WO2022210739A1

WO2022210739A1 - Composition for negative electrode, negative electrode sheet, non-aqueous secondary battery, and methods respectively for producing negative electrode sheet and non-aqueous secondary battery

Info

Publication number: WO2022210739A1
Application number: PCT/JP2022/015557
Authority: WO
Inventors: 祥平片岡; 郁雄木下; 景河野; 一樹瀧本
Original assignee: 富士フイルム株式会社; 富士フイルム和光純薬株式会社
Priority date: 2021-03-31
Filing date: 2022-03-29
Publication date: 2022-10-06
Also published as: JPWO2022210739A1

Abstract

A composition for a negative electrode, which comprises a binder comprising a water-soluble polymer and carbon-coated silicon oxide, in which the water-soluble polymer has a ratio of adsorption of the carbon-coated silicon oxide of 5 to 25%; a negative electrode sheet and a non-aqueous secondary battery, each of which is produced using the composition for a negative electrode; and a method for producing the negative electrode sheet and a method for producing the non-aqueous secondary battery.

Description

Negative electrode composition, negative electrode sheet, non-aqueous secondary battery, and method for producing negative electrode sheet and non-aqueous secondary battery

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, typified by lithium-ion secondary batteries, are used as power sources for portable electronic devices such as personal computers, video cameras, and mobile phones. Recently, against the background of the global environmental issue of reducing carbon dioxide emissions, it is becoming popular as a power source for transportation equipment such as automobiles, and as a power storage application such as nighttime power and power generated by natural energy generation.

The electrodes (positive electrode and negative electrode) of the lithium ion secondary battery have an electrode active material layer (positive electrode active material layer and negative electrode active material layer), and this electrode active material layer can absorb or release lithium ions during charging and discharging. Contains electrode active material particles. In addition, since electrons are also transported between the electrode active material particles or between the electrode active material particles and the current collector, it is required to ensure electron conductivity. The binding between the electrode active material particles or between the electrode active material particles and the current collector is important for the efficiency of this electron conduction, and the electrode active material layer usually contains a binder.

In order to increase the capacity of lithium-ion secondary batteries, studies have been conducted to use silicon oxide as a negative electrode active material. The theoretical capacity of silicon oxide is remarkably higher than that of graphite and the like, making it possible to increase the energy density of batteries.
When silicon oxide is used as the negative electrode active material, it absorbs a large amount of lithium ions and expands greatly during charging, and the amount of shrinkage of silicon oxide during discharging is correspondingly increased. Therefore, in a lithium-ion battery using silicon oxide as a negative electrode active material, the negative electrode active material undergoes a large volume change during charging and discharging, and the battery performance tends to deteriorate due to repeated charging and discharging. In other words, there are restrictions on improving the cycle life.
As a technique for dealing with such problems, for example, Patent Document 1 discloses a negative electrode active material containing 20% by mass or more of silicon particles having a median diameter (D50) of 0.1 to 2 μm, and a (meth)acrylamide skeleton-containing monomer. and a sulfonic acid group-substituted unsaturated hydrocarbon group-containing monomer, which is a radical copolymer of a monomer group and exhibits a specific high viscosity in an aqueous solution of a specific concentration, and a lithium ion containing poly(meth)acrylamide and water. Slurries for battery anodes are described. According to the technique described in the patent document, it is said that a lithium ion secondary battery having excellent cycle life (cycle characteristics) can be obtained using this negative electrode slurry.

It has also been proposed to coat silicon oxide with carbon and use it as a negative electrode active material. It is said that the carbon coating can increase the conductivity of the silicon oxide particles and suppress the side reaction between the silicon oxide and the electrolyte. Therefore, carbon-coated silicon oxide is expected as a negative electrode active material for next-generation lithium-ion secondary batteries. For example, in Patent Document 2, carbon-coated silicon oxide and graphite having an R value, which is the ratio of the peak intensity at 1360 cm ⁻¹ to the peak intensity at 1580 cm ⁻¹ in the argon ion laser Raman spectrum, is 0.2 to 1.5. , a binder, carbon black, and water for a lithium ion battery negative electrode. According to the description in the patent document, a lithium ion secondary battery having excellent cycle life can be obtained by doping lithium ions into a 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, a slurry for electrode formation is prepared by dispersing an electrode active material and a binder in a liquid medium. Against the backdrop of recent heightened interest in environmental problems, there is a growing demand for water-based liquid media.

JP 2018-6334 A JP 2018-81753 A

The present invention relates to a negative electrode composition using carbon-coated silicon oxide as a negative electrode active material, which is used to form a negative electrode active material layer of a nonaqueous secondary battery. An object of the present invention is to provide a negative electrode composition capable of sufficiently extending the cycle life while achieving high capacity and low resistance. A further object of the present invention is to provide a negative electrode sheet and a non-aqueous secondary battery using the negative electrode composition. A further object of the present invention is to provide a method for manufacturing the negative electrode sheet and the non-aqueous secondary battery.

The above problems have been solved by the following means.
<1>
Containing a binder containing a water-soluble polymer and carbon-coated silicon oxide,
A composition for a negative electrode, wherein the water-soluble polymer has an adsorption rate of 5 to 25% with respect to the carbon-coated silicon oxide.
<2>
The negative electrode composition according to <1>, wherein the water-soluble polymer is a chain 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).

In general formula (1), R ¹ represents a hydrogen atom or a methyl group, L ¹ represents a single bond or a linking group, and R ² represents a substituent. * indicates a binding site for incorporation into the water-soluble polymer.
^In general formula ( ² ), R3 represents a hydrogen atom or a methyl group, and ^R4 and R5 represent a hydrogen atom or a substituent. * indicates a binding site for incorporation into the water-soluble polymer.
<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 with respect to 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 constituents represented by the general formula (1) or (2).
<6>
The negative electrode composition according to any one of <1> to <5>, which is a negative electrode slurry containing a dispersion medium.
<7>
A negative electrode sheet having a layer formed using the negative electrode composition according to any one of <1> to <6>.
<8>
A layer having a positive electrode active material layer, a separator, and a negative electrode active material layer in this order, wherein the negative electrode active material layer is formed using the negative electrode composition according to any one of <1> to <6>. A non-aqueous secondary battery.
<9>
A method for producing a negative electrode sheet, comprising forming a film using the negative electrode composition according to any one of <1> to <6>.
<10>
A method for producing a non-aqueous secondary battery, comprising incorporating the negative electrode sheet obtained by the production method according to <9> into the negative electrode of the non-aqueous secondary battery.

