JP7560655B2 - Composition for negative electrode, negative electrode sheet and non-aqueous secondary battery, and method for producing the negative electrode sheet and non-aqueous secondary battery - Google Patents

Description

The present invention relates to a negative electrode composition, a negative electrode sheet, a non-aqueous secondary battery, a method for manufacturing a negative electrode sheet, and a method for manufacturing a non-aqueous secondary battery.

Secondary batteries, such as lithium-ion secondary batteries, are used as power sources for portable electronic devices such as personal computers, video cameras, and mobile phones. In recent years, against the backdrop of the global environmental challenge of reducing carbon dioxide emissions, they have become increasingly popular as power sources for automobiles and other transportation equipment, and for storing electricity such as nighttime electricity and electricity generated by natural energy sources.

The electrodes (positive and negative electrodes) of a lithium-ion secondary battery have electrode active material layers (positive and negative active material layers), which contain electrode active material particles that can absorb or release lithium ions during charging and discharging. In addition, electrons are transported between the electrode active material particles, or between the electrode active material particles and the current collector, so it is necessary to ensure electronic conductivity. To improve the efficiency of this electronic conduction, the adhesion between the electrode active material particles, or between the electrode active material particles and the current collector, is important, and the electrode active material layers usually contain a binder.

In order to realize high-capacity lithium-ion secondary batteries, the use of silicon oxide as the negative electrode active material has been actively investigated. The theoretical capacity of silicon oxide is much higher than that of graphite, etc., and it is possible to achieve high energy density of the battery.
When silicon oxide is used as the negative electrode active material, it absorbs a large amount of lithium ions and expands significantly during charging, and the silicon oxide also contracts significantly during discharging. Therefore, in lithium-ion batteries using silicon oxide as the negative electrode active material, the volume of the negative electrode active material changes significantly during charging and discharging, and the battery performance is easily degraded by repeated charging and discharging. In other words, there is a limit to improving the cycle life.
As a technique for addressing such problems, for example, Patent Document 1 describes a slurry for a lithium-ion battery anode, which contains a negative electrode active material containing 20 mass% or more of silicon particles having a median diameter of 0.1 to 2 μm, poly(meth)acrylamide which is a radical copolymer of a monomer group including a (meth)acrylamide skeleton-containing monomer and a sulfonic acid group-substituted unsaturated hydrocarbon group-containing monomer and exhibits a specific high viscosity in an aqueous solution state of a specific concentration, and water. According to the technique described in Patent Document 1, it is said that a lithium-ion secondary battery having excellent cycle life (cycle characteristics) can be obtained by using this negative electrode slurry.

It has also been proposed to use silicon oxide as a negative electrode active material by carbon coating. It is said that the electrical conductivity of silicon oxide particles can be increased by carbon coating, and that the side reaction between silicon oxide and an electrolyte can also be suppressed. Therefore, carbon-coated silicon oxide is expected to be a negative electrode active material for next-generation lithium-ion secondary batteries. For example, Patent Document 2 describes a lithium-ion battery negative electrode slurry containing carbon-coated silicon oxide, graphite having an R value of 0.2 to 1.5, which is the peak intensity ratio at 1360 cm ⁻¹ to the peak intensity at 1580 cm ⁻¹ in an argon ion laser Raman spectrum, a binder, carbon black, and water. According to the technology described in Patent Document 2, it is said that a lithium-ion secondary battery with excellent cycle life can be obtained by doping lithium ions into the negative electrode mixture layer formed using this negative electrode slurry.

Electrodes for lithium-ion secondary batteries are usually formed by applying an electrode-forming composition (slurry) onto a current collector and drying it. Therefore, the slurry for forming the electrode is prepared by dispersing an electrode active material and a binder in a liquid medium. In recent years, with the background of increasing interest in environmental issues, there has been a demand for aqueous liquid media, and various water-soluble binders suitable for aqueous slurries have been developed, for example, as described in the above-mentioned Patent Documents 1 and 2.

JP 2018-6334 A JP 2018-81753 A

The present invention aims to provide a negative electrode composition that uses carbon-coated silicon oxide as a negative electrode active material, which, when used to form a negative electrode active material layer of a non-aqueous secondary battery, can provide a non-aqueous secondary battery with high capacity and low resistance while also sufficiently extending the cycle life. Another object of the present invention is to provide a negative electrode sheet and a non-aqueous secondary battery that use the negative electrode composition. Another object of the present invention is to provide a method for producing the negative electrode sheet and the non-aqueous secondary battery.

In view of the above problems, the present inventors have conducted extensive research into binders to be combined with carbon-coated silicon oxide from the viewpoint of the polymer structure that constitutes the binder. As a result, while the polymer is usually made high molecular weight in consideration of the mechanical strength of the binder, they have found that the above technical problems can be solved to a high level by containing a specific amount or more of a water-soluble polymer in the binder, in which the weight-average molecular weight is restricted to 300,000 or less and the content of components having acid groups that are expected to interact with the active material or between polymers is restricted to a small amount of 5 mass % or less. The present invention was completed after further research based on these findings.

一般式（１）中、Ｒ^１は水素原子又はメチル基を示し、Ｌ^１は単結合又は連結基を示し、Ｒ^２は置換基を示す。＊は上記水溶性ポリマー中に組み込まれるための結合部位を示す。
一般式（２）中、Ｒ^３は水素原子又はメチル基を示し、Ｒ^４及びＲ^５は水素原子又は置換基を示す。＊は上記水溶性ポリマー中に組み込まれるための結合部位を示す。
＜４＞
上記水溶性ポリマーの含有量が、上記のカーボンコートされた酸化ケイ素１００質量部に対して、２質量部以上である、＜１＞～＜３＞のいずれか１つに記載の負極用組成物。
＜５＞
上記水溶性ポリマーが、上記一般式（１）又は（２）で表される２種以上の構成成分を含む、＜３＞に記載の負極用組成物。
＜６＞
上記酸基がカルボキシ基又はその塩である、＜１＞～＜５＞のいずれか１つに記載の負極用組成物。
＜７＞
分散媒体を含む負極用スラリーである、＜１＞～＜６＞のいずれか１つに記載の負極用組成物。
＜８＞
＜１＞～＜７＞のいずれか１つに記載の負極用組成物で構成した層を有する負極シート。
＜９＞
正極活物質層とセパレータと負極活物質層とをこの順で有し、上記負極活物質層が＜１＞～＜７＞のいずれか１つに記載の負極用組成物で構成した層である、非水二次電池。
＜１０＞
＜１＞～＜７＞のいずれか１つに記載の負極用組成物を用いて成膜することを含む、負極シートの製造方法。
＜１１＞
＜１０＞に記載の製造方法により得られた負極シートを非水二次電池の負極に組み込むことを含む、非水二次電池の製造方法。 That is, the above problems were solved by the following means.
＜1＞
A composition for a negative electrode comprising a binder and carbon-coated silicon oxide,
The binder contains a water-soluble polymer in an amount of 5% by mass or more,
the water-soluble polymer has a weight-average molecular weight of 300,000 or less, and the proportion of a component having an acid group in the water-soluble polymer is 5 mass % or less; and
＜2＞
The negative electrode composition according to <1>, wherein the water-soluble polymer is a chain-polymerized polymer.
＜3＞
The negative electrode composition according to <1> or <2>, wherein the water-soluble polymer contains a component represented by the following general formula (1) or (2) as a component having no acid group:

