JP2022187229A - Coated electrode active material particles for lithium ion battery, electrode for lithium ion battery, and manufacturing method of coated electrode active material particles for lithium ion battery - Google Patents

Abstract

To provide coated electrode active material particles for a lithium ion battery which can suppress the side reaction that occurs between an electrolytic solution and the coated electrode active material particles even when used in a high temperature environment, and can reduce the increase in the internal resistance value of the lithium ion battery.SOLUTION: In coated electrode active material particles for a lithium ion battery, at least a part of the surface of the electrode active material particles is coated with a coating layer, and the coating layer includes particles made of a polymer having lithium ion conductivity, a coating resin, and a conductive aid.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to coated electrode active material particles for lithium ion batteries, electrodes for lithium ion batteries, and methods for producing coated electrode active material particles for lithium ion batteries.

Lithium ion batteries have come to be widely used in various applications as secondary batteries capable of achieving high energy density and high power density.

For example, Patent Document 1 discloses a polymer of a monomer composition comprising an ester compound of a monohydric aliphatic alcohol having 1 to 12 carbon atoms and (meth)acrylic acid and an anionic monomer. , an active material-coating resin composition comprising a polymer having an acid value of 30 to 700, and a coating layer comprising the active material-coating resin composition on at least a part of the surface of the active material. A coated active material is disclosed.

JP 2017-160294 A

Lithium-ion batteries have become widely used in a variety of applications, including, for example, high temperature environments.
In a conventional lithium-ion battery using a coated active material, when used in a high-temperature environment, a side reaction occurs between the electrolyte and the coated active material, causing deterioration of the lithium-ion battery (specifically, internal There is a problem that the resistance value may increase), and there is room for improvement.

INDUSTRIAL APPLICABILITY The present invention provides a coated electrode for a lithium ion battery that can suppress the side reaction that occurs between the electrolytic solution and the coated electrode active material particles even when used in a high temperature environment, and can reduce the increase in the internal resistance value of the lithium ion battery. An object of the present invention is to provide active material particles. Another object of the present invention is to provide a lithium ion battery electrode containing the coated electrode active material particles for lithium ion batteries, and a method for producing the coated electrode active material particles for lithium ion batteries.

As a result of intensive studies by the present inventors in order to solve the above problems, deposition of a reaction product (SEI: Solid Electrolyte Interphase) generated by direct contact between the electrode active material particles and the electrolytic solution is a lithium ion battery. was found to be a factor in the increase in the internal resistance value of
The present inventors have found that in a coated electrode active material particle for a lithium ion battery in which at least a part of the surface of the electrode active material particle is coated with a coating layer, the electrode active material particle and the electrolytic solution are separated from each other by the coating resin that constitutes the coating layer. Although it was considered to prevent the contact between the electrolyte and the coated electrode active material particles to suppress the side reaction, it was not possible to sufficiently reduce the increase in the internal resistance value of the lithium ion battery.
Therefore, the present inventors have made further intensive studies to solve the above problems. The inventors have found that a side reaction occurring between the electrolytic solution and the coated electrode active material particles can be suppressed, and an increase in the internal resistance value of the lithium ion battery can be effectively reduced, and the present invention has been achieved.

That is, the present invention provides a coated electrode active material particle for a lithium ion battery in which at least a part of the surface of the electrode active material particle is coated with a coating layer, wherein the coating layer is made of a polymer having lithium ion conductivity. A coated electrode active material particle for a lithium ion battery containing particles, a coating resin, and a conductive aid; and an electrode active material layer containing the coated electrode active material particle for a lithium ion battery and an electrolytic solution containing an electrolyte and a solvent. A lithium ion battery electrode, wherein the weight ratio of the coating resin contained in the lithium ion battery electrode is 1 to 10% by weight based on the weight of the lithium ion battery electrode; The present invention relates to a method for producing the coated electrode active material particles for a lithium ion battery, which comprises a step of mixing the active material particles, the polymer particles having lithium ion conductivity, the coating resin, the conductive aid and the organic solvent, and then removing the solvent.

According to the present invention, even when used in a high-temperature environment, it is possible to suppress the side reaction that occurs between the electrolytic solution and the coated electrode active material particles, and to reduce the increase in the internal resistance value of the lithium ion battery. A coated electrode active material particle for an ion battery can be provided.

<Coated electrode active material particles for lithium ion battery>
The coated electrode active material particles for lithium ion batteries of the present invention are coated electrode active material particles for lithium ion batteries in which at least a part of the surface of the electrode active material particles is coated with a coating layer, wherein the coating layer contains lithium ions It contains conductive polymer particles, a coating resin, and a conductive aid.
With such a configuration, contact between the electrode active material particles and the electrolytic solution can be prevented, and side reactions that occur between the electrolytic solution and the coated electrode active material particles can be suppressed. An increase in resistance value can be effectively reduced.

(Electrode active material particles)
Examples of the electrode active material particles include positive electrode active material particles and negative electrode active material particles. It can be selected as appropriate.

Examples of positive electrode active material particles include composite oxides of lithium and transition metals {composite oxides containing one type of transition metal (LiCoO ₂ , LiNiO ₂ , LiAlMnO ₄ , LiMnO ₂ and LiMn ₂ O ₄ , etc.), transition metal elements are two kinds of composite oxides (for example, LiFeMnO ₄ , LiNi _1-x Co _x O ₂ , LiMn _1-y Co _y O ₂ , LiNi _1/3 Co _1/3 Al _1/3 O ₂ and LiNi _0.8 Co _0.15 Al _0.05 O ₂ ) and a composite oxide containing three or more metal elements [for example, LiM _a M′ _b M″ _c O ₂ (M, M′ and M″ are different transition metals, _element and _satisfies a _{+ b + c} = ₁ . ₄ ), transition metal oxides (eg MnO ₂ and V ₂ O ₅ ), transition metal sulfides (eg MoS ₂ and TiS ₂ ) and conductive polymers (eg polyaniline, polypyrrole, polythiophene, polyacetylene and poly-p-phenylene and polyvinyl carbazole).
These positive electrode active material particles may be used singly or in combination of two or more.
The lithium-containing transition metal phosphate may have a transition metal site partially substituted with another transition metal.

The volume average particle diameter of the positive electrode active material particles is preferably 0.01 to 100 μm, more preferably 0.1 to 35 μm, and further preferably 2 to 30 μm, from the viewpoint of the electrical characteristics of the battery. preferable.

Examples of the negative electrode active material particles include carbon-based materials [graphite, non-graphitizable carbon, amorphous carbon, baked resin bodies (for example, carbonized by baking phenol resin and furan resin, etc.), cokes (for example, pitch coke, Needle coke and petroleum coke, etc.) and carbon fiber, etc.], silicon-based materials [silicon, silicon oxide (SiOx), silicon-carbon composites (carbon particles whose surface is coated with silicon and / or silicon carbide, silicon particles or silicon oxide particles coated with carbon and/or silicon carbide, silicon carbide, etc.) and silicon alloys (silicon-aluminum alloys, silicon-lithium alloys, silicon-nickel alloys, silicon-iron alloys, silicon-titanium alloys, silicon-manganese alloys, silicon-copper alloys and silicon-tin alloys, etc.], conductive polymers (e.g., polyacetylene and polypyrrole, etc.), metals (tin, aluminum, zirconium, titanium, etc.), metal oxides (titanium oxide and lithium-titanium oxides, etc.), metal alloys (eg, lithium-tin alloys, lithium-aluminum alloys, lithium-aluminum-manganese alloys, etc.), mixtures of these with carbonaceous materials, and the like.
These negative electrode active material particles may be used singly or in combination of two or more.

