JP2022152671A - Manufacturing method for lithium-ion battery - Google Patents

Abstract

To provide a manufacturing method for a lithium-ion battery capable of efficiently spreading an electrolyte to an electrode active material layer in a short time.SOLUTION: The manufacturing method for a lithium-ion battery includes: a step of forming an electrode active material layer which forms the electrode active material layer 10 including coated electrode active material particles in which at least part of the surface of the electrode active material particles is coated with a coating layer containing a polymer compound; and a step of pouring electrolyte which pours an electrolyte 30 into the electrode active material layer 10. In the electrolyte pouring step, the electrolyte 30 is discharged at a discharge rate of 1200 to 3500 mm2/s to pour the electrolyte.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for manufacturing a lithium ion battery.

Lithium ion batteries have been widely used in recent years as secondary batteries with high energy density and high power density. In particular, for the purpose of improving the conductivity of the electrode, a lithium ion battery comprising an electrode active material layer having coated electrode active material particles coated with a coating layer containing a polymer compound (for example, Patent Document 1), Due to the method of manufacturing the electrodes, it is possible to manufacture electrodes with a large area (200 cm ² or more), and their use as stationary large-sized batteries is also under study.

JP 2017-054703 A

In recent years, with the increasing size of electrodes, the demand for improving work efficiency is becoming stronger. However, as the size of the electrode increases, the equipment required for the process of injecting the electrolyte solution into the electrode becomes larger and the process time becomes longer, resulting in an increase in the manufacturing cost.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a method for manufacturing a lithium-ion battery that can efficiently spread an electrolytic solution over an electrode active material layer in a short period of time.

The present inventors arrived at the present invention as a result of intensive studies in order to solve the above problems.
The present invention comprises an electrode active material layer forming step of forming an electrode active material layer having coated electrode active material particles in which at least a portion of the surface of the electrode active material particles is coated with a coating layer containing a polymer compound; an electrolytic solution injection step of injecting an electrolytic solution into the material layer, and in the electrolytic solution injection step, injection is performed by discharging the electrolytic solution at a discharge speed of 1200 to 3500 mm ² /s. The present invention relates to a method for manufacturing a lithium ion battery.

ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the lithium ion battery which can spread an electrolyte solution efficiently over an electrode active material layer in a short time can be provided.

FIG. 1 is a perspective view schematically showing an example of the electrolyte injection process. FIG. 2 is a plan view schematically showing a state in which an electrolytic solution is injected in Example 1. FIG. FIG. 3 is a plan view schematically showing a state in which an electrolytic solution is injected in Comparative Examples 1 and 3. FIG. 4 is a plan view schematically showing a state in which an electrolytic solution is injected in Comparative Example 2. FIG. FIG. 5 is a plan view schematically showing a wet state of the electrode active material layer after installing the separator in Example 1. FIG. FIG. 6 is a plan view schematically showing a wet state of the electrode active material layer after installing the separator in Comparative Examples 1 and 3. FIG. FIG. 7 is a plan view schematically showing a wet state of the electrode active material layer after installing the separator in Comparative Example 2. FIG.

The present invention will be described in detail below.
The present invention relates to a method for manufacturing a lithium ion battery.
In addition, in this specification, when describing a lithium ion battery, the concept includes a lithium ion secondary battery.

A lithium-ion battery manufactured by the method for manufacturing a lithium-ion battery of the present invention is a laminate unit composed of a set of positive electrode current collector, positive electrode active material layer, separator, negative electrode active material layer, and negative electrode current collector which are stacked in order. and an electrolytic solution. The lithium-ion battery described above is a configuration example of a single battery.
In this specification, both the positive electrode current collector and the negative electrode current collector, or either one of the positive electrode current collector and the negative electrode current collector may be referred to as "current collector".
In addition, in this specification, both the positive electrode active material layer and the negative electrode active material layer, or either one of the positive electrode active material layer and the negative electrode active material layer may be referred to as an “electrode active material layer”.

The positive electrode active material layer and the negative electrode active material layer are respectively coated positive electrode active material particles in which at least part of the surface of the positive electrode active material particles is coated with a coating layer containing a polymer compound, and at least part of the surface of the negative electrode active material particles. has coated negative electrode active material particles coated with a coating layer containing a polymer compound.
In this specification, both the positive electrode active material particles and the negative electrode active material particles, or either one of the positive electrode active material particles and the negative electrode active material particles may be referred to as "electrode active material particles".
In this specification, both coated positive electrode active material particles and coated negative electrode active material particles, or either one of the coated positive electrode active material particles and the coated negative electrode active material particles are referred to as “coated electrode active material particles”. Sometimes.

