≥ 60, the negative electrode for a non-aqueous electrolyte secondary battery according to claim 1.

8. The negative electrode for a non-aqueous electrolyte secondary battery according to claim 1, wherein the chelating agent comprises at least one functional group selected from the group consisting of a carboxylic acid group, a carboxylic acid base, a phosphonic acid group, and a phosphonic acid base.

9. The negative electrode for a non-aqueous electrolyte secondary battery according to claim 1, wherein the chelating agent comprises at least one selected from the group consisting of ethylenediamine derivatives, bisphosphonate derivatives, and inositol derivatives.

10. The negative electrode for a non-aqueous electrolyte secondary battery according to claim 1, wherein, in the negative electrode mixture layer, when the content of the binder compound is Wp and the content of the chelating agent is Wc, the ratio of Wc to Wp (Wc / Wp) satisfies the relationship 0.01 ≤ Wc / Wp ≤ 0.

75.

11. A non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte, wherein the negative electrode is a negative electrode for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 10.

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