As used herein, the term “water-soluble polymer” means a polymer that dissolves in 1 L of water at 25° C. in an amount of 7 g or more (a polymer whose solubility at 25° C. is 7 [g/1 L-H ₂ O] or more).
In this specification, a numerical range represented by "to" means a range including the numerical values before and after "to" as lower and upper limits.
In the present specification, the term "compound" is used to include the compound itself, its salts, and its ions. It also includes derivatives in which a part of the structure is changed, such as by introducing a substituent, to the extent that the desired effect is achieved.
In the present specification, when a substituent has a dissociable hydrogen atom (a group in which a hydrogen atom is dissociated by the action of a base), this substituent includes ions or salts.
For example, when a compound has a carboxy group, the carboxy group may exist as an anion by dissociating a hydrogen atom, and the anion may form a salt with a counterion (cation). Counterions are not particularly limited, and examples thereof include alkali metal ions such as lithium ions, sodium ions and potassium ions.
In the present specification, substituents, linking groups, etc. (hereinafter referred to as substituents, etc.) for which substitution or unsubstitution is not specified are intended to mean that the group may have an appropriate substituent. Therefore, in this specification, even when simply described as "- group" (eg, "alkyl group"), this "- group" (eg, "alkyl group") does not have a substituent In addition to embodiments (eg, "unsubstituted alkyl group"), embodiments having further substituents (eg, "substituted alkyl group") are also included. This also applies to compounds that are not specified as substituted or unsubstituted.
In this specification, when there are multiple substituents or the like indicated by a specific symbol, or when multiple substituents or the like are defined simultaneously or alternatively, the respective substituents or the like may be the same or different from each other. means good. Further, even if not otherwise specified, when a plurality of substituents and the like are adjacent to each other, they may be connected to each other or condensed to form a ring.
In this specification, when a polymer has a plurality of constituents with the same designation (indicated by the same general formula), each constituent may be the same or different.
As used herein, the term “non-aqueous secondary battery” is meant to include non-aqueous electrolyte secondary batteries and all-solid secondary batteries. As used herein, the term "non-aqueous electrolyte" means an electrolyte that does not substantially contain water. That is, the "non-aqueous electrolyte" may contain a small amount of water as long as the effects of the present invention are not impaired. In the present invention, the "non-aqueous electrolyte" has a water concentration of 200 ppm (by mass) or less, preferably 100 ppm or less, and more preferably 50 ppm or less. It is practically difficult to make the non-aqueous electrolyte completely anhydrous, and usually contains 1 ppm or more of water.
In this specification, the "solid content" used when describing the content or content ratio means components other than the dispersion medium described below.

The negative electrode composition and the negative electrode sheet of the present invention provide excellent cycle characteristics to a non-aqueous secondary battery using carbon-coated silicon oxide as a negative electrode active material by forming a negative electrode active material layer using them. can do. 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 negative electrode sheet of the present invention can be obtained. Moreover, according to the manufacturing method of the non-aqueous secondary battery of the present invention, the non-aqueous secondary battery of the present invention can be obtained.

FIG. 1 is a vertical cross-sectional view schematically showing the basic lamination structure of a non-aqueous 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 has an adsorption rate of 5 to 25% with respect to carbon-coated silicon oxide. In the present invention, the adsorption rate is a value determined by the method described in Examples below. When two or more types of water-soluble polymers are used, the value of the polymer with the highest adsorption rate shall be adopted. This adsorption rate is preferably 5 to 20%, more preferably 10 to 20%.
By incorporating the negative electrode active material layer produced using the negative electrode composition of the present invention into the secondary battery, the cycle life of the obtained secondary battery can be effectively increased. The reason for this is not yet clear, but when the polymer having the adsorption rate described above is contained in the binder, the water-soluble polymer becomes active in the negative electrode by, for example, fitting into the voids of the carbon coat layer (causing an anchor effect). It is presumed that one of the factors is the strong binding to the substance (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 aid, and the like. .

(binder)
Binders used in the present invention include the water-soluble polymers described above.
From the viewpoint of improving the cycle characteristics of the non-aqueous secondary battery, the adsorption rate is preferably 8% or more, more preferably 9% or more.
The structure of the water-soluble polymer is not particularly limited as long as it has the adsorption rate (5 to 25%).
The water-soluble polymer may be either a chain polymerized polymer or a stepwise polymerized polymer, preferably a chain polymerized polymer. There are no particular restrictions on the bond form of the chain polymer, and it may be random or block.

The water-soluble polymer preferably contains, for example, a component represented by the following general formula (1) or (2).

In general formula (1), R ¹ represents a hydrogen atom or a methyl group, L ¹ represents a single bond or a linking group (divalent), and R ² represents a substituent. * indicates a binding site for incorporation into a water-soluble polymer.
^In general formula ( ² ), R3 represents a hydrogen atom or a methyl group, and ^R4 and R5 represent a hydrogen atom or a substituent. * indicates a binding site for incorporation into a water-soluble polymer.

^The linking group that can be used 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 14-1000, more preferably 14-500, even more preferably 26-250.
Linking groups that can be used as L ¹ include, for example, alkylene groups, —O—, carbonyl groups, imino groups, and combinations thereof. As a combination of these, a connecting group formed by combining 2 to 6 groups selected from an alkylene group, —O—, a carbonyl group and an imino group is preferable, and a connecting group formed by combining 2 or 3 groups is more preferable.
L ¹ specifically includes -C(=O)-O-, -OC(=O)-, -NH-C(=O)-O-, -OC(=O)-NH- , -NH-C(=O)-NH-, and an alkylene group, more preferably an alkylene group.
The alkylene group that can be used as L ¹ may be either linear or branched, and the number of carbon atoms in the alkylene group is preferably 1 to 10, more preferably 1 to 8, still more preferably 1 to 6, and can be 1 to 4. Most preferably, it is a methylene group, an ethylene group, an ethylethylene group or a propylene group.
The chemical formula weight of L ¹ is preferably 14-200, more preferably 14-150, even more preferably 14-100.

R ² is not particularly limited as long as it is a substituent having no acid group. The chemical formula weight of R ² is preferably 15-200, more preferably 15-150, even more preferably 15-100. Examples of R ² include a hydroxy group, an alkyloxy group, an alkyl group, an amide group and a sulfonamide group, preferably a hydroxy group or an alkyloxy group.
The alkyl group in the alkyloxy group may be linear, branched or cyclic. The number of carbon atoms in the alkyl group is preferably 1 to 10, more preferably 1 to 8, still more preferably 1 to 6, particularly preferably 1 to 4, and is any one of a methyl group, an ethyl group and an isopropyl group. is most preferred.
The alkyl group has the same definition as the alkyl group in the above alkyloxy group, and the preferred range is also the same.