The volume average particle diameter of the negative electrode active material particles is preferably 0.01 to 100 μm, more preferably 0.1 to 20 μm, even more preferably 2 to 10 μm, from the viewpoint of the electrical characteristics of the battery.

At least part of the surface of the electrode active material particles is covered with a coating layer, and the coating layer contains particles made of a polymer having lithium ion conductivity, a coating resin, and a conductive aid.

(Particles made of polymer having lithium ion conductivity)
Particles made of polymers having lithium ion conductivity include, for example, polyethylene oxide (PEO), polyacrylonitrile (PAN), polyethylene glycol (PEG), polymethyl methacrylate (PMMA), LiPON, Li ₃ N, LixLa _{1- x} TiO ₃ (0<x<1) and particles made of polymers such as Li ₂ S--GeS--Ga ₂ S ₃ and the like.
Among them, polyethylene oxide (PEO), polyacrylonitrile ( PAN) and polyethylene glycol (PEG).

Particles made of a polymer having lithium ion conductivity preferably have a volume average particle diameter of 1 to 50 μm.
When the volume-average particle size of the particles made of the polymer having lithium ion conductivity is within the above range, the contact between the electrode active material particles and the electrolytic solution can be suitably suppressed.
The volume-average particle size of the particles made of the polymer having lithium ion conductivity is more preferably 5 to 40 μm.
As used herein, the term "volume average particle size" means a particle size at which the cumulative volume calculated from the small size side is 50% in the particle size distribution measured by the laser diffraction method.

Particles composed of a polymer having lithium ion conductivity may be adjusted to have the volume average particle diameter within the range described above by pulverizing, pulverizing, etc., and then classifying the particles.
The method of pulverization, pulverization, etc. is not particularly limited, and a known method (high-speed disper, bead mill, ball mill, etc.) can be appropriately selected and used.
The classification method is not particularly limited, and a known method such as using a multistage sieve can be appropriately selected and used.

The weight ratio of the polymer particles having lithium ion conductivity is preferably 0.1 to 5% by weight based on the weight of the coated electrode active material particles.
When the weight ratio of the particles made of the polymer having lithium ion conductivity is within the above range, contact between the electrode active material particles and the electrolytic solution can be suitably suppressed.
The weight ratio of the polymer particles having lithium ion conductivity is more preferably 0.5 to 4.5% by weight, more preferably 1.0 to 4.0% by weight, based on the weight of the coated electrode active material particles. % is more preferred.

(coating resin)
The coating resin is preferably, for example, a resin containing a polymer having the acrylic monomer (a) as an essential constituent monomer.
Specifically, the coating resin is preferably a polymer of a monomer composition containing acrylic acid (a0) as the acrylic monomer (a). In the monomer composition, from the viewpoint of flexibility of the coating layer, the content of acrylic acid (a0) is preferably 90% by weight or more and 95% by weight or less based on the weight of the entire monomer. .

The coating resin may contain, as the acrylic monomer (a), a monomer (a1) having a carboxyl group or an acid anhydride group other than acrylic acid (a0).

Examples of the monomer (a1) having a carboxyl group or an acid anhydride group other than acrylic acid (a0) include monocarboxylic acids having 3 to 15 carbon atoms such as methacrylic acid, crotonic acid and cinnamic acid; (anhydride) maleic acid and fumaric acid; acids, (anhydrous) itaconic acid, citraconic acid, mesaconic acid, and other dicarboxylic acids with 4 to 24 carbon atoms; trivalent to tetravalent or higher valent polycarboxylic acids with 6 to 24 carbon atoms, such as aconitic acid, etc. are mentioned.

The coating resin may contain a monomer (a2) represented by the following general formula (1) as the acrylic monomer (a).
_CH2 =C( ^R1 ) ^COOR2 (1)
[In formula (1), R ¹ is a hydrogen atom or a methyl group, and R ² is a linear or branched alkyl group having 4 to 12 carbon atoms or 3 to 36 carbon atoms. ]

In the monomer (a2) represented by the general formula (1), ^R1 represents a hydrogen atom or a methyl group. R ¹ is preferably a methyl group.
R ² is preferably a linear or branched alkyl group having 4 to 12 carbon atoms or a branched alkyl group having 13 to 36 carbon atoms.

(a21) Ester compounds in which R ² is a linear or branched alkyl group having 4 to 12 carbon atoms Examples of linear alkyl groups having 4 to 12 carbon atoms include butyl, pentyl, hexyl, heptyl, octyl, nonyl group, decyl group, undecyl group and dodecyl group.
Examples of branched alkyl groups having 4 to 12 carbon atoms include 1-methylpropyl group (sec-butyl group), 2-methylpropyl group, 1,1-dimethylethyl group (tert-butyl group), 1-methylbutyl group, 1 , 1-dimethylpropyl group, 1,2-dimethylpropyl group, 2,2-dimethylpropyl group (neopentyl group), 1-methylpentyl group, 2-methylpentyl group, 3-methylpentyl group, 4-methylpentyl group , 1,1-dimethylbutyl group, 1,2-dimethylbutyl group, 1,3-dimethylbutyl group, 2,2-dimethylbutyl group, 2,3-dimethylbutyl group, 1-ethylbutyl group, 2-ethylbutyl group , 1-methylhexyl group, 2-methylhexyl group, 2-methylhexyl group, 4-methylhexyl group, 5-methylhexyl group, 1-ethylpentyl group, 2-ethylpentyl group, 3-ethylpentyl group, 1 , 1-dimethylpentyl group, 1,2-dimethylpentyl group, 1,3-dimethylpentyl group, 2,2-dimethylpentyl group, 2,3-dimethylpentyl group, 2-ethylpentyl group, 1-methylheptyl group , 2-methylheptyl group, 3-methylheptyl group, 4-methylheptyl group, 5-methylheptyl group, 6-methylheptyl group, 1,1-dimethylhexyl group, 1,2-dimethylhexyl group, 1,3 -dimethylhexyl group, 1,4-dimethylhexyl group, 1,5-dimethylhexyl group, 1-ethylhexyl group, 2-ethylhexyl group, 1-methyloctyl group, 2-methyloctyl group, 3-methyloctyl group, 4 -methyloctyl group, 5-methyloctyl group, 6-methyloctyl group, 7-methyloctyl group, 1,1-dimethylheptyl group, 1,2-dimethylheptyl group, 1,3-dimethylheptyl group, 1,4 -dimethylheptyl group, 1,5-dimethylheptyl group, 1,6-dimethylheptyl group, 1-ethylheptyl group, 2-ethylheptyl group, 1-methylnonyl group, 2-methylnonyl group, 3-methylnonyl group, 4- methylnonyl group, 5-methylnonyl group, 6-methylnonyl group, 7-methylnonyl group, 8-methylnonyl group, 1,1-dimethyloctyl group, 1,2-dimethyloctyl group, 1,3-dimethyloctyl group, 1,4 -dimethyloctyl group, 1,5-dimethyloctyl group, 1,6-dimethyloctyl group, 1,7-dimethyloctyl group, 1-ethyloctyl group, 2-ethyloctyl group, 1-methyldecyl group, 2-methyldecyl group , 3-methy Rudecyl group, 4-methyldecyl group, 5-methyldecyl group, 6-methyldecyl group, 7-methyldecyl group, 8-methyldecyl group, 9-methyldecyl group, 1,1-dimethylnonyl group, 1,2-dimethylnonyl group, 1 ,3-dimethylnonyl group, 1,4-dimethylnonyl group, 1,5-dimethylnonyl group, 1,6-dimethylnonyl group, 1,7-dimethylnonyl group, 1,8-dimethylnonyl group, 1-ethylnonyl group, 2-ethylnonyl group, 1-methylundecyl group, 2-methylundecyl group, 3-methylundecyl group, 4-methylundecyl group, 5-methylundecyl group, 6-methylundecyl group, 7 -methylundecyl group, 8-methylundecyl group, 9-methylundecyl group, 10-methylundecyl group, 1,1-dimethyldecyl group, 1,2-dimethyldecyl group, 1,3-dimethyldecyl group , 1,4-dimethyldecyl group, 1,5-dimethyldecyl group, 1,6-dimethyldecyl group, 1,7-dimethyldecyl group, 1,8-dimethyldecyl group, 1,9-dimethyldecyl group, 1 -ethyldecyl group, 2-ethyldecyl group and the like. Among these, a 2-ethylhexyl group is particularly preferred.