The method for producing a lithium ion battery of the present invention comprises an electrode active material layer having coated electrode active material particles in which at least a part of the surface of the electrode active material particles is coated with a coating layer containing a polymer compound. and an electrolytic solution injection step of ^injecting an electrolytic solution into the electrode active material layer. It is characterized by performing liquid.
In the method for producing a lithium-ion battery of the present invention, the electrolytic solution is discharged at a discharge speed of 1200 to 3500 mm ² /s to inject the electrolytic solution into the electrode active material layer, thereby efficiently discharging the electrolytic solution into the electrode active material layer in a short time. Therefore, it is possible to efficiently fabricate a large-area electrode. According to the manufacturing method of the present invention, the electrolytic solution may be injected into either the positive electrode active material layer or the negative electrode active material layer, or the electrolytic solution may be injected into both the positive electrode active material layer and the negative electrode active material layer. may

First, the electrode active material layer forming step for forming the electrode active material layer will be described.
In the coated electrode active material particles of the electrode active material layer, at least part of the surface of the electrode active material particles is coated with a coating layer containing a polymer compound.
The coated electrode active material particles may be produced, for example, by a method of mixing a polymer compound and an electrode active material particle. After preparing the coating material by mixing the coating material and the electrode active material particles, the polymer compound, the conductive agent, and the electrode active material particles can be mixed at once. may be manufactured. When the electrode active material particles, the polymer compound, and the conductive agent are mixed, the mixing order is not particularly limited, but after mixing the electrode active material particles and the polymer compound, the conductive agent is added and further mixed. preferably.
At least part of the surface of the electrode active material particles is coated with the coating layer containing the polymer compound by the above method.

Although the method for forming the electrode active material layer is not particularly limited, it can be formed, for example, using an electrode composition containing coated electrode active material particles.
The electrode active material layer can be formed, for example, by applying an electrode composition containing coated electrode active material particles and a small amount of electrolytic solution to the surface of a current collector or substrate and removing excess electrolytic solution, or by a method of removing excess electrolytic solution. and a method of molding an electrode composition containing a small amount of electrolytic solution on a substrate by applying pressure or the like. When the electrode active material layer is formed on the surface of the substrate, the electrode active material layer can be combined with the current collector by a method such as transfer.
If necessary, the electrode composition may further contain a conductive aid, a known solution-drying type binder for electrodes (also referred to as a binder), and an adhesive resin. In addition, the conductive agent used for producing the electrode active material layer is different from the conductive agent contained in the coating layer, exists outside the coating layer of the coated electrode active material particles, and is present in the electrode active material layer. It has the function of improving electron conductivity from the surface of the active material particles. The electrode composition preferably does not contain a solution-drying electrode binder.

Next, the electrolyte injection step of injecting the electrolyte into the electrode active material layer will be described.
In the electrolytic solution injection step, the electrolytic solution is discharged at a discharge speed of 1200 to 3500 mm ² /s to be injected into the electrode active material layer. With this ejection speed, the electrolytic solution can be efficiently injected in a short time even in the case of manufacturing a large-sized lithium ion battery. A preferable ejection speed is 1400 to 3300 mm ² /s.

The means for injecting the electrolytic solution into the electrode active material layer is not particularly limited as long as it can inject the electrolytic solution at the above-mentioned ejection speed, but it is selected from the group consisting of a spray coater, a dispenser, a die coater and a roll coater. It is preferable to use at least one kind of liquid injection means. By using these injection means, it is possible to uniformly and efficiently inject the electrolytic solution into the electrode active material layer.
The spray coater may be an air spray system, an airless spray system, or an electrostatic spray system, and examples thereof include a system in which a syringe including a valve capable of spray coating is combined with a metered discharge device.
Valves that can be applied in a spray form include, for example, SV91, SV70, SV71, and SV97MS (all manufactured by Sanei Tech Co., Ltd.).
As a fixed amount discharge device, a device generally used for conformal coating, for example, a dispenser SDP520 (manufactured by Sanei Tech Co., Ltd.) can be used.

In this specification, the dispenser refers not only to a fixed quantity discharge device, but also to a whole system in which an adapter tube, a syringe, a plunger, a needle and the like are combined with a fixed quantity discharge device.
As dispensers, systems commonly used for conformal coating can be used.
As the fixed amount discharge device, the same device as that usable in the spray coater can be used.
Examples of valves used for dispenser syringes include SV70, SV71, SV91MS, SV91CD, and SV97MS (all manufactured by Sanei Tech Co., Ltd.).
Examples of the form of ejection from the dispenser include dots, lines, and the like.