Each chemical formula weight of R ⁴ and R ⁵ is preferably 1-200, more preferably 1-150, even more preferably 1-60.
Alkyl groups are preferred as substituents that can be taken as R ⁴ and R ⁵ .
The alkyl group has the same definition as the alkyl group in the alkyloxy group that can be used as R ² above, and the preferred range is also the same. It is also preferred that the alkyl groups that can be used as R ⁴ and R ⁵ further have substituents. Examples of such substituents include hydroxy groups, alkylcarbonyl groups, amide groups, and urethane bond-containing groups (--NH--CO--O--R ^b (R ^b represents an alkyl group). A hydroxy group is preferred as a substituent of the alkyl group that can be used as R ⁴ and R ⁵ .
The alkyl group in the alkylcarbonyl group has the same meaning as the alkyl group in the alkyloxy group that can be used as R ² above, and the preferred range is also the same. The alkyl group represented by R ^b has the same definition as the alkyl group in the alkyloxy group that can be used as R ² above, and the preferred range is also the same.
Both R ⁴ and R ⁵ are preferably a hydrogen atom, or one is a hydrogen atom and the other is a hydroxyalkyl group.

The component represented by general formula (1) or (2) above preferably does not have an acid group.

The ratio of the component represented by the general formula (1) or (2) in the water-soluble polymer (the ratio of the component represented by the general formula (1) in the water-soluble polymer and the above The total ratio of the components represented by general formula (2)) is not particularly limited as long as the water-soluble polymer as a whole exhibits the above adsorption rate. For example, the proportion of the component represented by the general formula (1) or (2) can be 30% by mass or more. In addition, the proportion of the component represented by the general formula (1) or (2) is preferably 50% by mass or more, more preferably 70% by mass or more, and preferably 90% by mass or more. More preferably, it is particularly 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 constituents represented by general formula (1) or (2). ) or (2), and more preferably 2 to 4 components represented by general formula (1) or (2). By including two or more constituents represented by the general formula (1) or (2) in the water-soluble polymer, the adsorption rate to carbon-coated silicon oxide is improved and the negative electrode when used in the negative electrode sheet. It is possible to simultaneously improve the mechanical properties of the sheet, and as a result, it is possible to further improve the cycle characteristics of the secondary battery.
In addition, as a form containing two or more constituent components represented by general formula (1) or (2), two or more constituent components represented by general formula (1) are included, and general formula (2) A form that does not contain the constituents represented by the general formula (2), a form that contains two or more constituents represented by the general formula (2), and a form that does not contain the constituents represented by the general formula (1), and in the general formula (1) Examples include a form containing both the component represented by formula (2) and the component represented by formula (2).

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

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

When the water-soluble polymer contains constituents other than the constituents represented by the general formula (1) or (2) as constituents having no acid group, such constituents are not particularly limited. Examples include components derived from vinyl monomers such as styrene, maleimide, N-vinylacetamide, vinyl esters and vinyl ethers.

The water-soluble polymer may have a component having an acid group. The "acid group" of a component having an acid group means a group having a dissociative proton or a salt thereof. Examples include a carboxy group, a sulfo group, a phosphate group (--OP(=O)(OH) ₂ ), a phosphonic acid group or (--P(=O)(OH) ₂ ) and salts thereof. and a sulfo group or a salt thereof are preferred, and a carboxy group or a salt thereof is more preferred. Salt forms include, for example, alkali metal salts (eg, lithium salts, sodium salts, potassium salts, etc.).

The component having the acid group is not particularly limited, and the component usually contains 1 to 3 acid groups, preferably 1 or 2 groups, and more preferably 1 group. The component having an acid group that the water-soluble polymer may have is preferably, 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. * indicates a binding site for incorporation into a water-soluble polymer.

The linking group that can be used as L ² is not particularly limited, and examples thereof include an alkylene group, an arylene group, a carbonyl group, —O—, an imino group, or a linking group in which two or more of these are combined.

The alkylene group that can be used as L ² may be either linear or branched, and the number of carbon atoms in the alkylene group is preferably 1 to 10, more preferably 1 to 8, still more preferably 1 to 6, and can be 1 to 4. Especially preferred. Specific examples of this alkylene group include, for example, a methylene group, an ethylene group, a propylene group and a dimethylethylene group.

The number of carbon atoms in the arylene group that can be taken as L ² is preferably 6-30, more preferably 6-20, still more preferably 6-15, and even more preferably 6-10. Specific examples of arylene groups include phenylene groups and naphthylene groups.

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, -O- and an imino group, and a linking group combining 2 to 10 types A linking group in which 2 to 7 types are combined is preferable, and a linking group in which 2 to 4 types are combined is even more preferable.
Specific examples of the above-mentioned "linking group combining two or more types" include, for example, "carbonyl group-imino group-alkylene group" and "carbonyl group-O-alkylene group".

The proportion of the component having an acid group in the water-soluble polymer is preferably 30% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, and 3% by mass or less. More preferably, it is particularly preferably 2% by mass or less, and most preferably the water-soluble polymer does not contain a component having an acid group.

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

The weight average molecular weight of the water-soluble polymer used in the present invention is preferably 900,000 or less, more preferably 800,000 or less, and particularly preferably 700,000 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, and even more preferably 100,000 or more.
Moreover, from the viewpoint of the bending resistance of the negative electrode sheet, the weight-average molecular weight of the water-soluble polymer is preferably 350,000 or more.
In the present specification, the weight average molecular weight of a polymer is a value obtained by measuring by the method described in the Examples section below.

Various factors affect the adsorption rate of the water-soluble polymer used in the present invention. For example, there are physical interaction with the carbon coat layer, anchoring effect on voids of the carbon coat layer, and charge interaction with silicon oxide. Therefore, it is difficult to unambiguously explain whether such a polymer structure can achieve the desired adsorption rate. It is presumed that the adsorption rate to carbon-coated silicon oxide can be varied within various ranges by controlling the molecular weight of the compound.

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

In addition, 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, and 4 parts by mass with respect to 100 parts by mass of carbon-coated silicon oxide. Part or more is more preferable, and 8 parts by mass or more is even more preferable. 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 24 parts by mass or less, and 18 parts by mass or less with respect to 100 parts by mass of carbon-coated silicon oxide. More preferred.
The content of the water-soluble polymer in the negative electrode composition is 2 parts by mass or more with respect to 100 parts by mass of carbon-coated silicon oxide, so that the carbon-coated silicon oxide can be coated. Cycle characteristics of the secondary battery can be improved.