(a22) Ester compound in which R ² is a branched alkyl group having 13 to 36 carbon atoms Examples of the branched alkyl group having 13 to 36 carbon atoms include 1-alkylalkyl groups [1-methyldodecyl group, 1-butyleicosyl group, 1-hexyloctadecyl group, 1-octylhexadecyl group, 1-decyltetradecyl group, 1-undecyltridecyl group, etc.], 2-alkylalkyl group [2-methyldodecyl group, 2-hexyloctadecyl group, 2- Octylhexadecyl group, 2-decyltetradecyl group, 2-undecyltridecyl group, 2-dodecylhexadecyl group, 2-tridecylpentadecyl group, 2-decyloctadecyl group, 2-tetradecyloctadecyl group, 2- hexadecyloctadecyl group, 2-tetradecyleicosyl group, 2-hexadecyleicosyl group, etc.], 3-34-alkylalkyl groups (3-alkylalkyl groups, 4-alkylalkyl groups, 5-alkylalkyl groups, 32 -alkylalkyl group, 33-alkylalkyl group and 34-alkylalkyl group, etc.), propylene oligomer (7 to 11-mer), ethylene/propylene (molar ratio 16/1 to 1/11) oligomer, isobutylene oligomer ( 7-8mers) and α-olefin (C5-20) oligomers (4-8mers) containing one or more branched alkyl groups such as residues obtained by removing hydroxyl groups from oxoalcohols. mixed alkyl group containing and the like.

The coating resin may contain an ester compound (a3) of a monohydric aliphatic alcohol having 1 to 3 carbon atoms and (meth)acrylic acid as the acrylic monomer (a).
Methanol, ethanol, 1-propanol, 2-propanol and the like can be mentioned as the monohydric aliphatic alcohol having 1 to 3 carbon atoms constituting the ester compound (a3).
(Meth)acrylic acid means acrylic acid or methacrylic acid.

The coating resin is preferably a polymer of a monomer composition containing acrylic acid (a0) and at least one of monomer (a1), monomer (a2) and ester compound (a3). It is more preferably a polymer of a monomer composition containing (a0) and at least one of a monomer (a1), an ester compound (a21) and an ester compound (a3), and acrylic acid (a0) and , the monomer (a1), the monomer (a2) and the ester compound (a3). ), ester compound (a21) and ester compound (a3).
Coating resins include, for example, a copolymer of acrylic acid and maleic acid using maleic acid as the monomer (a1), and acrylic acid and 2-ethylhexyl methacrylate using 2-ethylhexyl methacrylate as the monomer (a2). and a copolymer of acrylic acid and methyl methacrylate using methyl methacrylate as the ester compound (a3).

The total content of the monomer (a1), the monomer (a2) and the ester compound (a3) is 2.0 to 9.9 based on the total weight of the monomers, from the viewpoint of suppressing the volume change of the negative electrode active material particles. % by weight, more preferably 2.5 to 7.0% by weight.

It is preferable that the coating resin does not contain a salt (a4) of an anionic monomer having a polymerizable unsaturated double bond and an anionic group as the acrylic monomer (a).

Structures having polymerizable unsaturated double bonds include vinyl groups, allyl groups, styrenyl groups, and (meth)acryloyl groups.
Examples of anionic groups include sulfonic acid groups and carboxyl groups.
An anionic monomer having a polymerizable unsaturated double bond and an anionic group is a compound obtained by combining these, examples of which include vinylsulfonic acid, allylsulfonic acid, styrenesulfonic acid and (meth)acrylic acid. be done.
In addition, a (meth)acryloyl group means an acryloyl group or a methacryloyl group.
Examples of cations constituting the anionic monomer salt (a4) include lithium ions, sodium ions, potassium ions and ammonium ions.

In addition, the coating resin is a radically polymerizable resin that is copolymerizable with acrylic acid (a0), monomer (a1), monomer (a2), and ester compound (a3) as acrylic monomer (a) within a range that does not impair physical properties. It may contain a monomer (a5).
As the radically polymerizable monomer (a5), a monomer containing no active hydrogen is preferable, and the following monomers (a51) to (a58) can be used.

(a51) A hydroformed from a linear aliphatic monol having 13 to 20 carbon atoms, an alicyclic monool having 5 to 20 carbon atoms, or an araliphatic monool having 7 to 20 carbon atoms and (meth)acrylic acid Carvyl (meth)acrylate Examples of the monools include (i) linear aliphatic monools (tridecyl alcohol, myristyl alcohol, pentadecyl alcohol, cetyl alcohol, heptadecyl alcohol, stearyl alcohol, nonadecyl alcohol, arachidyl alcohol etc.), (ii) alicyclic monools (cyclopentyl alcohol, cyclohexyl alcohol, cycloheptyl alcohol, cyclooctyl alcohol, etc.), (iii) araliphatic monools (benzyl alcohol, etc.) and mixtures of two or more thereof mentioned.

(a52) poly (n = 2-30) oxyalkylene (2-4 carbon atoms) alkyl (1-18 carbon atoms) ether (meth) acrylate [ethylene oxide of methanol (hereinafter abbreviated as EO) 10 mol adduct (meth ) acrylate, methanol propylene oxide (hereinafter abbreviated as PO) 10 mol adduct (meth)acrylate, etc.]

(a53) Nitrogen-containing vinyl compound (a53-1) Amido group-containing vinyl compound (i) (meth)acrylamide compounds having 3 to 30 carbon atoms, such as N,N-dialkyl (1 to 6 carbon atoms) or dialkyl (carbon atoms) 7-15) (meth)acrylamide (N,N-dimethylacrylamide, N,N-dibenzylacrylamide, etc.), diacetoneacrylamide (ii) amide group containing 4 to 20 carbon atoms, excluding the above (meth)acrylamide compounds Vinyl compounds such as N-methyl-N-vinylacetamide, cyclic amides [pyrrolidone compounds (C6-C13, such as N-vinylpyrrolidone, etc.)]

(a53-2) (meth)acrylate compound (i) dialkyl (1 to 4 carbon atoms) aminoalkyl (1 to 4 carbon atoms) (meth)acrylate [N,N-dimethylaminoethyl (meth)acrylate, N,N -Diethylaminoethyl (meth)acrylate, t-butylaminoethyl (meth)acrylate, morpholinoethyl (meth)acrylate, etc.]
(ii) quaternary ammonium group-containing (meth)acrylate {tertiary amino group-containing (meth)acrylate [N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, etc.] compounds (those quaternized using a quaternizing agent such as methyl chloride, dimethyl sulfate, benzyl chloride, and dimethyl carbonate), etc.}

(a53-3) Heterocycle-containing vinyl compounds pyridine compounds (having 7 to 14 carbon atoms, such as 2- or 4-vinylpyridine), imidazole compounds (having 5 to 12 carbon atoms, such as N-vinylimidazole), pyrrole compounds (having carbon atoms 6-13, such as N-vinylpyrrole), pyrrolidone compounds (C6-13, such as N-vinyl-2-pyrrolidone)

(a53-4) Nitrile group-containing vinyl compounds Nitrile group-containing vinyl compounds having 3 to 15 carbon atoms, such as (meth)acrylonitrile, cyanostyrene, cyanoalkyl (1 to 4 carbon atoms) acrylates

(a53-5) Other nitrogen-containing vinyl compounds Nitro group-containing vinyl compounds (carbon number 8-16, such as nitrostyrene), etc.