Examples of the die coater include a die coater manufactured by Matsuoka Kikai Seisakusho Co., Ltd., and the like.
Examples of the roll coater include a 500 mm width roll coater (web coater) (manufactured by Fuji R&D Co., Ltd.).

Any one of a spray coater, a dispenser, a die coater and a roll coater may be used as the injection means, or two or more of them may be used in combination. Further, for example, when a spray coater or a dispenser is used as the injection means, it is possible to divide the injection into multiple times using different valves.

In the electrolytic solution injection step, the temperature of the electrolytic solution injected into the electrode active material layer is not particularly limited, but is preferably 10 to 70°C, more preferably 20 to 60°C. When the temperature of the electrolytic solution is within the above range, the electrolytic solution has a viscosity that facilitates permeation of the electrode active material layer.

In the production method of the present invention, it is possible to inject the electrolytic solution into the electrode active material layer formed on the substrate. It is preferable to inject the electrolytic solution into the contacting electrode active material layer. More preferably, an electrode active material layer is formed on a resin current collector, and an electrolytic solution is injected into the electrode active material layer in contact with the resin current collector.

FIG. 1 is a perspective view schematically showing an example of the electrolyte injection process. In FIG. 1, the electrolytic solution 30 is injected into the electrode active material layer 10 formed on the current collector 20 using the spray coater 40 . The spray coater 40 shown in FIG. 1 is a system using the above-described fixed quantity discharge device, and can inject the electrolytic solution 30 in a state where the spray coater 40 does not contact the electrode active material layer 10 .

In the method for producing a lithium ion battery of the present invention, after injecting the electrolyte into the electrode active material layer in the electrolyte injection step, if necessary, a current collector, a separator, etc. are combined, and then the outer periphery is sealed. By doing so, a lithium ion battery can be obtained.

Next, a preferable configuration of the lithium ion battery manufactured by the lithium ion battery manufacturing method of the present invention will be described.
A resin current collector or a metal current collector can be used as the positive electrode current collector and the negative electrode current collector. A resin current collector is particularly preferred.
The resin current collector preferably contains a conductive filler and a resin (also referred to as a matrix resin) that constitutes the base of the resin current collector.
Examples of matrix resins include polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), polycycloolefin (PCO), polyethylene terephthalate (PET), polyethernitrile (PEN), polytetrafluoroethylene (PTFE ), styrene-butadiene rubber (SBR), polyacrylonitrile (PAN), polymethyl acrylate (PMA), polymethyl methacrylate (PMMA), polyvinylidene fluoride (PVdF), epoxy resins, silicone resins or mixtures thereof.
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 conductive filler is selected from materials having electrical conductivity.
Specifically, metal [nickel, aluminum, stainless steel (SUS), silver, copper, titanium, etc.], carbon [graphite and carbon black (acetylene black, ketjen black, furnace black, channel black, thermal lamp black, etc.), etc. ], and mixtures thereof, but are not limited thereto.
These conductive fillers may be used singly or in combination of two or more. Also, alloys or metal oxides thereof may be used. From the viewpoint of electrical stability, aluminum, stainless steel, carbon, silver, copper, titanium and mixtures thereof are preferred, silver, aluminum, stainless steel and carbon are more preferred, and carbon is even more preferred. These conductive fillers may be those obtained by coating a conductive material (a metal material among the conductive filler materials described above) around a particulate ceramic material or a resin material by plating or the like.
The resin current collector may contain other components (dispersant, cross-linking accelerator, cross-linking agent, colorant, ultraviolet absorber, plasticizer, etc.) in addition to the matrix resin and the conductive filler.

Examples of positive electrode active material particles contained in the positive electrode active material layer 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.), composite oxides containing two transition metal elements (eg, 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 composite oxides containing three or more metal elements [for example, LiM _a M′ _b M″ _c O ₂ (M, M′ and M '' are respectively different transition metal elements and _satisfy a+ _{b + c} = ₁ . _LiCoPO4 , _LiMnPO4 and _LiNiPO4 ), transition metal oxides ₍ e.g. _MnO2 and _V2O5 ), transition metal sulfides ₍ e.g. MoS2 and _TiS2 ) and conductive polymers (e.g. polyaniline, polypyrrole, polythiophene, polyacetylene, poly-p-phenylene and polyvinylcarbazole) and the like, and two or more of them may be used in combination.
The lithium-containing transition metal phosphate may have a transition metal site partially substituted with another transition metal.