In formula (1), ^R1 represents a hydrogen atom or a methyl group, ^L1 represents a single bond or a linking group, and ^R2 represents a substituent. * represents a bonding site for incorporation into the water-soluble polymer.
In formula (2), ^R3 represents a hydrogen atom or a methyl group, ^R4 and ^R5 represent a hydrogen atom or a substituent, and * represents a bonding site for incorporation into the water-soluble polymer.
＜4＞
<4> The negative electrode composition according to any one of <1> to <3>, wherein the content of the water-soluble polymer is 2 parts by mass or more per 100 parts by mass of the carbon-coated silicon oxide.
＜5＞
The negative electrode composition according to <3>, wherein the water-soluble polymer contains two or more components represented by the general formula (1) or (2).
＜6＞
The negative electrode composition according to any one of <1> to <5>, wherein the acid group is a carboxy group or a salt thereof.
＜７＞
The negative electrode composition according to any one of <1> to <6>, which is a negative electrode slurry containing a dispersion medium.
＜8＞
<8> A negative electrode sheet having a layer constituted by the negative electrode composition according to any one of <1> to <7>.
＜9＞
A non-aqueous secondary battery having a positive electrode active material layer, a separator, and a negative electrode active material layer in this order, the negative electrode active material layer being a layer constituted by the negative electrode composition according to any one of <1> to <7>.
＜10＞
A method for producing a negative electrode sheet, comprising forming a film using the negative electrode composition according to any one of <1> to <7>.
<11>
A method for producing a non-aqueous secondary battery, comprising incorporating the negative electrode sheet obtained by the method for producing the non-aqueous secondary battery into a negative electrode of the non-aqueous secondary battery.

In this specification, the term "water-soluble polymer" refers to a polymer that dissolves at least 7 g in 1 L of water at 25° C. (a polymer whose solubility at 25° C. is 7 [g/1L-H ₂ O] or more).
In this specification, a numerical range expressed using "to" means a range that includes the numerical values before and after "to" as the lower and upper limits.
In this specification, the expression "compound" (for example, when referring to a compound by adding "compound" to the end) refers to the compound itself, as well as its salts and ions. It also refers to derivatives in which a part of the structure has been changed, such as by introducing a substituent, within the scope of the desired effect.
In the present specification, when a substituent has a dissociable hydrogen atom (a group in which the hydrogen atom dissociates due to the action of a base), the substituent includes the form of an ion or a salt.
For example, when a compound has a carboxy group, the carboxy group may be present as an anion with a hydrogen atom dissociated therefrom, and the anion may form a salt with a counter ion (cation). There are no particular limitations on the counter ion, and examples of the counter ion include alkali metal ions such as lithium ion, sodium ion, and potassium ion.
In the present specification, substituents, linking groups, etc. (hereinafter referred to as "substituents, etc.") that are not specified as substituted or unsubstituted are intended to mean that the group may have an appropriate substituent. Thus, even when the term "group" (e.g., "alkyl group") is simply described in the present specification, this "group" (e.g., "alkyl group") includes not only an embodiment that does not have a substituent (e.g., "unsubstituted alkyl group"), but also an embodiment that further has a substituent (e.g., "substituted alkyl group"). This also applies to compounds that are not specified as substituted or unsubstituted.
In this specification, when there are multiple substituents etc. designated by a specific symbol, or when multiple substituents etc. are simultaneously or alternatively specified, it means that the respective substituents etc. may be the same or different from each other. In addition, even if not specified otherwise, when multiple substituents etc. are adjacent, it means that they may be linked to each other or condensed to form a ring.
In this specification, when a polymer has multiple components of the same designation (represented by the same general formula), each component may be the same or different from the others.
In this specification, the term "nonaqueous secondary battery" includes nonaqueous electrolyte secondary batteries and all-solid-state secondary batteries. In this specification, the term "nonaqueous electrolyte" means an electrolyte that does not substantially contain water. That is, the "nonaqueous electrolyte" may contain a small amount of water within a range that does not impede the effects of the present invention. In the present invention, the "nonaqueous electrolyte" has a water concentration of 200 ppm (by mass) or less, preferably 100 ppm or less, and more preferably 20 ppm or less. Note that it is practically difficult to make a nonaqueous electrolyte completely anhydrous, and it usually contains 1 ppm or more of water.
In this specification, the term "solid content" used when describing the content or content ratio means components other than the dispersion medium described below.

The negative electrode composition and negative electrode sheet of the present invention can be used to form a negative electrode active material layer, thereby imparting excellent cycle characteristics to a non-aqueous secondary battery using carbon-coated silicon oxide as a negative electrode active material, and therefore the non-aqueous secondary battery of the present invention has high capacity, low resistance, and excellent cycle characteristics.
According to the method for producing a negative electrode sheet of the present invention, the above-mentioned negative electrode sheet of the present invention can be obtained. Also, according to the method for producing a nonaqueous secondary battery of the present invention, the above-mentioned nonaqueous secondary battery of the present invention can be obtained.

FIG. 1 is a vertical cross-sectional view showing a schematic diagram of a basic layered structure of a nonaqueous electrolyte secondary battery.