(a54) vinyl hydrocarbon (a54-1) aliphatic vinyl hydrocarbon having 2 to 18 or more carbon atoms (ethylene, propylene, butene, isobutylene, pentene, heptene, diisobutylene, octene, dodecene, octadecene, etc.), Dienes having 4 to 10 or more carbon atoms (butadiene, isoprene, 1,4-pentadiene, 1,5-hexadiene, 1,7-octadiene, etc.), etc.

(a54-2) cyclic unsaturated compounds having 4 to 18 or more alicyclic vinyl hydrocarbon carbon atoms, such as cycloalkene (e.g. cyclohexene), (di)cycloalkadiene [e.g. (di)cyclopentadiene], terpene ( e.g. pinene and limonene), indene

(a54-3) Aromatic unsaturated compounds having 8 to 20 or more aromatic vinyl hydrocarbon carbon atoms, such as styrene, α-methylstyrene, vinyltoluene, 2,4-dimethylstyrene, ethylstyrene, isopropylstyrene, butyl Styrene, phenylstyrene, cyclohexylstyrene, benzylstyrene

(a55) vinyl esters aliphatic vinyl esters [having 4 to 15 carbon atoms, e.g. alkenyl esters of aliphatic carboxylic acids (mono- or dicarboxylic acids) (e.g. vinyl acetate, vinyl propionate, vinyl butyrate, diallyl adipate, isopropenyl acetate, vinyl methoxy acetate)]
Aromatic vinyl esters [C 9-20, e.g. alkenyl esters of aromatic carboxylic acids (mono- or dicarboxylic acids) (e.g. vinyl benzoate, diallyl phthalate, methyl-4-vinyl benzoate), aromatic ring-containing aliphatic carboxylic acids ester (e.g. acetoxystyrene)]

(a56) Vinyl ether Aliphatic vinyl ether [C3-C15, such as vinyl alkyl (C1-10) ether (vinyl methyl ether, vinyl butyl ether, vinyl 2-ethylhexyl ether, etc.), vinyl alkoxy (C1-6) Alkyl (C 1-4) ethers (vinyl-2-methoxyethyl ether, methoxybutadiene, 3,4-dihydro-1,2-pyran, 2-butoxy-2'-vinyloxydiethyl ether, vinyl-2-ethyl mercaptoethyl ether, etc.), poly(2-4)(meth)allyloxyalkanes (having 2-6 carbon atoms) (diallyloxyethane, triaryloxyethane, tetraallyloxybutane, tetramethallyloxyethane, etc.)], Aromatic vinyl ethers (8-20 carbon atoms, eg vinyl phenyl ether, phenoxystyrene)

(a57) vinyl ketones aliphatic vinyl ketones (4-25 carbon atoms, eg vinyl methyl ketone, vinyl ethyl ketone), aromatic vinyl ketones (9-21 carbon atoms, eg vinyl phenyl ketone)

(a58) Unsaturated dicarboxylic acid diester Unsaturated dicarboxylic acid diester having 4 to 34 carbon atoms, such as dialkyl fumarate (the two alkyl groups are linear, branched or alicyclic groups having 1 to 22 carbon atoms) ), dialkyl maleates (wherein the two alkyl groups are linear, branched or alicyclic groups having 1 to 22 carbon atoms)

When the radically polymerizable monomer (a5) is contained, its content is preferably 0.1 to 3.0% by weight based on the total weight of the monomers.

A preferable lower limit of the weight average molecular weight of the coating resin is 3,000, a more preferable lower limit is 5,000, and a further preferable lower limit is 7,000. On the other hand, the preferred upper limit of the weight average molecular weight of the coating resin is 100,000, and the more preferred upper limit is 70,000.

The weight average molecular weight of the coating resin can be determined by gel permeation chromatography (hereinafter abbreviated as GPC) measurement under the following conditions.
Apparatus: Alliance GPC V2000 (manufactured by Waters)
Solvents: ortho-dichlorobenzene, DMF, THF
Standard substance: polystyrene sample concentration: 3 mg/ml
Column stationary phase: PLgel 10 μm, MIXED-B 2 in series (manufactured by Polymer Laboratories)
Column temperature: 135°C

The coating resin is a known polymerization initiator {azo initiator [2,2′-azobis(2-methylpropionitrile), 2,2′-azobis(2,4-dimethylvaleronitrile), 2,2′ -azobis (2-methylbutyronitrile), etc.], peroxide-based initiators (benzoyl peroxide, di-t-butyl peroxide, lauryl peroxide, etc.) etc.} using known polymerization methods (bulk polymerization, solution polymerization, emulsion polymerization, suspension polymerization, etc.).
The amount of the polymerization initiator used is preferably 0.01 to 5% by weight, more preferably 0.05 to 2% by weight, based on the total weight of the monomers, from the viewpoint of adjusting the weight average molecular weight to a preferred range. It is more preferably 0.1 to 1.5% by weight, and the polymerization temperature and polymerization time are adjusted according to the type of polymerization initiator. 30 to 120° C.), and the reaction time is preferably 0.1 to 50 hours (more preferably 2 to 24 hours).

Examples of solvents used in solution polymerization include esters (having 2 to 8 carbon atoms, such as ethyl acetate and butyl acetate), alcohols (having 1 to 8 carbon atoms, such as methanol, ethanol and octanol), hydrocarbons (having 4 to 8, such as n-butane, cyclohexane and toluene), amides (such as N,N-dimethylformamide (hereinafter abbreviated as DMF)) and ketones (having 3 to 9 carbon atoms, such as methyl ethyl ketone), and the weight average From the viewpoint of adjusting the molecular weight to a preferred range, the amount used is preferably 5 to 900% by weight, more preferably 10 to 400% by weight, and still more preferably 30 to 300% by weight, based on the total weight of the monomers. , the monomer concentration is preferably 10 to 95% by weight, more preferably 20 to 90% by weight, and still more preferably 30 to 80% by weight.

Dispersion media in emulsion polymerization and suspension polymerization include water, alcohols (eg, ethanol), esters (eg, ethyl propionate), light naphtha, etc. Emulsifiers include higher fatty acid (C10-24) metal salts. (e.g. sodium oleate and sodium stearate), higher alcohol (C10-24) sulfate metal salt (e.g. sodium lauryl sulfate), ethoxylated tetramethyldecyndiol, sodium sulfoethyl methacrylate, dimethylaminomethyl methacrylate, etc. is mentioned. Furthermore, polyvinyl alcohol, polyvinylpyrrolidone, etc. may be added as a stabilizer.
The monomer concentration of the solution or dispersion is preferably 5 to 95% by weight, more preferably 10 to 90% by weight, still more preferably 15 to 85% by weight, and the amount of the polymerization initiator used is based on the total weight of the monomers. is preferably 0.01 to 5% by weight, more preferably 0.05 to 2% by weight.
In the polymerization, known chain transfer agents such as mercapto compounds (dodecyl mercaptan, n-butyl mercaptan, etc.) and/or halogenated hydrocarbons (carbon tetrachloride, carbon tetrabromide, benzyl chloride, etc.) can be used. .