The binder used in the present invention can contain polymers other than the above water-soluble polymers within a range that does not impair the effects of the present invention. Such polymers include, for example, water-insoluble polymers, and polymers having an adsorption rate to carbon-coated silicon oxide of less than 5% or greater than 20%. Specific examples of such polymers include, but are not limited to, polymer B shown in Table 1 below.

(Negative electrode active material)
The negative electrode active material used in the present invention contains carbon-coated silicon oxide (SiOx (0<x≦1.5)). Carbon-coated silicon oxide can reversibly store and release lithium ions.
The silicon oxide may be carbon-coated over the entire surface, or may have a portion not coated with carbon. Even if the entire surface of silicon oxide is carbon-coated, the carbon-coated layer itself has a large number of voids.
The ratio of carbon atoms in the carbon-coated silicon oxide (the total of the carbon coating layer and silicon oxide) is not particularly limited, and from the viewpoint of achieving both conductivity and electric capacity, for example, 0.2 to 5% by mass is preferable. , more preferably 0.5 to 5% by mass, still more preferably 0.5 to 3% by mass, and particularly preferably 1 to 3% by mass.
Carbon-coated silicon oxide may be a commercially available product, and can be prepared by carbon-coating silicon oxide, for example, referring to 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. Hereinafter, in the description of the negative electrode active material used in the present invention, negative electrode active materials other than the carbon-coated silicon oxide are referred to as "other negative electrode active materials".
Other negative electrode active materials are preferably those capable of reversibly intercalating and deintercalating lithium ions. The material is not particularly limited as long as it has the above properties, and examples thereof include carbonaceous materials, metal oxides, metal composite oxides, lithium alloys, negative electrode active materials capable of forming an alloy with lithium, and the like.
The lithium alloy is not particularly limited as long as it is an alloy normally used as a negative electrode active material for secondary batteries, and examples thereof include lithium aluminum alloys.
The negative electrode active material capable of forming an alloy with lithium is not particularly limited as long as it 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 negative electrode active materials containing tin atoms include Sn, SnO, SnO ₂ , SnS, SnS ₂ , active materials containing silicon atoms and tin atoms, and the like. Also included are composite oxides with lithium oxide, such as Li ₂ SnO ₂ .
Among these, carbonaceous materials are preferably used as other negative electrode active materials from the viewpoint of reliability.

Other carbonaceous materials used as negative electrode active materials are materials that are substantially made of carbon. For example, carbon black such as petroleum pitch, graphite (natural graphite, artificial graphite such as vapor growth graphite, etc.), and carbonaceous materials obtained by baking various synthetic resins such as PAN (polyacrylonitrile) resin or furfuryl alcohol resin Materials can be mentioned. Furthermore, various carbon fibers such as PAN-based carbon fiber, cellulose-based carbon fiber, pitch-based carbon fiber, vapor growth carbon fiber, dehydrated PVA (polyvinyl alcohol)-based carbon fiber, lignin carbon fiber, vitreous carbon fiber and activated carbon fiber. , mesophase microspheres, graphite whiskers and tabular graphite.

Other metal oxides and metal composite oxides applied as negative electrode active materials are not particularly limited as long as they are oxides capable of intercalating and deintercalating lithium. Chalcogenite, which is a reaction product with an element belonging to Group 16 of the Norms Table, is also preferred. The term “amorphous” as used herein means a broad scattering band having an apex in the region of 20° to 40° in terms of 2θ value in an X-ray diffraction method using CuKα rays, and a crystalline diffraction line. may have
Among the compound group consisting of the above amorphous oxides and chalcogenides, amorphous oxides of metalloid elements and the above chalcogenides are more preferable, elements of groups 13 (IIIB) to 15 (VB) of the periodic table, Particularly preferred are oxides of Al, Ga, Si, Sn, Ge, Pb, Sb and Bi, or a combination of two or more thereof (excluding oxides containing Si), or chalcogenides. Specific examples of preferred amorphous oxides and chalcogenides include Ga ₂ O ₃ , GeO, PbO, PbO ₂ , Pb ₂ O ₃ , Pb ₂ O ₄ , Pb ₃ O ₄ , Sb ₂ O ₃ and Sb ₂ . _O4 _, _Sb2O8Bi2O3 _, _Sb2O5 , _Bi2O3 , _Bi2O4 , _GeS , _PbS , _PbS2 _, _Sb2S3 _and _Sb2S5 _are _preferred .

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

Other negative electrode active materials preferably contain titanium atoms. More specifically, TiNb ₂ O ₇ (niobium titanate [NTO]) and Li ₄ Ti ₅ O ₁₂ (lithium titanate [LTO]) have small volume fluctuations when absorbing and desorbing lithium ions, and are therefore suitable for rapid charging. It is preferable in that it has excellent discharge characteristics, suppresses deterioration of the electrode, and can improve 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 is preferably particulate. The volume-based median diameter D50 of carbon-coated silicon oxide and other negative electrode active materials is preferably 0.1 to 60 μm. A conventional pulverizer or classifier is used to obtain a predetermined particle size. For example, a mortar, a ball mill, a sand mill, a vibrating ball mill, a satellite ball mill, a planetary ball mill, a whirling jet mill, a sieve, or the like is preferably used. At the time of pulverization, wet pulverization can also be performed in which water or an organic solvent such as methanol is allowed to coexist. Classification is preferably carried out in order to obtain a desired particle size. The classification method is not particularly limited, and a sieve, an air classifier, or the like can be used as desired. Both dry and wet classification can be used.

The median diameter D50 of carbon-coated silicon oxide is also preferably 0.1 to 30 μm, more preferably 0.5 to 20 μm, and particularly preferably 2 to 8 μm.
The median diameter D50 can be determined by a laser diffraction method, for example, using SALD-2300 (trade 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 compounding ratio (carbon-coated silicon oxide/graphite, based on mass) is preferably 0.1 or more, more preferably 0.2 or more, and further preferably 0.3 or more. preferable. Although there is no particular upper limit for the ratio of carbon-coated silicon oxide to graphite, it is practically 4 or less, preferably 3 or less, and more preferably 2 or less.
The content of carbon-coated silicon oxide in the negative electrode active material is not particularly limited, and can be, for example, 10 to 90% by mass, preferably 10 to 50% by mass, more preferably 15 to 40% by mass.
When forming the negative electrode active material layer, the mass (mg) (basis weight) of 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. do not have. It can be determined appropriately according to 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, and the total is preferably 10 to 98% by mass based on 100% by mass of solid content. 15 to 95% by mass is more preferable.