Examples of the negative electrode active material particles contained in the negative electrode active material layer include carbon-based materials [graphite, non-graphitizable carbon, amorphous carbon, baked resin bodies (for example, carbonized products obtained by baking phenolic resins and furan resins, etc.), Cokes (e.g. pitch coke, needle coke, petroleum coke, etc.) and carbon fibers, etc.], silicon-based materials [silicon, silicon oxide (SiOx), silicon-carbon composites (surface of carbon particles with silicon and / or silicon carbide silicon particles, 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 oxides, lithium-titanium oxides, etc.), metal alloys (e.g., lithium-tin alloys, lithium-aluminum alloys, lithium-aluminum-manganese alloys, etc.), etc., and mixtures of these with carbonaceous materials, etc. mentioned.
Among the negative electrode active material particles described above, those that do not contain lithium or lithium ions inside may be subjected to a pre-doping treatment in which lithium or lithium ions are contained in part or all of the negative electrode active material particles in advance.

The coating layer that covers at least part of the surface of the electrode active material particles contains a polymer compound.
The polymer compound is preferably, for example, a resin containing a polymer having the acrylic monomer (a) as an essential constituent monomer.
Specifically, the polymer compound constituting the coating layer of the coated positive electrode active material particles is preferably a polymer of a monomer composition containing acrylic acid (a0) as the acrylic monomer (a). In the monomer composition, the content of acrylic acid (a0) is preferably more than 90% by weight and 98% by weight or less based on the total weight of the monomers. From the viewpoint of flexibility of the coating layer, the content of acrylic acid (a0) is more preferably 93.0 to 97.5% by weight, more preferably 95.0 to 97.5% by weight, based on the total weight of the monomers. More preferably 0% by weight.
The polymer compound constituting the coating layer of the coated negative electrode active material particles 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 polymer compound constituting the coating layer 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 polymer compound constituting the coating layer 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.

Monomers (a2) are classified into (a21) and (a22) depending on the group of ^R2 .
(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 polymer compound constituting the coating layer 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 polymer compound constituting the coating layer is a polymer of a monomer composition containing acrylic acid (a0) and at least one of monomer (a1), monomer (a2) and ester compound (a3). Preferably, it is a polymer of a monomer composition containing acrylic acid (a0) and at least one of the monomer (a1), the ester compound (a21) and the ester compound (a3), It is more preferably a polymer of a monomer composition containing acrylic acid (a0) and any one of monomer (a1), monomer (a2) and ester compound (a3), and acrylic acid (a0 ) and any one of the monomer (a1), the ester compound (a21) and the ester compound (a3).
Examples of the polymer compound constituting the coating layer include, for example, a copolymer of acrylic acid and maleic acid using maleic acid as the monomer (a1), and acrylic acid using 2-ethylhexyl methacrylate as the monomer (a2). and a copolymer of 2-ethylhexyl methacrylate, a copolymer of acrylic acid and methyl methacrylate using methyl methacrylate as the ester compound (a3), and the like.

The total content of the monomer (a1), the monomer (a2) and the ester compound (a3) is 2.0% based on the total weight of the monomers, from the viewpoint of suppressing the volume change of the positive electrode active material particles and the negative electrode active material particles. It is preferably 0 to 9.9% by weight, more preferably 2.5 to 7.0% by weight.

The polymer compound constituting the coating layer preferably 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.

Further, the polymer compound constituting the coating layer is copolymerized 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 radically polymerizable monomer (a5), which is possible.
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 polymer compound constituting the coating layer 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 upper limit of the weight average molecular weight of the polymer compound is preferably 100,000, more preferably 70,000.