The coating resin is a cross-linking agent (A') {preferably a polyepoxy compound (a'1) [polyglycidyl ether (bisphenol A diglycidyl ether, propylene glycol di glycidyl ether and glycerin triglycidyl ether, etc.) and polyglycidylamines (N,N-diglycidylaniline and 1,3-bis (N,N-diglycidylaminomethyl), etc.)] and/or polyol compounds (a'2) (ethylene glycol or the like)} may be a crosslinked polymer.

Examples of the method of cross-linking the coating resin using the cross-linking agent (A′) include a method of coating the negative electrode active material particles with the coating resin and then cross-linking the particles. Specifically, a resin solution containing the negative electrode active material particles and the coating resin is mixed and the solvent is removed to produce the coated active material particles, and then a solution containing the cross-linking agent (A′) is applied to the coated active material particles. A method of mixing and heating to cause desolvation and a cross-linking reaction to cause a cross-linking reaction of the coating resin with the cross-linking agent (A') on the surface of the negative electrode active material particles can be exemplified.
The heating temperature is adjusted according to the type of cross-linking agent, and is preferably 70° C. or higher when using the polyepoxy compound (a′1) as the cross-linking agent, and when using the polyol compound (a′2) It is preferably 120° C. or higher.

(Conductivity aid)
The conductive aid is preferably selected from materials having conductivity.
Preferable conductive aids include metals [aluminum, stainless steel (SUS), silver, gold, copper, titanium, etc.], carbon [graphite and carbon black (acetylene black, ketjen black, furnace black, channel black, thermal lamp black, carbon nanofibers, etc.), and mixtures thereof.
One of these conductive aids may be used alone, or two or more thereof may be used in combination. Moreover, these alloys or metal oxides may be used.
Among them, from the viewpoint of electrical stability, aluminum, stainless steel, carbon, silver, gold, copper, titanium and mixtures thereof are more preferable, silver, gold, aluminum, stainless steel and carbon are more preferable, and particularly Carbon is preferred.
These conductive aids may also be those obtained by coating a conductive material [preferably a metal one of the above-described conductive aids] around a particulate ceramic material or a resin material by plating or the like.

The shape (form) of the conductive aid is not limited to a particle form, and may be in a form other than a particle form, such as carbon nanofibers, carbon nanotubes, etc., which are practically used as so-called filler-type conductive aids. may

Although the average particle size of the conductive aid is not particularly limited, it is preferably about 0.01 to 10 μm from the viewpoint of the electrical characteristics of the battery.
In the present specification, the "particle diameter of the conductive aid" means the maximum distance L among the distances between arbitrary two points on the outline of the conductive aid. The value of "average particle size" is the average value of the particle size of particles observed in several to several tens of fields of view using an observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). The calculated value shall be adopted.

The ratio of the coating resin and the conductive aid is not particularly limited, but from the viewpoint of the internal resistance of the battery, etc., the weight ratio of the coating resin (resin solid content weight): conductive aid is 1:0.01 to 1. :50, more preferably 1:0.2 to 1:3.0.

<Method for producing coated electrode active material particles for lithium ion battery>
In the method for producing coated electrode active material particles for a lithium ion battery of the present invention, the electrode active material particles, the polymer particles having lithium ion conductivity, the coating resin, the conductive aid, and the organic solvent are mixed, and then the solvent is removed. have a process.

The organic solvent is not particularly limited as long as it is an organic solvent capable of dissolving the coating resin, and a known organic solvent can be appropriately selected and used.

In the method for producing coated electrode active material particles for lithium ion batteries of the present invention, first, electrode active material particles, polymer particles having lithium ion conductivity, a coating resin, and a conductive aid are mixed in an organic solvent.
The order of mixing the electrode active material particles, the particles made of a polymer having lithium ion conductivity, the coating resin and the conductive aid is not particularly limited, and for example, the previously mixed coating resin, the polymer having lithium ion conductivity A resin composition comprising particles and a conductive aid may be further mixed with the electrode active material particles, or the electrode active material particles, particles made of a polymer having lithium ion conductivity, and a conductive aid may be mixed at the same time. Alternatively, the electrode active material particles may be mixed with a coating resin, and further mixed with polymer particles having lithium ion conductivity and a conductive aid.

The coated electrode active material particles for a lithium ion battery of the present invention are obtained by coating the electrode active material particles with a coating layer containing a coating resin, particles made of a polymer having lithium ion conductivity, and a conductive aid. For example, the electrode active material particles are placed in a universal mixer and stirred at 30 to 500 rpm, and the resin solution containing the coating resin is dropped and mixed over 1 to 90 minutes to obtain a polymer having lithium ion conductivity. It can be obtained by mixing particles and a conductive aid, heating to 50 to 200 ° C. while stirring, reducing the pressure to 0.007 to 0.04 MPa, holding for 10 to 150 minutes, and removing the solvent. .

The mixing ratio of the electrode active material particles and the resin composition containing the polymer particles having lithium ion conductivity, the coating resin, and the conductive aid is not particularly limited, but the weight ratio of the electrode active material particles : The resin composition is preferably 1:0.001 to 0.1.

From the viewpoint of cycle characteristics, the coverage of the coated electrode active material particles for a lithium ion battery of the present invention is preferably 30 to 95% obtained by the following formula.
Coverage (%) = {1-[BET specific surface area of coated active material particles/(BET specific surface area of electrode active material x weight ratio of electrode active material contained in coated electrode active material particles + having lithium ion conductivity BET specific surface area of polymer x weight ratio of polymer having lithium ion conductivity contained in coated electrode active material particles + BET specific surface area of conductive aid x weight of conductive aid contained in coated electrode active material particles ratio)]}×100

<Electrodes for lithium-ion batteries>
The lithium ion battery electrode of the present invention is a lithium ion battery electrode comprising an electrode active material layer containing the coated electrode active material particles for a lithium ion battery of the present invention and an electrolytic solution containing an electrolyte and a solvent, The weight ratio of the coating resin contained in the lithium ion battery electrode is 1 to 10% by weight based on the weight of the lithium ion battery electrode.

(Electrode active material layer)
The lithium ion battery electrode of the present invention comprises an electrode active material layer containing the coated electrode active material particles for a lithium ion battery of the present invention and an electrolytic solution containing an electrolyte and a solvent.

The coated electrode active material particles for lithium ion batteries include coated positive electrode active material particles and coated negative electrode active material particles, and can be appropriately selected depending on whether it is used for the positive electrode or the negative electrode.

From the viewpoint of the moldability, mechanical strength and energy density of the lithium ion battery electrode, the coated electrode active material particles for the lithium ion battery should have a weight ratio of the coating resin contained in the lithium ion battery electrode that is equal to that of the lithium ion battery electrode. It is preferably contained in an amount of 1 to 10% by weight based on the weight.
When the coated electrode active material particles for lithium ion batteries are coated positive electrode active material particles for lithium ion batteries, the weight ratio of the coating resin contained in the positive electrode for lithium ion batteries is 1 based on the weight of the positive electrode for lithium ion batteries. More preferably, it is contained in an amount of up to 5% by weight.
Further, when the coated electrode active material particles for lithium ion batteries are coated negative electrode active material particles for lithium ion batteries, the weight ratio of the coating resin contained in the negative electrode for lithium ion batteries is based on the weight of the negative electrode for lithium ion batteries. It is more preferable that it is contained so as to be 5 to 10% by weight.