[Negative electrode composition]
The negative electrode composition of the present invention contains a binder containing a water-soluble polymer and a negative electrode active material containing carbon-coated silicon oxide.
The water-soluble polymer is a polymer having a weight-average molecular weight of 300,000 or less, and the content of a component having an acid group in the water-soluble polymer is 5% by mass or less. The water-soluble polymer is contained in the binder in an amount of 5% by mass or more.
By incorporating the negative electrode active material layer prepared using the negative electrode composition of the present invention into a secondary battery, the cycle life of the resulting secondary battery can be effectively increased. Although the reason for this is not yet clear, it is presumed that one of the reasons is that the binder contains a certain amount or more of a polymer that has a relatively small molecular weight of 300,000 or less and has a limited amount of acid groups to suppress an increase in apparent molecular weight, and this polymer fits into the voids in the carbon coat layer (producing an anchor effect), thereby firmly binding the water-soluble polymer to the negative electrode active material (carbon-coated silicon oxide).
The negative electrode composition of the present invention can be prepared by mixing a binder containing a water-soluble polymer, a negative electrode active material containing carbon-coated silicon oxide, and, if necessary, a dispersion medium, a conductive assistant, and the like.

(binder)
The binder used in the present invention contains the above-mentioned water-soluble polymer in an amount of 5% by mass or more based on the total amount of the binder.
The water-soluble polymer used in the present invention may be either a chain-polymerized polymer or a step-polymerized polymer, and is preferably a chain-polymerized polymer. The bonding form of the chain-polymerized polymer is not particularly limited, and may be either random or block.

The main component constituting the water-soluble polymer, which does not have an acid group, is not particularly limited. It is preferable that the water-soluble polymer contains, as a component not having an acid group, a component represented by the following general formula (1) or (2).

In formula (1), ^R1 represents a hydrogen atom or a methyl group, ^L1 represents a single bond or a linking group (divalent), and ^R2 represents a substituent. * represents a bonding site for incorporation into a water-soluble polymer.
In formula (2), ^R3 represents a hydrogen atom or a methyl group, ^R4 and ^R5 represent a hydrogen atom or a substituent, and * represents a bonding site for incorporation into a water-soluble polymer.

The linking group that can be taken as ^L1 is not particularly limited as long as it does not have an acid group. The chemical formula weight of this linking group is preferably 14 to 1,000, more preferably 14 to 500, and even more preferably 26 to 250.
Examples of the linking group that can be taken as ^L1 include an alkylene group, -O-, a carbonyl group, an imino group, and a combination thereof. As these combinations, a linking group formed by combining 2 to 6 of the alkylene groups, -O-, carbonyl groups, and imino groups is preferable, and a linking group formed by combining 2 or 3 of them is more preferable.
Specifically, ^L1 is preferably any one of -C(=O)-O-, -O-C(=O)-, -NH-C(=O)-O-, -O-C(=O)-NH-, -NH-C(=O)-NH-, and an alkylene group, and more preferably an alkylene group.
The alkylene group that can be taken as ^L1 may be either linear or branched, and the alkylene group preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, still more preferably 1 to 6 carbon atoms, particularly preferably 1 to 4 carbon atoms, and is most preferably any one of a methylene group, an ethylene group, an ethylethylene group, and a propylene group.
The chemical formula weight of ^L1 is preferably 14-200, more preferably 14-150, and even more preferably 14-80.

^R2 is not particularly limited as long as it is a substituent that does not have an acid group. The chemical formula weight of ^R2 is preferably 15 to 200, more preferably 15 to 150, and even more preferably 15 to 100. Examples of ^R2 include a hydroxy group, an alkyloxy group, an alkyl group, an amide group, and a sulfonamide group, and is preferably a hydroxy group or an alkyloxy group.
The alkyl group in the alkyloxy group may be linear, branched or cyclic, and preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, further preferably 1 to 6 carbon atoms, particularly preferably 1 to 4 carbon atoms, and is most preferably a methyl group, an ethyl group or an isopropyl group.
The alkyl group has the same meaning as the alkyl group in the alkyloxy group, and the preferred range is also the same.

The substituents that can be taken as ^R4 and ^R5 are not particularly limited as long as they are substituents that do not have an acid group. The chemical formula weight of each of ^R4 and ^R5 is preferably 15 to 200, more preferably 15 to 150, and even more preferably 15 to 60. The substituents that can be taken as ^R4 and ^R5 are preferably alkyl groups.
The alkyl group has the same meaning as the alkyl group in the alkyloxy group which can be taken as R ² , and the preferred range is also the same. In addition, it is also preferable that the alkyl group which can be taken as R ⁴ and R ⁵ further has a substituent.
Examples of such a substituent include a hydroxy group, an alkylcarbonyl group, an amide group, and a urethane bond-containing group (-NH-CO-O-R ^b (R ^b represents an alkyl group). Among these, the substituent of the alkyl group which can be taken as R ⁴ and R ⁵ is preferably a hydroxy group.
The alkyl group in the alkylcarbonyl group has the same meaning as the alkyl group in the alkyloxy group which can be taken as the above ^R2 , and the preferred range is also the same. The alkyl group represented by ^Rb has the same meaning as the alkyl group in the alkyloxy group which can be taken as the above ^R2, and the preferred range is also the same.
It is preferable that ^R4 and ^R5 are both hydrogen atoms, or one of them is a hydrogen atom and the other is a hydroxyalkyl group.

The water-soluble polymer used in the present invention may contain one kind of component that does not have an acid group alone, or may contain two or more kinds in combination. The proportion of the component represented by the general formula (1) or (2) in the water-soluble polymer (the sum of the proportion of the component represented by the general formula (1) and the proportion of the component represented by the general formula (2) in the water-soluble polymer) is preferably 30% by mass or more, more preferably 50% by mass or more, even more preferably 70% by mass or more, particularly preferably 90% by mass or more, and most preferably 95% by mass or more.
From the viewpoint of improving the cycle characteristics of the secondary battery, the water-soluble polymer used in the present invention preferably contains two or more components represented by general formula (1) or (2), more preferably contains 2 to 6 components represented by general formula (1) or (2), and even more preferably contains 2 to 4 components represented by general formula (1) or (2). Examples of the form containing two or more components represented by general formula (1) or (2) include a form containing two or more components represented by general formula (1) and no component represented by general formula (2), a form containing two or more components represented by general formula (2) and no component represented by general formula (1), and a form containing both a component represented by general formula (1) and a component represented by general formula (2).

Preferred specific examples of the components represented by the above general formula (1) are shown below, but the present invention is not limited to these forms.