The weight average molecular weight of the polymer compound constituting the coating layer can be determined by gel permeation chromatography (hereinafter abbreviated as GPC) measurement under the following conditions.
Apparatus: Alliance GPC V2000 (manufactured by Waters)
Solvent: orthodichlorobenzene, N,N-dimethylformamide (hereinafter abbreviated as DMF), tetrahydrofuran Standard material: 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 polymer compound constituting the coating layer 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.). It can be produced by a polymerization method (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 DMF) and ketones (having 3 to 9 carbon atoms, such as methyl ethyl ketone). The amount used is preferably 5 to 900% by weight, more preferably 10 to 400% by weight, still more preferably 30 to 300% by weight based on the total weight of the monomers, and the monomer concentration is preferably 10 to 95% by weight. , more preferably 20 to 90% by weight, 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 polymer compound constituting the coating layer is a cross-linking agent (A') {preferably a polyepoxy compound (a'1) [polyglycidyl ether (bisphenol A diglycidyl ether, propylene glycol diglycidyl ether and glycerol triglycidyl ether) and polyglycidylamines (N,N-diglycidylaniline and 1,3-bis(N,N-diglycidylaminomethyl)) and/or It may be a crosslinked polymer obtained by crosslinking with a polyol compound (a'2) (ethylene glycol, etc.).

Examples of the method of cross-linking the polymer compound forming the coating layer using the cross-linking agent (A′) include a method in which the electrode active material particles are coated with the polymer compound forming the coating layer and then cross-linked. Specifically, the electrode active material particles and a resin solution containing a polymer compound constituting the coating layer are mixed and the solvent is removed to produce coated electrode active material particles, and then a solution containing a cross-linking agent (A′) is mixed with the coated electrode active material particles and heated to cause removal of the solvent and a cross-linking reaction, and the reaction in which the polymer compound constituting the coating layer is cross-linked by the cross-linking agent (A') is the electrode active material A method of raising on the surface of particles can be mentioned.
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.

The coating layer may further contain a conductive agent and ceramic particles in addition to the polymer compound.
As the conductive agent, the same materials as those exemplified as the conductive filler contained in the resin current collector can be used.

Ceramic particles include metal carbide particles, metal oxide particles, glass ceramic particles, and the like.

Examples of metal carbide particles include silicon carbide (SiC), tungsten carbide (WC), molybdenum carbide (Mo ₂ C), titanium carbide (TiC), tantalum carbide (TaC), niobium carbide (NbC), vanadium carbide (VC ), zirconium carbide (ZrC), and the like.

Examples of metal oxide particles include zinc oxide (ZnO), aluminum oxide (Al ₂ O ₃ ), silicon dioxide (SiO ₂ ), tin oxide (SnO ₂ ), titania (TiO ₂ ), zirconia (ZrO ₂ ), _{Indium oxide ( In2O3} ), _Li2B4O7 , _Li4Ti5O12 , _Li2Ti2O5 , _{LiTaO3 , LiNbO3 , LiAlO2 , Li2ZrO3 , Li2WO4 , Li 2} TiO ₃ , Li ₃ PO ₄ , Li ₂ MoO ₄ , Li ₃ BO ₃ , LiBO ₂ , Li ₂ CO ₃ , Li ₂ SiO ₃ and ABO ₃ (where A is Ca, Sr, Ba, La, Pr and Y, and B is at least one selected from the group consisting of Ni, Ti, V, Cr, Mn, Fe, Co, Mo, Ru, Rh, Pd and Re. species), and the like.
As the metal oxide particles, zinc oxide (ZnO), aluminum oxide (Al ₂ O ₃ ), silicon dioxide (SiO ₂ ), and lithium tetraborate (Li ₂ B ₄ O ₇ ).

The ceramic particles are preferably glass-ceramic particles from the viewpoint of suitably suppressing side reactions occurring between the electrolytic solution and the coated positive electrode active material particles.
These may be used individually by 1 type, and may use 2 or more types together.

The glass-ceramic particles are preferably a lithium-containing phosphate compound having a rhombohedral system, and the chemical formula thereof is Li _x M″ ₂ P ₃ O ₁₂ (X=1 to 1.7).
Here, M″ is one or more elements selected from the group consisting of Zr, Ti, Fe, Mn, Co, Cr, Ca, Mg, Sr, Y, Sc, Sn, La, Ge, Nb and Al. Also, part of P may be replaced with _Si or B, and part of O may be replaced with F, Cl, etc. _For example _{, Li1.15Ti1.85Al0.15Si0.05P2 . 95} O ₁₂ , Li _1.2 Ti _1.8 Al _0.1 Ge _0.1 Si _0.05 P _2.95 O ₁₂ and the like can be used.
Also, materials with different compositions may be mixed or combined, and the surface may be coated with a glass electrolyte or the like. Alternatively, it is preferable to use glass-ceramic particles that precipitate a crystal phase of a lithium-containing phosphate compound having a NASICON-type structure by heat treatment.
Glass electrolytes include the glass electrolytes described in JP-A-2019-96478.