(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" is water or a mixture of water and a water-soluble organic solvent. Further, the "water-soluble organic solvent" is an organic solvent compatible with water, and examples thereof include N-methylpyrrolidone, methanol, ethanol, acetone, tetrahydrofuran and the like.

(Conductivity aid)
The negative electrode composition of the present invention can also contain a conductive aid.
There are no particular restrictions on the conductive aid, and any commonly known conductive aid can be used. For example, 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, vapor-grown carbon fiber, or carbon nanotube, which are electronic conductive materials Carbon fibers such as carbon fibers such as graphene or fullerene may be used, metal powders such as copper and nickel, metal fibers may be used, and conductive polymers such as polyaniline, polypyrrole, polythiophene, polyacetylene, and polyphenylene derivatives may be used.
In the present invention, when a negative electrode active material and a conductive aid are used in combination, among the above conductive aids, Li insertion and release do not occur when the secondary battery is charged and discharged, and do not function as a negative electrode active material. is used as a conductive aid. Therefore, among conductive aids, those that can function as a negative electrode active material in a negative electrode active material layer during charging and discharging of a secondary battery are classified as negative electrode active materials instead of conductive aids. Whether or not it functions as a negative electrode active material when a secondary battery is charged and discharged is not univocally determined by the combination with the negative electrode active material.

Conductive aids may be used alone or in combination of two or more.
The content of the conductive aid in the negative electrode composition is preferably 1 to 30% by mass, more preferably 1 to 15% by mass, and even more preferably 3 to 10% by mass based on 100% by mass of solid content.

The shape of the conductive aid is not particularly limited, but it is preferably particulate. The median diameter D50 of the conductive aid is not particularly limited, and is preferably 0.01 to 50 μm, preferably 0.02 to 10.0 μm, for example.

(other additives)
The negative electrode composition of the present invention may optionally contain, as components other than the components described above, a lithium salt, an ionic liquid, a thickener, an antifoaming agent, a leveling agent, a dehydrating agent, an antioxidant, and the like. can be done. In addition, a cross-linking agent for chemically cross-linking the water-soluble polymer (such as one that undergoes a cross-linking reaction by radical polymerization, condensation polymerization, or ring-opening polymerization), and a polymerization initiator (that generates acid or radicals by heat or light) etc.).
Regarding the conductive aid and other additives, for example, International Publication No. WO 2019/203334, JP-A-2015-46389, etc. can be referred to.

[Negative electrode sheet]
The negative electrode sheet of the present invention has a layer (negative electrode active material layer) configured (formed) using the negative electrode composition of the present invention. The negative electrode sheet of the present invention only needs to have a negative electrode active material layer. It may be a sheet formed of This negative electrode sheet is usually a sheet having a structure in which a negative electrode active material layer is laminated on a current collector. The negative electrode sheet of the present invention may have other layers such as a protective layer (release sheet) and a coat layer.
The negative electrode sheet of the present invention can be suitably used as a material constituting a negative electrode active material layer of a secondary battery.

[Manufacturing method of 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 base material, and the composition for a negative electrode of the present invention is applied thereon (may be via another layer) to form a coating film, which is dried to form a base material. An electrode sheet having a negative electrode active material layer (coated dry layer) thereon can be obtained.

[Non-aqueous secondary battery]
The non-aqueous secondary battery of the present invention means all devices in which ions pass between the positive and negative electrodes through an electrolyte due to charging and discharging, and energy is stored and released at the positive and negative electrodes. That is, the term "non-aqueous secondary battery" as used in the present invention includes both batteries and capacitors (for example, lithium ion capacitors). From the viewpoint of energy storage capacity, the non-aqueous secondary battery of the present invention is preferably used for battery applications (not a capacitor).

The non-aqueous secondary battery of the present invention will be described by taking the form of a non-aqueous electrolyte secondary battery as an example, but the secondary battery of the present invention is not limited to the non-aqueous electrolyte secondary battery. It broadly includes all non-aqueous secondary batteries including solid secondary batteries.
A non-aqueous electrolyte secondary battery, which is a preferred embodiment of the present invention, has a configuration including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode. The positive electrode has a positive electrode current collector and a positive electrode active material layer in contact with the positive electrode current collector, and the negative electrode has a negative electrode current collector and a negative electrode active material layer in contact with the negative electrode current collector. In the non-aqueous 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 schematic cross-sectional view showing a laminated structure of a general non-aqueous electrolyte secondary battery 10 including working electrodes when operated as a battery. The non-aqueous electrolyte secondary battery 10 has a laminated structure having, when viewed from the negative electrode side, 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 in this order. is doing. The space between the negative electrode active material layer and the positive electrode active material layer is filled with a non-aqueous electrolyte (not shown) and separated by the separator 3 . The separator 3 has pores and functions as a positive/negative separator that insulates the positive/negative electrodes while permeating the electrolytic solution and ions under normal battery usage conditions. With such a structure, for example, in the case of a lithium ion secondary battery, during charging, electrons (e ⁻ ) are supplied to the negative electrode side through an external circuit, and at the same time lithium ions (Li ⁺ ) are released from the positive electrode through the electrolyte. It moves and accumulates at the negative electrode. On the other hand, during discharge, the lithium ions (Li ⁺ ) accumulated in the negative electrode are returned to the positive electrode side through the electrolyte, and electrons are supplied to the operating portion 6 . In the illustrated example, a light bulb is employed in the actuation portion 6, which is lit by the discharge.
In the present invention, the negative electrode current collector 1 and the negative electrode active material layer 2 are collectively referred to as a negative electrode, and the positive electrode active material layer 4 and the positive electrode current collector 5 are collectively referred to as a positive electrode.

The non-aqueous secondary battery of the present invention comprises a positive electrode active material, a non-aqueous electrolyte, a solid electrolyte material, other members, etc., except that the negative electrode composition of the present invention is used to form a negative electrode active material layer. is not particularly limited. As these materials, members, and the like, those used in ordinary non-aqueous secondary batteries can be appropriately applied. As for the method for producing the non-aqueous secondary battery of the present invention, a normal method can be appropriately adopted, except that the negative electrode composition of the present invention is used to form the negative electrode active material layer. For example, JP-A-2016-201308, JP-A-2005-108835, JP-A-2012-185938, and International Publication No. 2020/067106 can be referred to as appropriate.