_As the _electrolyte , _{electrolytes used} in _{known electrolytic solutions} can be used. Lithium salts of organic anions such as (CF ₃ SO ₂ ) ₂ , LiN(C ₂ F ₅ SO ₂ ) ₂ and LiC(CF ₃ SO ₂ ) ₃ are included. Among these, LiN(FSO ₂ ) ₂ is preferable from the viewpoint of battery output and charge/discharge cycle characteristics.

As the solvent, non-aqueous solvents used in known electrolytic solutions can be used. , amide compounds, sulfones, sulfolane and mixtures thereof can be used.

Examples of lactone compounds include 5-membered ring (γ-butyrolactone, γ-valerolactone, etc.) and 6-membered ring (δ-valerolactone, etc.) lactone compounds.

Cyclic carbonates include propylene carbonate, ethylene carbonate (EC) and butylene carbonate (BC).
Chain carbonates include dimethyl carbonate (DMC), methyl ethyl carbonate (MEC), diethyl carbonate (DEC), methyl-n-propyl carbonate, ethyl-n-propyl carbonate and di-n-propyl carbonate. .

Chain carboxylic acid esters include methyl acetate, ethyl acetate, propyl acetate and methyl propionate.

Cyclic ethers include tetrahydrofuran, tetrahydropyran, 1,3-dioxolane and 1,4-dioxane. Chain ethers include dimethoxymethane and 1,2-dimethoxyethane.

Phosphate esters include trimethyl phosphate, triethyl phosphate, ethyldimethyl phosphate, diethylmethyl phosphate, tripropyl phosphate, tributyl phosphate, tri(trifluoromethyl) phosphate, tri(trichloromethyl) phosphate, Tri(trifluoroethyl) phosphate, tri(triperfluoroethyl) phosphate, 2-ethoxy-1,3,2-dioxaphospholan-2-one, 2-trifluoroethoxy-1,3,2- dioxaphospholan-2-one, 2-methoxyethoxy-1,3,2-dioxaphospholan-2-one and the like.

Acetonitrile etc. are mentioned as a nitrile compound. DMF etc. are mentioned as an amide compound. Sulfones include dimethylsulfone, diethylsulfone, and the like.

One of these solvents may be used alone, or two or more thereof may be used in combination.

The concentration of the electrolyte in the electrolytic solution is preferably 1.2 to 5.0 mol/L, more preferably 1.5 to 4.5 mol/L, and 1.8 to 4.0 mol/L. more preferably 2.0 to 3.5 mol/L.

The electrode active material layer may further contain a conductive aid in addition to the conductive aid contained in the coating layer of the coated electrode active material particles described above. The conductive additive contained in the coating layer is integrated with the coated electrode active material particles, whereas the conductive additive contained in the electrode active material layer is contained separately from the coated electrode active material particles.
As the conductive aid that the electrode active material layer may contain, those described in <Coated Electrode Active Material Particles for Lithium Ion Battery> can be used.

The electrode active material layer preferably does not contain a binder.
In this specification, the binder means an agent that cannot reversibly fix the coated electrode active material particles to each other and the coated electrode active material particles to the current collector, and includes starch, polyvinylidene fluoride, Known solvent-drying type binders for lithium ion batteries such as polyvinyl alcohol, carboxymethylcellulose, polyvinylpyrrolidone, tetrafluoroethylene, styrene-butadiene rubber, polyethylene and polypropylene are included.
These binders are used by being dissolved or dispersed in a solvent, and are solidified by volatilizing and distilling off the solvent to irreversibly bind the coated electrode active material particles together and the coated electrode active material particles and the current collector. is fixed to

The electrode active material layer may contain an adhesive resin.
The tacky resin means a resin that does not solidify and has tackiness even when the solvent component is volatilized and dried, and is a material different from the binder.
Further, while the coating layer constituting the coated electrode active material particles is fixed to the surfaces of the electrode active material particles, the adhesive resin reversibly fixes the surfaces of the electrode active material particles to each other. The adhesive resin can be easily separated from the surface of the electrode active material particles, but the coating layer cannot be easily separated. Therefore, the coating layer and the adhesive resin are different materials.

The adhesive resin contains at least one low Tg monomer selected from the group consisting of vinyl acetate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, butyl acrylate and butyl methacrylate as an essential constituent monomer. is 45% by weight or more based on the total weight of the constituent monomers.
When the adhesive resin is used, it is preferable to use 0.01 to 10% by weight of the adhesive resin with respect to the total weight of the electrode active material particles.

From the viewpoint of battery performance, the thickness of the electrode active material layer is preferably 150 to 600 μm, more preferably 200 to 450 μm.

(current collector)
It is preferable that the lithium ion battery electrode includes a current collector, and an electrode active material layer is provided on the surface of the current collector.

Materials constituting the current collector include metallic materials such as copper, aluminum, titanium, stainless steel, nickel, and alloys thereof, as well as calcined carbon, conductive polymer materials, conductive glass, and the like.
The shape of the current collector is not particularly limited, and may be a sheet-like current collector made of the above material or a deposited layer made of fine particles made of the above material.

The lithium-ion battery electrode of the present invention preferably includes a resin current collector made of a conductive polymer material, and an electrode active material layer is provided on the surface of the resin current collector.

As the conductive polymer material constituting the resin current collector, for example, a resin to which a conductive material is added can be used.
As the conductive material that constitutes the conductive polymer material, the same material as the conductive aid contained in the coating layer can be preferably used.

Examples of resins constituting the conductive polymer material include polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), polycycloolefin (PCO), polyethylene terephthalate (PET), polyethernitrile (PEN), poly Tetrafluoroethylene (PTFE), styrene butadiene rubber (SBR), polyacrylonitrile (PAN), polymethyl acrylate (PMA), polymethyl methacrylate (PMMA), polyvinylidene fluoride (PVdF), epoxy resin, silicone resin or mixtures thereof etc.
From the viewpoint of electrical stability, polyethylene (PE), polypropylene (PP), polymethylpentene (PMP) and polycycloolefin (PCO) are preferred, and polyethylene (PE), polypropylene (PP) and polymethylpentene are more preferred. (PMP).
The resin current collector can be obtained by known methods described in JP-A-2012-150905, WO 2015/005116, and the like.

Although the thickness of the current collector is not particularly limited, it is preferably 5 to 150 μm.

(Method for producing electrode for lithium ion battery)
The lithium ion battery electrode of the present invention is, for example, a slurry for an electrode active material layer containing the coated electrode active material particles for a lithium ion battery of the present invention, an electrolytic solution containing an electrolyte and a solvent, and optionally a conductive aid and the like. can be prepared by applying to a current collector and then drying. Specifically, the slurry for the electrode active material layer is coated on the current collector with a coating device such as a bar coater, and then the nonwoven fabric is left standing on the electrode active material particles to absorb the solvent. A method of removing and, if necessary, pressing with a press machine, and the like can be mentioned.
Alternatively, for example, a powder (electrode precursor) obtained by mixing the coated electrode active material particles for a lithium ion battery of the present invention and, if necessary, a conductive agent or the like is applied to a current collector and pressed with a press to activate the electrode. It can also be produced by injecting an electrolytic solution after forming a material layer.
Alternatively, the slurry for the electrode active material layer or the electrode precursor is applied onto a release film and pressed to form an electrode active material layer, the electrode active material layer is transferred to a current collector, and then an electrolytic solution is injected. You may

<Lithium-ion battery>
The lithium ion battery electrode of the present invention can be used as a lithium ion battery by combining a separator with an electrode paired with the lithium ion battery electrode of the present invention.
As the electrode paired with the lithium ion battery electrode of the present invention, a known electrode can be used, but the lithium ion battery electrode of the present invention is preferred.