Here, the mixing ratio of Li ₂ O in the glass-ceramic particles is preferably 8 mass % or less in terms of oxide.
Even if it is not a NASICON type structure, it consists of Li, La, Mg, Ca, Fe, Co, Cr, Mn, Ti, Zr, Sn, Y, Sc, P, Si, O, In, Nb, F, LISICON type, A solid electrolyte that has perovskite-type, β-Fe ₂ (SO ₄ ) ₃ -type, and Li ₃ In ₂ (PO ₄ ) ₃ -type crystal structures and conducts Li ions at room temperature at a rate of 1×10 ⁻⁵ S/cm or more. may be used.

The ceramic particles described above may be used singly or in combination of two or more.

The volume average particle diameter of the ceramic particles is preferably 1 to 1000 nm, more preferably 1 to 500 nm, even more preferably 1 to 150 nm, from the viewpoints of energy density and electrical resistance.
In the present specification, the volume average particle size means the particle size (Dv50) at 50% integrated value in the particle size distribution determined by the microtrack method (laser diffraction/scattering method). The microtrack method is a method of obtaining a particle size distribution by utilizing scattered light obtained by irradiating particles with laser light. For the measurement of the volume average particle size, a Microtrac manufactured by Nikkiso Co., Ltd. or the like can be used.

The weight ratio of the ceramic particles is preferably 0.5 to 5.0% by weight based on the weight of the coated positive electrode active material particles.
By containing the ceramic particles in the above range, side reactions that occur between the electrolytic solution and the coated positive electrode active material particles can be suitably suppressed.
More preferably, the weight ratio of the ceramic particles is 2.0 to 4.0% by weight based on the weight of the coated positive electrode active material particles.

If necessary, the electrode active material layer may further contain a conductive aid, a solution-drying type known electrode binder (also referred to as a binder), and an adhesive resin.
Examples of the conductive aid include those mentioned above as specific examples of the conductive filler contained in the resin current collector.

Solution-drying binders for electrodes (such as PVDF-based binders, SBR-based binders, and CMC-based binders) are used by dissolving or dispersing a polymer compound in a solvent. It solidifies and firmly adheres and fixes the active materials together and the active material and the current collector, and the electrode binder from which the solvent component has been volatilized does not have stickiness.
Therefore, the solution-drying electrode binder and the adhesive resin are different materials.
Moreover, it is preferable that the electrode active material layer does not contain a solution-drying electrode binder.
It can be said that the electrode active material layer that does not contain a solution-drying type electrode binder is composed of a non-bound body of the coated electrode active material.

As the adhesive resin, for example, a non-aqueous secondary battery active material coating resin described in JP-A-2017-054703 is mixed with a small amount of an organic solvent to adjust its glass transition temperature to room temperature or lower. Also, those described as adhesives in JP-A-10-255805 can be preferably used.
The tacky resin means a resin that has tackiness (property of adhering by applying a slight pressure without using water, solvent, heat, etc.) in a state that does not contain a solvent component.

Separators include microporous films made of polyethylene or polypropylene, multilayer films of porous polyethylene film and polypropylene, non-woven fabrics made of polyester fiber, aramid fiber, glass fiber, etc., and silica, alumina, titania, etc. on their surfaces. known lithium-ion battery separators, such as those to which ceramic fine particles are attached.

As the electrolytic solution, a known electrolytic solution containing an electrolyte and a solvent, which is used for manufacturing known lithium ion batteries, can be used.

_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.
Since such an electrolytic solution has an appropriate viscosity, a liquid film can be formed between the coated electrode active material particles, and the coated electrode active material particles have a lubricating effect (position adjustment ability of the coated electrode active material particles). can be granted.

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.

<Preparation of polymer compound for coating>
150 parts of DMF was charged into a four-necked flask 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 composition containing 91 parts of acrylic acid, 9 parts of methyl methacrylate and 50 parts of DMF, 0.3 parts of 2,2′-azobis(2,4-dimethylvaleronitrile) and 2,2′- An initiator solution prepared by dissolving 0.8 parts of azobis(2-methylbutyronitrile) in 30 parts of DMF was continuously added dropwise over 2 hours with a dropping funnel under stirring while blowing nitrogen into a four-necked flask. radical polymerization was carried out. After the dropwise addition was completed, the reaction was continued at 75° C. for 3 hours. Then, the temperature was raised to 80° C. and the reaction was continued for 3 hours to obtain a copolymer solution with a resin concentration of 30%. The resulting copolymer solution was transferred to a Teflon (registered trademark) vat and dried under reduced pressure at 150° C. and 0.01 MPa for 3 hours, and DMF was distilled off to obtain a copolymer. After roughly pulverizing this copolymer with a hammer, it was additionally pulverized with a mortar to obtain a powdery polymer compound for coating.