Preferred specific examples of the components represented by the above general formula (2) are shown below, but the present invention is not limited to these forms.

When the water-soluble polymer contains a component other than the component represented by the general formula (1) or (2) as a component not having an acid group, such a component is not particularly limited. For example, a component derived from a vinyl monomer such as styrene, maleimide, N-vinylacetamide, vinyl ester, or vinyl ether can be mentioned.

The "acid group" of the constituent having an acid group that the water-soluble polymer may have refers to a group having a dissociable proton or a salt thereof. Examples include a carboxy group, a sulfo group, a phosphate group (-OP(=O)(OH) ₂ ), a phosphonic acid group (-P(=O)(OH) ₂ ), or a salt thereof, with a carboxy group and a sulfo group or a salt thereof being preferred, and a carboxy group or a salt thereof being more preferred. Examples of the salt form include alkali metal salts (e.g., lithium salts, sodium salts, potassium salts, etc.).

The component having an acid group is not particularly limited, and this component usually contains 1 to 3 acid groups, preferably 1 or 2, and more preferably 1. When the water-soluble polymer contains a component having an acid group, it is preferable that the water-soluble polymer contains, for example, a component represented by the following general formula (3).

In the formula, ^R6 represents a hydrogen atom or an acid group, ^R7 represents a hydrogen atom or a methyl group, ^L2 represents a single bond or a linking group (divalent), and ^R8 represents an acid group. * represents a bonding site for incorporation into a water-soluble polymer.

The linking group that can be taken as ^L2 is not particularly limited, and examples thereof include an alkylene group, an arylene group, a carbonyl group, an ether bond (-O-) or an imino group, or a linking group that is a combination of two or more of these.

The alkylene group that can be taken as ^L2 may be either linear or branched, and the alkylene group preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, still more preferably 1 to 6 carbon atoms, particularly preferably 1 to 4 carbon atoms, and is most preferably any one of a methylene group, an ethylene group, a propylene group, and a dimethylethylene group.

The number of carbon atoms in the arylene group which can be taken as ^L2 is preferably 6 to 30, more preferably 6 to 20, still more preferably 6 to 15, and particularly preferably 6 to 10. Specific examples of the arylene group include a phenylene group and a naphthylene group.

The above-mentioned "linking group combining two or more types" is a linking group combining at least two types of an alkylene group, an arylene group, a carbonyl group, an ether bond (-O-), and an imino group, and is preferably a linking group combining 2 to 10 types, more preferably a linking group combining 2 to 7 types, and even more preferably a linking group combining 2 to 4 types.
Specific examples of the above-mentioned "linking group combining two or more types" include "carbonyl group-imino group-alkylene group" and "carbonyl group-ether bond-alkylene group".

The proportion of components having acid groups in the water-soluble polymer is 5% by mass or less, preferably 4% by mass or less, more preferably 3% by mass or less, even more preferably 2% by mass or less, and particularly preferably 1% by mass or less, and it is most preferable that the water-soluble polymer does not have any components having acid groups.

Preferred specific examples of the components represented by the above general formula (3) are shown below, but the present invention is not limited to these forms.

The weight-average molecular weight of the water-soluble polymer used in the present invention is 300,000 or less, preferably 290,000 or less, more preferably 280,000 or less, and even more preferably 270,000 or less. On the other hand, the weight-average molecular weight of the water-soluble polymer is preferably 10,000 or more, more preferably 40,000 or more, even more preferably 100,000 or more, particularly preferably 140,000 or more, and most preferably 170,000 or more.
In this specification, the weight average molecular weight of a polymer is a value obtained by measurement according to the method described in the Examples section below.

In the binder used in the present invention, the content of the water-soluble polymer is 5% by mass or more, and from the viewpoint of improving the cycle characteristics of the secondary battery, the content is preferably 10% by mass or more, and more preferably 20% by mass or more. The binder used in the present invention may be made of the water-soluble polymer.

From the viewpoint of improving the cycle characteristics of the secondary battery, the content of the water-soluble polymer in the negative electrode composition is preferably 2 parts by mass or more, more preferably 4 parts by mass or more, and even more preferably 8 parts by mass or more, per 100 parts by mass of the carbon-coated silicon oxide. On the other hand, the content of the water-soluble polymer in the negative electrode composition is preferably 30 parts by mass or less, more preferably 25 parts by mass or less, and even more preferably 20 parts by mass or less, per 100 parts by mass of the carbon-coated silicon oxide.

The binder used in the present invention may contain a polymer other than the water-soluble polymer. Examples of such polymers include water-insoluble polymers, water-soluble polymers having a weight-average molecular weight of more than 300,000, and water-soluble polymers having a content of components having an acid group of more than 5% by mass. A specific example of such a polymer is polymer B described in Table 1 below, but polymer B is not limited to "polymer B described in Table 1 below."

(Negative Electrode Active Material)
The negative electrode active material used in the present invention includes carbon-coated silicon oxide (SiOx (0<x≦1.5)). Carbon-coated silicon oxide can reversibly absorb and release lithium ions.
The silicon oxide may have a carbon-coated surface in its entirety, or may have a portion that is not carbon-coated. Even if the silicon oxide has a carbon-coated surface in its entirety, the carbon-coated layer itself has a large number of voids.
The proportion of carbon atoms in the carbon-coated silicon oxide (the total of the carbon coating layer and silicon oxide) is not particularly limited, and is, for example, preferably 0.5 to 5 mass %, more preferably 1 to 3 mass %.
Carbon-coated silicon oxide may be a commercially available product, or it can be prepared by carbon-coating silicon oxide with reference to, for example, JP-A-2019-204686.

The negative electrode active material used in the present invention may contain a negative electrode active material other than carbon-coated silicon oxide. In the following description of the negative electrode active material used in the present invention, the negative electrode active material other than carbon-coated silicon oxide is referred to as "other negative electrode active material."
The other negative electrode active material is preferably one that can reversibly absorb and release lithium ions. The material is not particularly limited as long as it has the above-mentioned characteristics, and examples of the material include carbonaceous materials, metal oxides, metal composite oxides, lithium alloys, and negative electrode active materials that can form alloys with lithium.
The lithium alloy is not particularly limited as long as it is an alloy that is usually used as a negative electrode active material for secondary batteries, and an example thereof is a lithium aluminum alloy.
The negative electrode active material capable of forming an alloy with lithium is not particularly limited as long as it is a material that is commonly used as a negative electrode active material for secondary batteries. Examples of such active materials include negative electrode active materials having tin atoms, and metals such as Al and In.
Examples of the negative electrode active material having tin atoms include Sn, SnO, _SnO2 , SnS, _SnS2 , and the above-mentioned active materials containing silicon atoms and tin _atoms . Also included are composite oxides with lithium oxide, such as _Li2SnO2 .
Among these, as the other negative electrode active material, carbonaceous materials are preferably used from the viewpoint of reliability.