Separators include porous films made of polyethylene or polypropylene, laminated films of porous polyethylene film and porous polypropylene, non-woven fabrics made of synthetic fibers (polyester fibers, aramid fibers, etc.) or glass fibers, and silica on their surfaces. , alumina, titania, and other known separators for lithium ion batteries.

A lithium ion battery is produced by, for example, stacking the lithium ion battery electrode of the present invention, a separator, and an electrode paired with the lithium ion battery electrode of the present invention in this order, and then, if necessary, injecting an electrolytic solution. can be manufactured.

EXAMPLES Next, the present invention will be specifically described with reference to Examples, but the present invention is not limited to Examples unless it departs from the gist of the present invention. Unless otherwise specified, parts means parts by weight and % means % by weight.

<Particles made of polymer having lithium ion conductivity>
The following materials were prepared as particles composed of a polymer having lithium ion conductivity.
Polyethylene glycol (PEG): PEG-6000P (manufactured by Sanyo Chemical Industries, Ltd.), volume average particle size 106 μm
Polyacrylonitrile (PAN): Polyacrylonitrile powder (manufactured by Goodfellow), volume average particle size 50 μm
Polyethylene oxide (PEO): Alcox (manufactured by Meisei Chemical Industry Co., Ltd.), volume average particle size 1000 μm

Materials prepared as particles of a polymer having lithium ion conductivity were placed in disposable cups, and pulverized together with zirconia pulverizing balls with an Awatori Mixer at 1000 rpm for 10 sec. After that, the mixture was allowed to cool, and was pulverized again with a mixer at 1000 rpm for 10 seconds. This was repeated 6 times, and the pulverized materials obtained were each classified with a sieve having an opening of 50 μm.
Each material after classification was used in the following examples as particles composed of a polymer having lithium ion conductivity.
Table 1 or 2 shows the volume-average particle size after pulverization and classification of particles composed of a polymer having lithium ion conductivity used in Examples.

<Particles made of polymer not having lithium ion conductivity>
The following materials were prepared as particles composed of a polymer having no lithium ion conductivity.
(polyester resin)
673 parts of 2 mol bisphenol A propylene oxide adduct, 15 parts of 5 mol propylene oxide adduct of phenolic novolac resin (about 5 nuclei), terephthalic 157 parts of acid, 37 parts of maleic anhydride, 152 parts of dodecenylsuccinic anhydride and 2 parts of dibutyltin oxide were added and reacted under normal pressure at 220° C. for 8 hours, and further reacted under reduced pressure of 0.001 to 0.002 MPa for 5 hours. . Next, 32 parts of trimellitic anhydride was added to this and reacted at 180° C. under normal pressure for 2 hours to obtain a polyester resin.
The obtained polyester resin was cut into pieces of about 1 cm×1 cm with scissors and pulverized with a tablet crusher for 5 minutes.
The obtained powder was placed in a disposable cup and pulverized together with a zirconia pulverizing ball with an Awatori Mixer at 1000 rpm for 10 sec. After that, the mixture was allowed to cool, and was pulverized again with a mixer at 1000 rpm for 10 seconds. This was repeated 6 times, and the pulverized materials obtained were each classified with a sieve having an opening of 50 μm.
(polyacrylic acid)
Polyacrylic acid [product name: Polyacrylic acid 5000, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.] was placed in a disposable cup and crushed together with zirconia crushing balls with an Awatori Mixer at 1000 rpm for 10 sec. After that, the mixture was allowed to cool, and was pulverized again with a mixer at 1000 rpm for 10 seconds. This was repeated 6 times, and the pulverized materials obtained were each classified with a sieve having an opening of 50 μm.
The classified material was used in the following comparative examples as particles composed of a polymer having no lithium ion conductivity.
Table 1 or 2 shows the volume-average particle size after pulverization and classification of the polymer particles having no lithium ion conductivity used in Comparative Examples.

<Production of coating resin>
65 parts of toluene was charged into a four-neck Kolben equipped with a stirrer, thermometer, reflux condenser, dropping funnel and nitrogen gas introduction tube, and the temperature was raised to 75°C. Next, a monomer mixture containing 80 parts of lauryl methacrylate, 15 parts of methyl methacrylate, 4.6 parts of methacrylic acid and 0.4 parts of 1,6-hexanediol dimethacrylate, and 2,2′-azobis(2,4- Dimethylvaleronitrile) was dissolved in 5 parts of toluene, and an initiator solution was continuously added dropwise over 2 hours with a dropping funnel under stirring while blowing nitrogen into a four-neck Kolben to initiate radical polymerization. went. After the dropwise addition was completed, the temperature was raised to 75° C. and the reaction was continued for 1 hour.
Next, an initiator solution prepared by dissolving 0.01 part of 2,2′-azobis(2,4-dimethylvaleronitrile) in 1 part of toluene was added through a dropping funnel, and the reaction was continued for 3 hours to obtain a copolymer solution. Obtained. The resulting copolymer solution was transferred to a Teflon vat. Toluene was distilled off by vacuum drying at 80° C. and 0.09 MPa for 3 hours. Then, the temperature was raised to 100° C. for 1 hour, and further heated at 120° C. and 0.01 MPa for 1 hour in a vacuum dryer to prepare a coating resin.

(Example 1)
<Production of coated positive electrode active material particles for lithium ion batteries>
One part of the coating resin was dissolved in 3 parts of toluene to obtain a coating resin solution.
92 parts of positive electrode active material particles (LiNi _0.8 Co _0.15 Al _0.05 O ₂ powder, volume average particle size 4 μm) were placed in a universal mixer high speed mixer FS25 [manufactured by Earth Technica Co., Ltd.], room temperature, While being stirred at 720 rpm, 12 parts of the coating resin solution was added dropwise over 2 minutes and further stirred for 5 minutes.
Then, while stirring, 3 parts of acetylene black [Denka Black (registered trademark) manufactured by Denka Co., Ltd.], which is a conductive agent, and particles made of a polymer having lithium ion conductivity (trade name “PEG-6000P” [Sanyo Kasei Kogyo Co., Ltd.]) (1% by weight based on the weight of the coated positive electrode active material particles) was added in divided portions over 2 minutes, and stirring was continued for 30 minutes.
Thereafter, the pressure was reduced to 0.01 MPa while maintaining stirring, then the temperature was raised to 120°C while stirring and the degree of pressure reduction were maintained, and the volatile matter was distilled off while maintaining the stirring, degree of pressure reduction and temperature for 8 hours. .
The obtained powder was classified with a sieve having an opening of 200 μm to prepare coated positive electrode active material particles.

<Preparation of electrolytic solution>
An electrolytic solution was prepared by dissolving LiN(FSO ₂ ) ₂ at a ratio of 2.0 mol/L in a mixed solvent of ethylene carbonate (EC) and propylene carbonate (PC) (volume ratio 1:1).

<Preparation of resin current collector>
Using a twin-screw extruder, 70 parts of polypropylene [trade name “SunAllomer PL500A”, manufactured by SunAllomer Co., Ltd.], 25 parts of carbon nanotubes [trade name: “FloTube9000”, manufactured by CNano] and a dispersant [trade name “Umex 1001” , manufactured by Sanyo Chemical Industries, Ltd.] were melt-kneaded at 200° C. and 200 rpm to obtain a resin mixture.
The resulting resin mixture was passed through a T-die extrusion film forming machine and stretch-rolled to obtain a conductive film for a resin current collector having a thickness of 100 μm.
Next, the obtained conductive film for a resin current collector was cut into a size of 4.0 cm×3.0 cm, nickel vapor deposition was applied to one side, and a terminal (5 mm×3 cm) for current extraction was connected. A resin current collector was produced.