The non-aqueous secondary battery of the present invention can be used, for example, in notebook computers, pen-input computers, mobile computers, e-book players, mobile phones, cordless phone slaves, pagers, handy terminals, mobile facsimiles, mobile copiers, mobile printers, and headphone stereos. , video movies, liquid crystal televisions, handy cleaners, portable CDs, minidiscs, electric shavers, transceivers, electronic notebooks, calculators, portable tape recorders, radios, backup power supplies, memory cards, and other electronic devices. In addition, for consumer use, it can be installed in automobiles, electric vehicles, motors, lighting equipment, toys, game devices, road conditioners, watches, strobes, cameras, medical devices (pacemakers, hearing aids, shoulder massagers, etc.). It can also be combined with a solar cell.

The present invention will be described in more detail based on examples. It should be noted that the present invention is not to be construed as being limited by these examples, except as defined by the present invention.

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

<Synthesis of polymers 2 to 19 and c1 to c3 (synthesis of polymers Nos. 2 to 19 and c1 to c3 in Table 1 below>
In the synthesis of Polymer 1, Polymers 2 to 19 and c1 to c3 were prepared in the same manner as Polymer 1, except that the monomers shown in Table 1 below were used as monomers leading to the constituent components at the mass ratios shown in Table 1 below. Synthesized.

<Synthesis of polymers 20 to 23, c4 and c5 (synthesis of polymers No. 20 to 23, c4 and c5 in Table 3 below>
In the synthesis of Polymer 1, Polymers 20 to 23, c4 and c5 were prepared in the same manner as Polymer 1 except that the monomers shown in Table 3 below were used as monomers leading to the constituent components at the mass ratios shown in Table 3 below. was synthesized.

<Synthesis of polymers 25 to 28, c6 and c7 (synthesis of polymers Nos. 25 to 28, c6 and c7 in Table 5 below>
In the synthesis of Polymer 1, Polymers 25 to 28, c6 and c7 were prepared in the same manner as Polymer 1 except that the monomers shown in Table 3 below were used as the monomers leading to the constituent components at the mass ratios shown in Table 5 below. was synthesized.

[Carbon-coated silicon oxide]
Active materials 1 to 3 shown in Table A below (all manufactured by Osaka Titanium Co., Ltd.) were used as the carbon-coated silicon oxide in the preparation of the negative electrode composition described later.

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

(Measurement of adsorption rate)
40 mg of the aqueous polymer solution was poured into a 50 mL sample bottle in terms of solid content. The mixture was diluted with ion-exchanged water so as to obtain 40.00 g including the polymer to obtain an aqueous polymer solution having a polymer concentration of 0.1% by mass.
800 mg of carbon-coated silicon oxide was placed in a 15 mL sample bottle. After adding 8 g of the polymer aqueous solution having a polymer concentration of 0.1% by mass to the sample bottle, the mixture was stirred at 80 rpm at 25° C. for 1 hour using a mix rotor. After standing at 25° C. for 30 minutes, the supernatant was filtered through a 0.45 μm filter to obtain a filtrate. GPC measurement was performed under the conditions described above, and the adsorption rate (%) was calculated by applying the peak height (1) of the aqueous polymer solution and the peak height (2) of the filtrate to the following formula. The adsorption rate is shown in Table 2 below together with the weight average molecular weight (adsorbed molecular weight) obtained by GPC measurement.

Adsorption rate (%) = 100 - {100 x peak height (2) / peak height (1)}

The adsorbed molecular weight was calculated from the difference between the GPC data of the aqueous polymer solution and the GPC data of the filtrate. The carbon-coated silicon oxide is the same as that used in the negative electrode composition.

[Preparation of negative electrode composition 1 (composition No. 1 in Table 2 below)]
In a 60 mL ointment container (manufactured by Umano Kagaku Co., Ltd.), 30 parts by mass of active material 1 described in Table A above, 70 parts by mass of graphite (trade name: MAG-D, manufactured by Hitachi Chemical Co., Ltd.), acetylene black (trade name : Denka Black, manufactured by Denka Co., Ltd.), 5 parts by mass of Polymer 1, and 22.5 parts by mass of distilled water are added, and dispersed at 2000 rpm for 10 minutes using a foaming mixer (trade name, manufactured by THINKY Co., Ltd.). did. A negative electrode composition 1 was obtained by adding 27 parts by mass of distilled water to the dispersed liquid and dispersing the mixture at 2000 rpm for 10 minutes using a bubble removing mixer.

[Preparation of non-aqueous electrolyte secondary battery (2032 type coin battery) 1 (No. 1 battery in Table 2 below)]
The negative electrode composition 1 thus obtained was applied onto a copper foil having a thickness of 20 μm with an applicator and dried at 80° C. for 1 hour. Then, after pressing with a press, the sheet was dried in vacuum at 150° C. for 6 hours to obtain a negative electrode sheet having a negative electrode active material layer with a thickness of 25 μm.
A disc with a diameter of 13.0 mm was cut out from the above negative electrode sheet and used to form a negative electrode.
Lithium foil (thickness 50 μm, 14.5 mm φ) and polypropylene separator (thickness 25 μm, _16.0 mm φ) are stacked in this order. I let you in. The separator was further impregnated with 200 μL of the electrolytic solution, and the negative electrode sheet was stacked so that the negative electrode active material layer surface was in contact with the separator. After that, the 2032 type coin case was crimped to prepare a non-aqueous electrolyte secondary battery 1 (a battery having a laminate consisting of Li foil-separator-negative electrode active material layer-copper foil).

[Preparation of negative electrode compositions 2 to 19 and c1 to c3 (compositions of Nos. 2 to 19 and c1 to c3 in Table 2 below)]
In the preparation of the negative electrode composition 1, the negative electrode composition was prepared in the same manner as the negative electrode composition 1, except that polymers 2 to 19 and c1 to c3 described in Table 1 below were used instead of the polymer 1. 2-19 and c1-c3 were prepared.

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

[Test Example 1] Evaluation of Cycle Characteristics The discharge capacity retention rate of each coin battery was measured with a charge/discharge evaluation device: TOSCAT-3000 (trade name, manufactured by Toyo System Co., Ltd.). The battery was charged at a C rate of 0.2C (the rate at which the battery is fully charged in 5 hours) until the battery voltage reached 0.02V. Discharge was performed at a C rate of 0.2C until the battery voltage reached 1.5V. Each coin battery was initialized by repeating 3 cycles of charging and discharging, with one charging and one discharging as one cycle of charging and discharging.
After initialization, charging was performed at 0.5C until reaching 0.02V. Discharge was performed at 0.5C until reaching 1.5V. Cycle characteristics were evaluated by repeating 50 charge/discharge cycles, with one charge/discharge cycle being defined as one charge/discharge cycle. Assuming that the discharge capacity at the first cycle after initialization (initial discharge capacity) is 100%, the discharge capacity retention rate at the 50th cycle (100 × “50th cycle discharge capacity” / “initial discharge capacity”) was calculated. , was applied to the following evaluation ranks, and the cycle characteristics were evaluated. Polymer species and their properties are shown in Table 1, and test evaluation results using each composition are shown in Table 2.