Other carbonaceous materials used as negative electrode active materials are materials that are essentially made of carbon. Examples include carbon black such as petroleum pitch, graphite (natural graphite, artificial graphite such as vapor-grown graphite, etc.), and carbonaceous materials obtained by baking various synthetic resins such as PAN (polyacrylonitrile)-based resins or furfuryl alcohol resins. In addition, various carbon fibers such as PAN-based carbon fibers, cellulose-based carbon fibers, pitch-based carbon fibers, vapor-grown carbon fibers, dehydrated PVA (polyvinyl alcohol)-based carbon fibers, lignin carbon fibers, glassy carbon fibers, and activated carbon fibers, mesophase microspheres, graphite whiskers, and plate-shaped graphite can also be mentioned.

Other metal oxides and metal composite oxides that can be used as negative electrode active materials are not particularly limited as long as they are oxides that can absorb and release lithium, and amorphous oxides are preferred, and chalcogenides that are reaction products of metal elements and elements of group 16 of the periodic table are also preferred. The term "amorphous" as used herein means that the oxide has a broad scattering band with a peak in the 2θ value range of 20° to 40° in an X-ray diffraction method using CuKα radiation, and may have crystalline diffraction lines.
Among the compound group consisting of the above-mentioned amorphous oxides and chalcogenides, amorphous oxides of metalloid elements and the above-mentioned chalcogenides are more preferred, and oxides consisting of one kind alone or a combination of two or more kinds of elements of Groups 13 (IIIB) to 15 (VB) of the periodic table, Al, Ga, Si, Sn, Ge, Pb, Sb, and Bi (however, oxides containing Si are excluded), or chalcogenides are particularly preferred. Specific examples of preferred amorphous oxides and chalcogenides include _Ga2O3 , _GeO , _PbO , _PbO2 , _Pb2O3 , Pb2O4, _{Pb3O4 , Sb2O3 , Sb2O4 , Sb2O8Bi2O3 , Sb2O5 , Bi2O3 , Bi2O4 , GeS} , _{PbS , PbS2 , Sb2S3 and Sb2S5 .}

The metal (composite) oxide and the chalcogenide preferably contain at least one of titanium and lithium as a component from the viewpoint of high current density charge/discharge characteristics. Examples of the metal composite oxide containing lithium (lithium composite metal oxide) include composite oxides of lithium oxide and the metal (composite) oxide or the chalcogenide, more specifically Li ₂ SnO ₂ .

Other negative electrode active materials are also preferably those containing titanium atoms. More specifically, TiNb ₂ O ₇ (niobium titanate oxide [NTO]) and Li ₄ Ti ₅ O ₁₂ (lithium titanate [LTO]) are preferred because they have small volume fluctuations during the absorption and release of lithium ions, and therefore have excellent rapid charge and discharge characteristics, suppress electrode deterioration, and enable an improvement in the life of the lithium ion secondary battery.

The shape of the carbon-coated silicon oxide and other negative electrode active materials is not particularly limited, but particulate is preferred. The volume-based median diameter D50 of the carbon-coated silicon oxide and other negative electrode active materials is preferably 0.1 to 60 μm. To obtain a desired particle size, a conventional grinder or classifier is used. For example, a mortar, a ball mill, a sand mill, a vibration ball mill, a satellite ball mill, a planetary ball mill, a swirling airflow type jet mill, or a sieve is preferably used. During grinding, wet grinding in the presence of water or an organic solvent such as methanol can also be performed. In order to obtain a desired particle size, it is preferable to perform classification. The classification method is not particularly limited, and a sieve, a wind classifier, etc. can be used as desired. Classification can be performed both dry and wet.

The median diameter D50 of the carbon-coated silicon oxide is preferably from 0.1 to 30 μm, more preferably from 0.5 to 20 μm, and particularly preferably from 2 to 8 μm.
The median diameter D50 can be determined by a laser diffraction method, for example, using SALD-2300 (product name) manufactured by Shimadzu Corporation.

When carbon-coated silicon oxide is used in combination with other negative electrode active materials, a combination of carbon-coated silicon oxide and a carbonaceous material is preferred, and a combination of carbon-coated silicon oxide and graphite is particularly preferred. When carbon-coated silicon oxide and graphite are combined, the mass ratio (carbon-coated silicon oxide/graphite) is preferably 0.1 or more, more preferably 0.2 or more, and even more preferably 0.3 or more. There is no particular upper limit to the mass ratio of carbon-coated silicon oxide to graphite, but 4 or less is practical.
The content of the carbon-coated silicon oxide in the negative electrode active material is not particularly limited and can be, for example, 10 to 90 mass %, preferably 10 to 50 mass %, and more preferably 15 to 40 mass %.
When forming the negative electrode active material layer, the mass (mg) (weight per unit area) of the carbon-coated silicon oxide and other negative electrode active materials per unit area (cm ² ) of the negative electrode active material layer is not particularly limited and can be appropriately determined depending on the designed battery capacity.

The content of carbon-coated silicon oxide and other negative electrode active materials in the negative electrode composition is not particularly limited, but is preferably 10 to 98 mass% in total, and more preferably 15 to 95 mass%, based on 100 mass% solids.

(Dispersion Medium)
The negative electrode composition of the present invention can also contain a dispersion medium to form a negative electrode slurry.
When a non-aqueous electrolyte secondary battery is produced using the negative electrode composition of the present invention, an aqueous medium containing water can be used as the dispersion medium. The "aqueous medium containing water" refers to water or a mixture of water and a water-soluble organic solvent. The "water-soluble organic solvent" refers to an organic solvent that does not undergo phase separation when mixed with water, and examples of such an organic solvent include N-methylpyrrolidone, methanol, ethanol, acetone, and tetrahydrofuran.