<Preparation of electrolytic solution>
LiFSI (LiN(FSO ₂ ) ₂ ) was dissolved at a ratio of 2.0 mol/L in a mixed solvent of ethylene carbonate (EC) and propylene carbonate (PC) (volume ratio of EC:PC: 3:7) to prepare an electrolytic solution. made.

[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 dispersing agent [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 400 mm×500 mm, nickel deposition was performed on one side, and a resin current collector was obtained.

[Production of coated negative electrode active material particles]
One part of the coating polymer compound was dissolved in 3 parts of DMF to obtain a solution of the coating polymer compound.
76 parts of negative electrode active material particles (hard carbon powder, volume average particle size 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. 9 parts of the solution was added dropwise over 2 minutes and stirred for an additional 5 minutes.
Next, while stirring, 9 parts of acetylene black [Denka Black (registered trademark) manufactured by Denka Co., Ltd.], which is a conductive agent, 2 parts of carbon nanofiber [manufactured by Teijin Limited] and glass ceramic particles (trade name “lithium ion Conductive glass-ceramics LICGC ^TM PW-01 (1 μm)” [manufactured by Ohara Co., Ltd.], volume average particle size 1000 nm) was added in 2 minutes while being divided, 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 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 obtain coated negative electrode active material particles.

[Preparation of negative electrode for lithium ion battery]
42 parts of the electrolytic solution and 4.2 parts of carbon fiber [Donacarb Milled S-243 manufactured by Osaka Gas Chemicals Co., Ltd.: average fiber length 500 μm, average fiber diameter 13 μm: electrical conductivity 200 mS / cm] and planetary stirring type mixing and kneading. Mixed for 5 minutes at 2000 rpm using a device {Thubber Mixer [manufactured by Thinky Co., Ltd.]}, then 30 parts of the electrolytic solution and 206 parts of the coated negative electrode active material particles were added, and then further mixed. Mix with Taro at 2000 rpm for 2 minutes, add 20 parts of the above electrolytic solution, stir with a mixing mixer at 2000 rpm for 1 minute, add 2.3 parts of the electrolytic solution, and then mix with a mixing mixer. Stirring was performed at 2000 rpm for 2 minutes to prepare a negative electrode active material layer slurry. The obtained negative electrode active material layer slurry was applied to one side of the resin current collector so that the basis weight was 80 mg/cm ² and pressed at a pressure of 1.4 MPa for about 10 seconds to obtain a thickness of 340 μm. A negative electrode for a lithium ion battery (370 mm×470 mm) according to Example 1 was produced.

<Example 1>
The negative electrode active material layer of the lithium ion battery negative electrode prepared above was placed on the upper surface. As an injection device, a dispenser SDP520 (manufactured by San-ei Tech Co., Ltd.) was combined with a spray valve SV91 (manufactured by San-ei Tech Co., Ltd.), and 35 mL of the electrolytic solution prepared above was discharged at 40 ° C. and a discharge rate of 2500 mm ² /s. was applied to the negative electrode active material layer in the form of a spray as shown in FIG. The electrolytic solution was supplied to the injection device using a Heishin mono pump (manufactured by Hyoshinso Co., Ltd., general-purpose series NE type) at a pump pressure of 0.2 MPa. The working time for injection was 1 minute.

The evaluation was performed based on the surface wettability (%) of the electrode active material layer and working time (minutes). Since it is difficult to see the wetting of the electrode active material layer visually, and the surface wettability increases due to the placement of the separator, the surface wettability is evaluated after placing a separator (#3501 manufactured by Celgard) on the electrode active material layer. I went by sight. Table 1 shows the results.
As shown in FIG. 5, when the separator is installed after the electrolytic solution is injected, the wetted area of the electrode active material layer becomes larger than that during the injection.

<Example 2>
The electrolytic solution was applied to the negative electrode active material layer under the same conditions as in Example 1, except that a die coater (manufactured by Matsuoka Kikai Seisakusho Co., Ltd.) was used as the injection device, and the ejection speed was changed to 3200 mm ² /s. and evaluated. Table 1 shows the results.