-Evaluation rank of discharge capacity retention rate (cycle characteristics)-
1: 95% or more 2: 90% or more and less than 95% 3: 85% or more and less than 90% 4: less than 85%

<Notes to Tables 1 and 2>
The abbreviations of the monomers leading to the constituents are explained. Also, the structures of the constituents derived from the monomers are described.
(Constituent without acid group)
HEA: 2-hydroxyethyl acrylate HEAA: N-(2-hydroxyethyl) acrylamide Aam: acrylamide MEA: 2-methoxyethyl acrylate

(Constituent with 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, volume-based average primary particle diameter 3 µm (solid content 15% by mass), this latex is non- Water soluble.
High acid group polymer: 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)
High molecular weight polymer: random copolymer synthesized in the same manner as polymer 1 above (“HEAA/HEA”, HEAA:HEA = 50:50 (mass ratio), Mw = 400,000)

"Content in polymer A (% by mass)": means the content of the component having an acid group in polymer A.
"Content 1 (parts by mass)": When the content of carbon-coated silicon oxide in the negative electrode composition is 100 parts by mass, the content of polymer A with respect to 100 parts by mass of carbon-coated silicon oxide means.
"Content in binder (% by mass)": means the ratio of the content of the water-soluble polymer defined in the present invention to the total polymer contained in the binder.
"Content 2 (parts by mass)": When the content of carbon-coated silicon oxide in the negative electrode composition is 100 parts by mass, the content of polymer B with respect to 100 parts by mass of carbon-coated silicon oxide means. In addition, content of "latex" is content of solid content.
"Water-soluble/water-insoluble": "water" means that 7 g or more was dissolved in 1 L of water at 25°C, and "non-aqueous" means that less than 7 g was dissolved in 1 L of water at 25°C. means. All of the polymers A, including those used in the comparative examples, are water-soluble.

No. Polymer A used in the negative electrode compositions of c1 to c3 has an adsorption rate of less than 5% to carbon-coated silicon oxide. No. Nos. c1 to c3 produced using the negative electrode compositions. Batteries of c1 and c3 were inferior in cycle characteristics.
On the other hand, it can be seen that the batteries (Nos. 1 to 19) produced using the negative electrode compositions (Nos. 1 to 19) of the present invention are excellent in cycle characteristics.

[Preparation of negative electrode compositions 20 to 24, c4 and c5 (compositions of Nos. 20 to 24, c4 and c5 in Table 4 below)]
In the preparation of the negative electrode composition 1, instead of the active material 1 and polymer 1 used in the preparation of the negative electrode composition 1, the polymers and active materials shown in Table 4 below were used. Negative electrode compositions 20 to 24, c4 and c5 were prepared in the same manner as composition 1.

[Preparation of non-aqueous electrolyte secondary batteries 20 to 24, c4 and c5 (batteries No. 20 to 24, c4 and c5 in Table 4 below)]
In the production of the non-aqueous electrolyte secondary battery 1, except that the negative electrode compositions 20 to 24, c4 and c5 listed in Table 4 below were used instead of the negative electrode composition 1, the non-aqueous electrolyte 2 Non-aqueous electrolyte secondary batteries 20 to 24, c4 and c5 were produced in the same manner as in secondary battery 1.

[Preparation of negative electrode sheets 20 to 24, c4 and c5 (negative electrode sheets of Nos. 20 to 24, c4 and c5 in Table 4 below)]
The negative electrode composition 20 was applied onto a copper foil having a thickness of 20 μm with an applicator and dried at 80° C. for 1 hour. Furthermore, the negative electrode sheet 20 was obtained by drying at 100 degreeC under vacuum for 6 hours. The negative electrode sheet 20 has a width of 50 mm, a length of 150 mm, and a thickness of 90 μm, and the thickness of the negative electrode active material layer is 70 μm.
In the production of the negative electrode sheet 20, the negative electrode composition 20 was replaced with the negative electrode compositions 21 to 24, c4 and c5 described in Table 4 below, in the same manner as the production of the negative electrode sheet 20. , negative electrode sheets 21 to 24, c4 and c5 were produced.

Using non-aqueous electrolyte secondary batteries 20 to 24, c4 and c5, the cycle characteristics were evaluated according to Test Example 1 above. In addition, bending resistance was evaluated according to Test Example 2 described later using negative electrode sheets 20 to 24, c4 and c5.
Polymer species and their properties are shown in Table 3 below, and the results of cycle property evaluation and flex resistance evaluation are shown in Table 4 below.

[Test Example 2] Bending resistance evaluation A test piece having a width of 10 mm, a length of 100 mm, and a thickness of 90 µm was cut out from the produced negative electrode sheet, and this test piece was placed in a cylindrical mandrel bending tester (BEVS 1603 (trade name, Allgood Co., Ltd.) The test piece was wound around the mandrel rod so that the current collector of the test piece was in contact with the mandrel rod.The diameter of the mandrel rod was gradually reduced from 32 mm, and the negative electrode active material of the test piece The diameter at which a crack first occurred in the layer was applied to the evaluation rank below to evaluate the bending resistance.

―Evaluation rank of bending resistance―
1: Less than 10 mm 2: 10 mm or more and less than 20 mm 3: 20 mm or more and less than 25 mm 4: 25 mm or more

<Notes to Tables 3 and 4>
"HEA", "AA", "HEAA", "Aam", "content in polymer A (% by mass)", "content 1 (parts by mass)", "content in binder (% by mass)" and "water" are the same as in "Notes to Tables 1 and 2" above.

No. Polymer A used in the negative electrode compositions of c4 and c5 has an adsorption rate of less than 5% to carbon-coated silicon oxide. No. Nos. c4 and c5 produced using the negative electrode compositions. Batteries of c4 and c5 were inferior in cycle characteristics. Also, No. The electrode sheet of c4 was also inferior in bending resistance.
On the other hand, it can be seen that the batteries (Nos. 20 to 24) produced using the negative electrode compositions (Nos. 20 to 24) of the present invention are excellent in cycle characteristics. Also, from a comparison between the negative electrode sheets 22 and 24 and the negative electrode sheets 20, 21 and 23, it can be seen that the use of a water-soluble polymer having a higher weight average molecular weight can further enhance the flex resistance.