(Conductive assistant)
The negative electrode composition of the present invention may also contain a conductive assistant.
The conductive assistant is not particularly limited, and may be any known conductive assistant. For example, it may be an electron conductive material such as graphites such as natural graphite and artificial graphite, carbon blacks such as acetylene black, ketjen black, and furnace black, amorphous carbon such as needle coke, carbon fibers such as vapor-grown carbon fibers or carbon nanotubes, carbonaceous materials such as graphene or fullerene, metal powders or metal fibers such as copper and nickel, or conductive polymers such as polyaniline, polypyrrole, polythiophene, polyacetylene, and polyphenylene derivatives.
In the present invention, when a negative electrode active material and a conductive assistant are used in combination, among the above conductive assistants, those that do not insert or release Li when the secondary battery is charged and discharged and do not function as a negative electrode active material are considered to be conductive assistants. Therefore, among the conductive assistants, those that can function as a negative electrode active material in the negative electrode active material layer when the secondary battery is charged and discharged are classified as negative electrode active materials rather than conductive assistants. Whether or not a conductive assistant functions as a negative electrode active material when the secondary battery is charged and discharged is not unique, but is determined by the combination with the negative electrode active material.

The conductive assistant may be used alone or in combination of two or more.
The content of the conductive assistant in the negative electrode composition is preferably 10 to 90 mass %, more preferably 30 to 80 mass %, and even more preferably 50 to 70 mass %, based on 100 mass % of the solid content.

The shape of the conductive additive is not particularly limited, but particulate is preferred. The median diameter D50 of the conductive additive is not particularly limited, but is preferably 0.01 to 50 μm, and more preferably 0.02 to 10.0 μm.

(Other Additives)
The negative electrode composition of the present invention may contain, as desired, other components in addition to the above-mentioned components, such as a lithium salt, an ionic liquid, a thickener, an antifoaming agent, a leveling agent, a dehydrating agent, an antioxidant, etc. In addition, the composition may contain a crosslinking agent (such as one that undergoes a crosslinking reaction by radical polymerization, condensation polymerization, or ring-opening polymerization) for chemically crosslinking the water-soluble polymer, and further a polymerization initiator (such as one that generates an acid or radicals by heat or light).
With regard to the conductive assistant and other additives, for example, International Publication No. 2019/203334 and JP-A-2015-46389 can be referred to.

[Negative electrode sheet]
The negative electrode sheet of the present invention has a layer (negative electrode active material layer) that is constructed (formed) using the negative electrode composition of the present invention. The negative electrode sheet of the present invention may have a negative electrode active material layer, and may be a sheet in which the negative electrode active material layer is formed on a substrate (current collector), or may be a sheet formed only of the negative electrode active material layer without a substrate. This negative electrode sheet is usually a sheet having a configuration in which the negative electrode active material layer is laminated on the current collector. The negative electrode sheet of the present invention may have other layers such as a protective layer (release sheet) and a coating layer.
The negative electrode sheet of the present invention can be suitably used as a material constituting the negative electrode active material layer of a secondary battery.

[Method of manufacturing negative electrode sheet]
The negative electrode sheet of the present invention can be obtained by forming a negative electrode active material layer using the negative electrode composition of the present invention. For example, a current collector or the like is used as a substrate, and the negative electrode composition of the present invention is applied thereon (with or without another layer) to form a coating film, which is then dried to obtain an electrode sheet having a negative electrode active material layer (coated and dried layer) on the substrate.

[Non-aqueous secondary battery]
The nonaqueous secondary battery of the present invention refers to any device in which ions pass between positive and negative electrodes via an electrolyte upon charging and discharging, and energy is stored and released at the positive and negative electrodes. That is, the nonaqueous secondary battery of the present invention includes both batteries and capacitors (e.g., lithium ion capacitors). From the viewpoint of the amount of energy stored, it is preferable that the nonaqueous secondary battery of the present invention is used for battery applications (not as a capacitor).

The nonaqueous secondary battery of the present invention will be described taking a nonaqueous electrolyte secondary battery as an example, but the secondary battery of the present invention is not limited to a nonaqueous electrolyte secondary battery and broadly includes all nonaqueous secondary batteries including all-solid-state secondary batteries.
A nonaqueous electrolyte secondary battery according to a preferred embodiment of the present invention includes a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode. The positive electrode includes a positive electrode current collector and a positive electrode active material layer in contact with the positive electrode current collector, and the negative electrode includes a negative electrode current collector and a negative electrode active material layer in contact with the negative electrode current collector. In the nonaqueous electrolyte secondary battery of the present invention, the negative electrode active material layer is formed using the electrode composition of the present invention.

FIG. 1 is a cross-sectional view showing a typical laminated structure of a nonaqueous electrolyte secondary battery 10, including a working electrode when the battery is operated. The nonaqueous electrolyte secondary battery 10 has a laminated structure having, in this order, a negative electrode current collector 1, a negative electrode active material layer 2, a separator 3, a positive electrode active material layer 4, and a positive electrode current collector 5, as seen from the negative electrode side. The space between the negative electrode active material layer and the positive electrode active material layer is filled with a nonaqueous electrolyte (not shown), and is separated by the separator 3. The separator 3 has pores, and in a normal battery use state, it functions as a positive and negative electrode separator that insulates between the positive and negative electrodes while allowing the electrolyte and ions to pass through. With this structure, for example, in the case of a lithium ion secondary battery, electrons (e ⁻ ) are supplied to the negative electrode side through an external circuit during charging, and at the same time, lithium ions (Li ⁺ ) move from the positive electrode through the electrolyte and are accumulated in the negative electrode. On the other hand, during discharging, the lithium ions (Li ⁺ ) stored in the negative electrode are returned to the positive electrode side via the electrolyte, and electrons are supplied to the operating part 6. In the illustrated example, a light bulb is used as the operating part 6, and this is turned on by discharging.
In the present invention, the negative electrode current collector 1 and the negative electrode active material layer 2 are collectively referred to as the negative electrode, and the positive electrode active material layer 4 and the positive electrode current collector 5 are collectively referred to as the positive electrode.

The nonaqueous secondary battery of the present invention is not particularly limited in terms of the positive electrode active material material, nonaqueous electrolyte, solid electrolyte material, and other components, except that the negative electrode active material layer is formed using the negative electrode composition of the present invention. These materials and components can be appropriately applied to those used in normal nonaqueous secondary batteries. In addition, for the method of producing the nonaqueous secondary battery of the present invention, a normal method can be appropriately adopted, except that the negative electrode active material layer is formed using the negative electrode composition of the present invention. For example, JP 2016-201308 A, JP 2005-108835 A, JP 2012-185938 A, and WO 2020/067106 A can be appropriately referred to.