<Example 3>
A conformal valve SV70 (Sanei Tech Co., Ltd.) was used instead of the spray valve SV91, and the electrolytic solution was applied to the negative electrode active material under the same conditions as in Example 1 except that the droplets were applied in dots at an ejection speed of 2300 mm ² /s. A layer was applied and evaluated. Table 1 shows the results.

<Example 4>
Electrolysis was performed under the same conditions as in Example 1, except that a roll coater [manufactured by Fuji R&D Co., Ltd., 500 mm width roll coater (web coater)] was used as the injection device, and the ejection speed was changed to 1500 mm ² /s. The liquid was applied to the negative electrode active material layer and evaluated. Table 1 shows the results.

<Example 5>
The electrolytic solution was applied to the negative electrode active material layer under the same conditions as in Example 1, except that the temperature of the electrolytic solution was changed to 20° C., the ejection speed was changed to 2000 mm ² /s, and the pump pressure was changed to 0.4 MPa, and evaluation was performed. rice field. Table 1 shows the results.

<Example 6>
The electrolytic solution was applied to the negative electrode active material layer under the same conditions as in Example 3, except that the temperature of the electrolytic solution was changed to 20° C., the ejection speed was changed to 1800 mm ² /s, and the pump pressure was changed to 0.3 MPa. rice field. Table 1 shows the results.

<Example 7>
The electrolytic solution was applied to the negative electrode active material layer under the same conditions as in Example 1, except that the temperature of the electrolytic solution was changed to 60° C., the ejection speed was changed to 3000 mm ² /s, and the pump pressure was changed to 0.1 MPa, and evaluation was performed. rice field. Table 1 shows the results.

<Comparative Example 1>
The negative electrode active material layer of the lithium ion battery negative electrode prepared above was placed on the upper surface. 35 mL of the electrolytic solution prepared above was manually applied to the negative electrode active material layer in dots as shown in FIG. The temperature of the electrolytic solution was 40° C., the discharge speed was 500 mm ² /s, and the working time for the injection was 5 minutes. Table 1 shows the results. FIG. 6 schematically shows a wet state of the electrode active material layer after installing the separator.

<Comparative Example 2>
Manually under the same conditions as in Comparative Example 1 except that an 8-channel pipette (Pipette PAL Plus 8ch PALP-8-10, manufactured by Tokyo Glass Instruments) was used instead of the dropper, the negative electrode active material layer was manually formed as shown in FIG. The electrolytic solution was applied in a dot pattern on the surface and evaluated. The ejection speed was 50 mm ² /s, and the work time for liquid injection was 50 minutes. Table 1 shows the results. FIG. 7 schematically shows a wet state of the electrode active material layer after the separator is installed.

<Comparative Example 3>
The electrolytic solution was applied to the negative electrode active material layer under the same conditions as in Comparative Example 1, except that the temperature of the electrolytic solution was changed to 20° C., and evaluation was performed. Table 1 shows the results. FIG. 6 schematically shows a wet state of the electrode active material layer after the separator is installed.

As shown in Table 1, an example in which a spray coater, a dispenser, a die coater, or a roll coater was used as the injection device, and the electrolytic solution was discharged at a discharge speed of 1200 to 3500 mm ² /s to perform injection. In 1 to 7, compared to Comparative Examples 1 to 3, in which the liquid was manually injected using a dropper or an 8-channel pipette, the electrolytic solution was injected into the electrode active material layer with a wider area in a short working time. and the surface wettability after installing the separator was high.

The method for producing a lithium ion battery of the present invention is particularly useful as a method for efficiently injecting an electrolytic solution into electrodes of a large lithium ion battery.

10 electrode active material layer 20 current collector 30 electrolytic solution 40 spray coater (liquid injection means)
50 Separator

Claims (3)

an electrode active material layer forming step of forming an electrode active material layer having coated electrode active material particles in which at least a portion of the surface of the electrode active material particles is coated with a coating layer containing a polymer compound;
an electrolytic solution injection step of injecting an electrolytic solution into the electrode active material layer;
A method for manufacturing a lithium ion battery, wherein in the electrolyte injection step, the electrolyte is discharged at a discharge speed of 1200 to 3500 mm ² /s. 2. The manufacture of a lithium ion battery according to claim 1, wherein in the electrolyte pouring step, the electrolyte is poured by at least one pouring means selected from the group consisting of a spray coater, a dispenser, a die coater and a roll coater. Method. The electrode active material layer is formed on a resin current collector,
3. The method of manufacturing a lithium ion battery according to claim 1, wherein in said electrolyte injection step, an electrolyte is injected into said electrode active material layer in contact with said resin current collector.

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