In the negative electrode compositions 20 to 24, the content of active material 2 (30 parts by mass) and the content of graphite (70 parts by mass) were changed to "active material 2 (10 parts by mass), graphite (90 parts by mass)", "Active material 2 (20 parts by mass), graphite (80 parts by mass)", "Active material 2 (40 parts by mass), graphite (60 parts by mass)", "Active material 2 (50 parts by mass), graphite (50 parts by mass) parts)”, “active material 2 (60 parts by mass), graphite (40 parts by mass)”, it was confirmed that a battery with excellent cycle characteristics and a negative electrode sheet with excellent flex resistance were similarly obtained.

[Preparation of negative electrode compositions 25 to 29, c6 and c7 (compositions of Nos. 25 to 29, c6 and c7 in Table 6 below)]
In the preparation of the negative electrode composition 1, instead of the active material 1 and polymer 1 used in the preparation of the negative electrode composition 1, the polymers and active materials described in Table 6 below were used. Negative electrode compositions 25 to 29, c6 and c7 were prepared in the same manner as composition 1.

[Preparation of nonaqueous electrolyte secondary batteries 25 to 29, c6 and c7 (batteries Nos. 25 to 29, c6 and c7 in Table 6 below)]
In the production of the non-aqueous electrolyte secondary battery 1, except that the negative electrode compositions 25 to 29, c6 and c7 described in Table 6 below were used instead of the negative electrode composition 1, the non-aqueous electrolyte 2 Non-aqueous electrolyte secondary batteries 25 to 29, c6 and c7 were produced in the same manner as in secondary battery 1.

[Production of negative electrode sheets 25 to 29, c6 and c7 (negative electrode sheets of Nos. 25 to 29, c6 and c7 in Table 6 below)]
In the production of the negative electrode sheet 20, the negative electrode sheets 25 to 25 were prepared in the same manner as in the production of the negative electrode sheet 20, except that the negative electrode compositions 25 to 29, c6 and c7 were used instead of the negative electrode composition 20. 29, c6 and c7 were made.

Using the non-aqueous electrolyte secondary batteries 25 to 29, c6 and c7, the cycle characteristics were evaluated according to Test Example 1 above. In addition, bending resistance was evaluated according to Test Example 2 using the negative electrode sheets 25 to 29, c6 and c7.
Polymer species and their properties are shown in Table 5 below, and the results of cycle property evaluation and flex resistance evaluation are shown in Table 6 below.

<Notes to Tables 5 and 6>
"HEA", "AA", "HEAA", "Aam", "content in polymer A (% by mass)", "content 1 (parts by mass)", "content in binder (% by mass)" and "water" are the same as in "Notes to Tables 1 and 2" above.

No. Polymer A used in the negative electrode compositions of c6 and c7 has an adsorption rate of less than 5% to carbon-coated silicon oxide. No. Nos. c6 and c7 produced using the negative electrode compositions. Batteries of c6 and c7 were inferior in cycle characteristics.
In contrast, the batteries (Nos. 25 to 29) produced using the negative electrode compositions (Nos. 25 to 29) of the present invention are found to have excellent cycle characteristics and excellent flex resistance. Also, from a comparison between the negative electrode sheets 27 and 29 and the negative electrode sheets 25, 26 and 28, it can be seen that the use of a water-soluble polymer having a higher weight average molecular weight can further enhance the flex resistance.

In negative electrode compositions 25 to 29, the content of active material 3 (30 parts by mass) and the content of graphite (70 parts by mass) were changed to "active material 3 (10 parts by mass), graphite (90 parts by mass)", "Active material 3 (20 parts by mass), graphite (80 parts by mass)", "Active material 3 (40 parts by mass), graphite (60 parts by mass)", "Active material 3 (50 parts by mass), graphite (50 parts by mass) parts)”, “active material 3 (60 parts by mass), graphite (40 parts by mass)”, it was confirmed that a battery with excellent cycle characteristics and a negative electrode sheet with excellent flex resistance were similarly obtained.

While we have described our invention in conjunction with embodiments thereof, we do not intend to limit our invention in any detail to the description unless specified otherwise, which is contrary to the spirit and scope of the invention as set forth in the appended claims. I think it should be interpreted broadly.

This application claims priority based on Japanese Patent Application No. 2021-060334 filed in Japan on March 31, 2021 and Japanese Patent Application No. 2021-159546 filed in Japan on September 29, 2021. , the contents of which are hereby incorporated by reference as part of the present description.

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 (bulb)

Claims

Containing a binder containing a water-soluble polymer and carbon-coated silicon oxide,
A composition for a negative electrode, wherein the water-soluble polymer has an adsorption rate of 5 to 25% with respect to the carbon-coated silicon oxide.
The composition for a negative electrode according to claim 1, wherein the water-soluble polymer is a chain polymerization polymer.
3. The negative electrode composition according to claim 1, wherein the water-soluble polymer contains a component represented by the following general formula (1) or (2).

In general formula (1), R 1 represents a hydrogen atom or a methyl group, L 1 represents a single bond or a linking group, and R 2 represents a substituent. * indicates a binding site for incorporation into the water-soluble polymer.
In general formula ( 2 ), R3 represents a hydrogen atom or a methyl group, and R4 and R5 represent a hydrogen atom or a substituent. * indicates a binding site for incorporation into the water-soluble polymer.
The negative electrode composition according to any one of claims 1 to 3, wherein the content of the water-soluble polymer is 2 parts by mass or more with respect to 100 parts by mass of the carbon-coated silicon oxide.
The negative electrode composition according to claim 3, wherein the water-soluble polymer contains two or more constituents represented by the general formula (1) or (2).
The negative electrode composition according to any one of claims 1 to 5, which is a negative electrode slurry containing a dispersion medium.
A negative electrode sheet having a layer formed using the negative electrode composition according to any one of claims 1 to 6.
It has a positive electrode active material layer, a separator, and a negative electrode active material layer in this order, and the negative electrode active material layer is a layer formed using the negative electrode composition according to any one of claims 1 to 6. , non-aqueous secondary battery.
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 6.
A method for manufacturing a non-aqueous secondary battery, comprising incorporating the negative electrode sheet obtained by the manufacturing method according to claim 9 into the negative electrode of the non-aqueous secondary battery.