The nonaqueous secondary battery of the present invention can be mounted in electronic devices such as notebook computers, pen-input computers, mobile computers, electronic book players, mobile phones, cordless phone handsets, pagers, handheld terminals, portable fax machines, portable copiers, portable printers, headphone stereos, video movie machines, liquid crystal televisions, handheld cleaners, portable CDs, mini-discs, electric shavers, transceivers, electronic organizers, calculators, portable tape recorders, radios, backup power sources, and memory cards. It can also be mounted in consumer devices such as automobiles, electric vehicles, motors, lighting equipment, toys, game equipment, road conditioners, watches, strobes, cameras, and medical equipment (pacemakers, hearing aids, shoulder massagers, etc.). It can also be combined with solar cells.

The present invention will be described in more detail with reference to examples. Note that the present invention is not to be construed as being limited by these examples except as provided for in the present invention.

[Synthesis of Polymer A]
<Synthesis of Polymer 1 (Polymer No. 1 in Table 1 below)>
Polymer 1 shown in Table 1 below was synthesized as follows.
A 500 mL separable flask was charged with 108.1 g of ion-exchanged water, and a mixed solution containing 17.5 g of 2-hydroxyethyl acrylate, 52.5 g of N-(2-hydroxyethyl)acrylamide, and 24.9 g of ion-exchanged water, and a mixed solution containing 1.26 g of 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] tetrahydrate and 33.3 g of ion-exchanged water were simultaneously added dropwise over one hour while stirring at 75°C under a nitrogen atmosphere. After completion of the dropwise addition, the mixture was stirred at 75°C for two hours to obtain a polymer solution with a solid content of 29.8% by mass.

<Synthesis of polymers 2 to 19 and c1 to c3 (synthesis of polymers No. 2 to 19 and c1 to c3 in Table 1 below)
Polymers 2 to 19 and c1 to c3 were synthesized in the same manner as in the synthesis of Polymer 1, except that the monomers shown in Table 1 below were used in the mass ratios shown in Table 1 below as monomers from which the constituent components were derived.

(Measurement of weight average molecular weight)
The weight average molecular weight (Mw) of the polymer shown in Table 1 below is a weight average molecular weight calculated as sodium polyacrylate by gel permeation chromatography (GPC), and is a value measured under the following conditions.
Measuring instrument: HLC-8220GPC (product name, manufactured by Tosoh Corporation)
Columns: TOSOH TSKgel 5000PWXL (product name, manufactured by Tosoh Corporation), TOSOH TSKgel G4000PWXL (product name, manufactured by Tosoh Corporation), and TOSOH TSKgel G2500PWXL (product name, manufactured by Tosoh Corporation) were connected.
Guard column: TSKgel guard column PWXL (product name, manufactured by Tosoh Corporation)
Carrier: 200 mM sodium nitrate aqueous solution Rinse solution: ultrapure water Carrier flow rate: Sample pump 1.0 mL/min
Reference pump 0.223mL/min
Initial pump pressure: Sample pump 4.4MPa
Reference pump 0.8MPa
Sample concentration: 0.10% by mass
Column temperature: 40°C
Detector temperature: 40°C
Collection time: 45 minutes (runtime 47.0 minutes)
Detector: RI (refractive index) detector

[Preparation of negative electrode composition 1 (composition No. 1 in Table 1 below)]
A 60 ml ointment container (Umano Chemical Co., Ltd.) was charged with 30 parts by mass of carbon-coated silicon oxide (SiOC, carbon atom content ratio 1.3 mass%, average primary particle size: 5 μm, Osaka Titanium Co., Ltd.), 70 parts by mass of graphite (trade name: mag-d, Hitachi Chemical Co., Ltd.), 5 parts by mass of acetylene black (trade name: Denka Black, Denka Co., Ltd.), 5 parts by mass of polymer 1, and 22.5 parts by mass of distilled water, and dispersed for 10 minutes at 2000 rpm using a foaming mixer (trade name, THINKY Co., Ltd.). 27 parts by mass of distilled water was added to the dispersed liquid, and dispersed for 10 minutes at 2000 rpm using a foaming mixer, to obtain a negative electrode composition 1.

[Preparation of negative electrode compositions 2 to 19 and c1 to c3 (compositions No. 2 to 19 and c1 to c3 in Table 1 below)]
Negative electrode compositions 2 to 19 and c1 to c3 were prepared in the same manner as in the preparation of the negative electrode composition 1, except that polymers 2 to 19 and c1 to c3 shown in Table 1 below were used instead of polymer 1.

[Preparation of Non-aqueous Electrolyte Secondary Battery (2032 Type Coin Battery) 1 (Battery No. 1 in Table 1 below)]
The obtained negative electrode composition 1 was applied onto a copper foil having a thickness of 20 μm using an applicator and dried for 1 hour at 80° C. Thereafter, the composition was pressed using a press machine and then dried in a vacuum at 150° C. for 6 hours to obtain a negative electrode sheet having a negative electrode active material layer having a thickness of 25 μm.
A disk having a diameter of 13.0 mm was cut out from the negative electrode sheet and used to form a negative electrode.
Lithium foil (thickness 50 μm, 14.5 mmφ) and a polypropylene separator (thickness 25 μm, 16.0 mmφ) were stacked in this order, and 200 μL of 1M LiPF ₆ ethylene carbonate/ethyl methyl carbonate (volume ratio 1:2) electrolyte was impregnated into the separator. 200 μL of electrolyte was further impregnated into the separator, and the negative electrode sheet was stacked so that the negative electrode active material layer surface was in contact with the separator. Then, a 2032-type coin case was crimped to prepare a nonaqueous electrolyte secondary battery 1 (a battery having a laminate consisting of Li foil-separator-negative electrode active material layer-copper foil).

[Preparation of Nonaqueous Electrolyte Secondary Batteries 2 to 19 and c1 to c3 (Batteries No. 2 to 19 and c1 to c3 in Table 1 below)]
Non-aqueous electrolyte secondary batteries 2 to 19 and c1 to c3 were produced in the same manner as in the production of the non-aqueous electrolyte secondary battery 1, except that negative electrode compositions 2 to 19 and c1 to c3 shown in Table 1 below were used instead of the negative electrode composition 1.