<Preparation of positive electrode for lithium ion battery>
34 parts of the electrolytic solution and 66 parts of the above-described coated positive electrode active material particles were mixed for 5 minutes at 2000 rpm using a planetary stirring type mixing and kneading device {Awatori Mixer [manufactured by Thinky Co., Ltd.] to obtain a slurry for a positive electrode active material layer. was made. The obtained positive electrode active material layer slurry was applied to one side of the resin current collector so that the basis weight was 111 mg/cm ² and pressed at a pressure of 62 MPa for about 10 seconds to obtain a lithium ion battery having a thickness of 450 μm. A positive electrode (15φ) was produced.
The weight ratio of the coating resin in the prepared positive electrode for lithium ion batteries was 3% by weight based on the weight of the positive electrode for lithium ion batteries.

<Production of lithium ion battery>
The prepared positive electrode for a lithium ion battery was combined with a Li metal counter electrode via a separator (#3501 manufactured by Celgard) to prepare a laminate cell.

(Examples 2-9, Comparative Examples 1-3)
Coated positive electrode active material particles were produced in the same manner as in Example 1, except that the type and amount of particles made of a polymer having lithium ion conductivity were changed as shown in Table 1.
Thereafter, a positive electrode for a lithium ion battery and a lithium ion battery were produced in the same manner as in Example 1, except that the coated positive electrode active material particles thus produced were used.
In Comparative Examples 2 and 3, a polyester resin was used as the polymer having no lithium ion conductivity instead of the polymer having lithium ion conductivity. As shown in the "type of polymer" column in Table 1, this polyester resin is a polymer that does not have lithium ion conductivity.

<Production of coated negative electrode active material particles for lithium ion batteries>
(Example 10)
One part of the coating resin was dissolved in 3 parts of toluene to obtain a coating resin solution.
80 parts of negative electrode active material particles (hard carbon powder, volume average particle diameter 25 μm) are placed in a universal mixer High Speed Mixer FS25 [manufactured by Earth Technica Co., Ltd.], and stirred at room temperature and 720 rpm, 32 parts of a coating resin solution. was added dropwise over 2 minutes, and the mixture was further stirred for 5 minutes.
Next, in a stirred state, 10 parts of acetylene black [Denka Black (registered trademark) manufactured by Denka Co., Ltd.], 1 part of carbon nanofiber [manufactured by Teijin Co., Ltd.], and a polymer having lithium ion conductivity, which are conductive additives. Particles consisting of (trade name “PEG-6000P” [manufactured by Sanyo Chemical Industries, Ltd.]) 1 part (1% by weight based on the weight of the coated negative electrode active material particles) are charged in 2 minutes while being divided, and stirred for 30 minutes. Continued.
Thereafter, the pressure was reduced to 0.01 MPa while maintaining stirring, then the temperature was raised to 140°C while stirring and the degree of pressure reduction were maintained, and the volatile matter was distilled off while maintaining the stirring, the degree of pressure reduction, and the temperature for 8 hours. .
The obtained powder was classified with a sieve having an opening of 200 μm to prepare coated negative electrode active material particles.

<Production of negative electrode for lithium ion battery>
49 parts of the electrolytic solution and 51 parts of the coated negative electrode active material particles were mixed for 5 minutes at 2000 rpm using a planetary stirring type mixing and kneading device {Awatori Mixer [manufactured by Thinky Co., Ltd.] to obtain a slurry for the negative electrode active material layer. was made. The obtained negative electrode active material layer slurry was applied to one side of the resin current collector so that the basis weight was 59 mg/cm ² and pressed at a pressure of 14 MPa for about 10 seconds to obtain a lithium ion battery having a thickness of 600 μm. A negative electrode (16φ) was prepared.
The weight ratio of the coating resin in the produced negative electrode for lithium ion batteries was 8% by weight based on the weight of the negative electrode for lithium ion batteries.

<Production of lithium ion battery>
The prepared negative electrode for lithium ion battery was combined with a Cu metal counter electrode via a separator (#3501 manufactured by Celgard) to prepare a laminate cell.

(Examples 11-18, Comparative Examples 4-6)
Coated positive electrode active material particles were produced in the same manner as in Example 10, except that the type and amount of particles made of a polymer having lithium ion conductivity were changed as shown in Table 2.
Thereafter, a negative electrode for a lithium ion battery and a lithium ion battery were produced in the same manner as in Example 10, except that the coated negative electrode active material particles thus produced were used.
In Comparative Examples 5 and 6, polyacrylic acid was used as a polymer having no lithium ion conductivity instead of the polymer having lithium ion conductivity. As shown in the "type of polymer" column in Table 2, this polyacrylic acid is a polymer that does not have lithium ion conductivity.

<Measurement of internal resistance>
The lithium ion battery obtained in each example and comparative example was charged and discharged once at 25°C. After that, the battery was fully charged and stored in an environment of 60°C.
Using an impedance measuring device (manufactured by Hioki Electric Co., Ltd., chemical impedance analyzer IM3590), the internal resistance value at a frequency of 1000 Hz was measured after 0 days (immediately after full charge), after storage for 7 days, and after storage for 14 days.
In addition, the difference between the internal resistance value after storage for 0 days (immediately after full charge) and after storage for 14 days (internal resistance value on day 14 - internal resistance value after 0 days) was obtained.
The results are shown in Table 3.

From a comparison between Examples 1 to 9 and Comparative Examples 1 to 3, in a lithium ion battery using the coated electrode active material particles for lithium ion batteries of the present invention as coated positive electrode active material particles for lithium ion batteries, in a high temperature environment It was confirmed that even if stored for a long period of time, the increase in internal resistance value could be reduced.
Further, from a comparison between Examples 10 to 18 and Comparative Examples 4 to 6, it was found that the lithium ion battery using the coated electrode active material particles for lithium ion batteries of the present invention as the coated negative electrode active material particles for lithium ion batteries was in a high temperature environment. It was confirmed that the rise in the internal resistance value can be reduced even when stored for a long period of time.

The coated electrode active material particles for lithium ion batteries of the present invention can reduce the increase in the internal resistance value of the lithium ion battery even when used in a high temperature environment. can be used extensively for

Claims (6)

A coated electrode active material particle for a lithium ion battery in which at least part of the surface of the electrode active material particle is coated with a coating layer,
A coated electrode active material particle for a lithium ion battery, wherein the coating layer includes particles made of a polymer having lithium ion conductivity, a coating resin, and a conductive aid. 2. The coated electrode active material particles for a lithium ion battery according to claim 1, wherein the polymer having lithium ion conductivity is one or more selected from the group consisting of polyethylene oxide, polyacrylonitrile and polyethylene glycol. 3. The coated electrode active material particles for a lithium ion battery according to claim 1, wherein the particles made of a polymer having lithium ion conductivity have a volume average particle diameter of 1 to 50 μm. The weight ratio of the polymer particles having lithium ion conductivity is 0.1 to 5% by weight based on the weight of the coated electrode active material particles, according to any one of claims 1 to 3. Coated electrode active material particles for lithium ion batteries. A lithium ion battery electrode comprising an electrode active material layer containing the coated electrode active material particles for a lithium ion battery according to any one of claims 1 to 4 and an electrolytic solution containing an electrolyte and a solvent,
A lithium ion battery electrode, wherein the coating resin contained in the lithium ion battery electrode has a weight ratio of 1 to 10% by weight based on the weight of the lithium ion battery electrode. The lithium according to any one of claims 1 to 4, which has a step of removing the solvent after mixing the electrode active material particles, the particles made of a polymer having lithium ion conductivity, the coating resin, the conductive aid and the organic solvent. A method for producing coated electrode active material particles for an ion battery.