[Test Example] Evaluation of cycle characteristics The discharge capacity retention rate of each coin battery was measured using a charge/discharge evaluation device: TOSCAT-3000 (product name, manufactured by Toyo Systems Co., Ltd.). Charging was performed at a C rate of 0.2C (a rate at which the battery is fully charged in 5 hours) until the battery voltage reached 0.02V. Discharging was performed at a C rate of 0.2C until the battery voltage reached 1.5V. Each coin battery was initialized by repeating three cycles of charging and discharging, with one charge and one discharge constituting one charge/discharge cycle.
After the initialization, charging was performed at 0.5 C until the voltage reached 0.02 V. Discharging was performed at 0.5 C until the voltage reached 1.5 V. This one charge and one discharge constituted one charge/discharge cycle, and 50 charge/discharge cycles were repeated to evaluate the cycle characteristics. When the discharge capacity at the first cycle after initialization (initial discharge capacity) was taken as 100%, the discharge capacity maintenance rate at the 50th cycle (100 x "discharge capacity at the 50th cycle"/"initial discharge capacity") was calculated, and the cycle characteristics were evaluated according to the following evaluation ranks. The results are shown in Table 1 below. In this test, evaluation ranks "1" to "3" are pass.
-Evaluation rank of discharge capacity retention rate (cycle characteristics)-
1: 95% or more 2: 90% or more, but less than 95% 3: 85% or more, but less than 90% 4: Less than 85%

Notes for the table:
The abbreviations of the monomers from which the components are derived are explained. Also, the structures of the components derived from the monomers are described.
(Components not having an acid group)
HEA: 2-hydroxyethyl acrylate HEAA: N-(2-hydroxyethyl)acrylamide Aam: acrylamide MEA: 2-methoxyethyl acrylate

(Component having an acid group)
AA: Sodium acrylate AMPS: 2-acrylamido-2-methylpropanesulfonic acid

Latex: copolymer latex of styrene/2-ethylhexyl acrylate/acrylic acid=40/55/5 (mass ratio), Mw=1.2 million, average primary particle size 3 μm (solid content 15 mass %), this latex is water-insoluble.
Water-soluble high acid group polymer: a random copolymer synthesized in the same manner as polymer 1 above ("HEAA/HEA/AA", HEAA:HEA:AA = 70:20:10 (mass ratio), Mw = 150,000)
Water-soluble high molecular weight polymer: a random copolymer synthesized in the same manner as polymer 1 above ("HEAA/HEA", HEAA:HEA = 50:50 (mass ratio), Mw = 400,000)

"Acid group content (mass %) in polymer A" means the content of components having an acid group in polymer A.
"Content 1 (parts by mass)": when the content of SiOC in the negative electrode composition is taken as 100 parts by mass, this refers to the content of polymer A relative to 100 parts by mass of SiOC.
"Content in binder (% by mass)" means the content of the water-soluble polymer defined in the present invention in the binder.
"Content 2 (parts by mass)": means the content of polymer B relative to 100 parts by mass of SiOC in the negative electrode composition, where the content of SiOC is 100 parts by mass. The content of "latex" is the content of solids.
All of the polymers A, including the comparative examples, are water-soluble.

The polymer A used in the negative electrode compositions No. c1 and c3 has a content of a component having an acid group exceeding 5 mass %. The batteries No. c1 and c3 fabricated using the negative electrode compositions No. c1 and c3 had poor cycle characteristics.
The polymer A used in the negative electrode composition of No. c2 has a content of a component having an acid group of 5 mass% or less, but has a weight average molecular weight of more than 300,000. The battery No. c2 produced using the negative electrode composition of No. c2 had poor cycle characteristics.
In contrast, it is clear that the batteries (Nos. 1 to 19) produced using the negative electrode compositions of the present invention (Nos. 1 to 19) have excellent cycle characteristics.

Although the present invention has been described in conjunction with its embodiments, we do not intend to limit our invention to any of the details of the description unless specifically stated otherwise, and believe that the appended claims should be interpreted broadly without departing from the spirit and scope of the invention as set forth in the appended claims.

This application claims priority to Patent Application No. 2021-060333, filed in Japan on March 31, 2021, the contents of which are incorporated herein by reference as part of the present specification.

Reference Signs List 10: nonaqueous electrolyte secondary battery 1: negative electrode current collector 2: negative electrode active material layer 3: separator 4: positive electrode active material layer 5: positive electrode current collector 6: operating part (light bulb)

Claims (9)

A composition for a negative electrode comprising a binder and carbon-coated silicon oxide,
The binder contains 5% by mass or more of a water-soluble polymer which is a chain-polymerized polymer ,
the water-soluble polymer has a weight average molecular weight of 300,000 or less, and a ratio of a component having an acid group in the water-soluble polymer is 5 mass% or less,
The negative electrode composition , wherein the water-soluble polymer contains a component represented by the following general formula (1) or (2) as a component having no acid group :

In formula (1), R1 ^represents a hydrogen atom or a methyl group, L1 ^represents a single bond or a linking group, and R2 ^represents a substituent. * represents a bonding site for incorporation into the water-soluble polymer.
In formula (2), R3 ^represents a hydrogen atom or a methyl group, R4 ^and R5 ^represent a hydrogen atom or a substituent, and * represents a bonding site for incorporation into the water-soluble polymer. 2. The negative electrode composition according to claim 1 , wherein the content of the water-soluble polymer is 2 parts by mass or more per 100 parts by mass of the carbon-coated silicon oxide. The negative electrode composition according to claim 1 or 2 , wherein the water-soluble polymer contains two or more components represented by the general formula (1) or (2). 4. The negative electrode composition according to claim 1, wherein the acid group is a carboxy group or a salt thereof. The negative electrode composition according to any one of claims 1 to 4 , which is a negative electrode slurry containing a dispersion medium. A negative electrode sheet having a layer constituted of the negative electrode composition according to any one of claims 1 to 5 . A non-aqueous secondary battery comprising a positive electrode active material layer, a separator, and a negative electrode active material layer in this order, the negative electrode active material layer being a layer constituted by the negative electrode composition according to any one of claims 1 to 5 . A method for producing a negative electrode sheet, comprising forming a film using the negative electrode composition according to any one of claims 1 to 5 . A method for producing a non-aqueous secondary battery, comprising incorporating the negative electrode sheet obtained by the method according to claim 8 into a negative electrode of the non-aqueous secondary battery.

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