WO2018117086A1

WO2018117086A1 - Negative electrode for lithium ion batteries and method for producing negative electrode for lithium ion batteries

Info

Publication number: WO2018117086A1
Application number: PCT/JP2017/045484
Authority: WO
Inventors: 和也土田; 勇輔中嶋; 大澤　康彦; 雄樹草地; 佐藤　一; 赤間　弘; 堀江　英明
Original assignee: 日産自動車株式会社
Priority date: 2016-12-20
Filing date: 2017-12-19
Publication date: 2018-06-28
Also published as: MY174406A

Abstract

[Problem] To provide: a negative electrode for lithium ion batteries, wherein volume change of a silicon-based negative electrode active material due to charge and discharge is suppressed; and a method for producing this negative electrode for lithium ion batteries. [Solution] A method for producing a negative electrode for lithium ion batteries, which comprises a step for forming a coating film on a collector or a separator with use of a slurry that contains a dispersion medium and a negative electrode active material composition containing a silicon-based negative electrode active material and a carbon-based negative electrode active material. This method for producing a negative electrode for lithium ion batteries comprises, before or after the step for forming a coating film and before the assembly of a lithium ion battery, a step for doping the silicon-based negative electrode active material with lithium ions and a step for doping the carbon-based negative electrode active material with lithium ions, without substantially comprising a step for drying the coating film.

Description

Negative electrode for lithium ion battery and method for producing negative electrode for lithium ion battery

The present invention relates to a negative electrode for a lithium ion battery and a method for producing a negative electrode for a lithium ion battery.

In recent years, reduction of carbon dioxide emissions has been strongly desired for environmental protection. In the automobile industry, there are high expectations for reducing carbon dioxide emissions by introducing electric vehicles (EVs) and hybrid electric vehicles (HEVs), and we are eager to develop secondary batteries for motor drives that hold the key to their practical application. Has been done. As a secondary battery, attention is focused on a lithium ion battery that can achieve a high energy density and a high output density.

In order to increase the energy density of lithium ion batteries, silicon-based materials (such as silicon and silicon compounds) having a larger theoretical capacity than carbon materials conventionally used as negative electrode active materials have attracted attention. However, when a silicon-based material is used as the negative electrode active material, the volume change of the material accompanying charge / discharge is large. For this reason, the silicon-based material is self-destructed by volume change or is easily peeled off from the current collector surface, so that it is difficult to improve cycle characteristics.

In Patent Document 1, the mixing ratio of at least one of silicon (hereinafter also referred to as silicon) and silicon compound (hereinafter also referred to as silicon compound) and carbon, and the particle diameter thereof are adjusted to a predetermined range. Discloses a lithium ion battery in which expansion of the negative electrode is suppressed.

Patent Document 2 includes carbon particles and fibrous carbon in which a carbonaceous material containing Si and / or Si compound is attached to at least a part of the surface of carbon particles having a graphite structure, and the carbonaceous material contains a polymer. A carbon material obtained by heat-treating a composition is disclosed. Furthermore, an electrode paste including the carbon material and a binder (binder) and an electrode including the electrode paste are also disclosed.

Japanese Unexamined Patent Application Publication No. 2016-103337 (U.S. Patent Application Publication No. 2016/156025) JP 2004-182512 A

However, since the electrode (negative electrode) described in Patent Documents 1 and 2 uses a binder, if the electrode thickness is excessively increased, the negative electrode active material is peeled off from the surface of the negative electrode current collector. There was a problem. Moreover, since the proportion of the active material is reduced by the amount of the binder used, there is a problem that the energy density is lowered. In addition, the binder may limit the expansion and contraction of silicon and silicon compound, and may easily break. Furthermore, the effect of suppressing the expansion of the negative electrode during charging is not sufficient, and there is room for further improvement. Hereinafter, silicon and silicon compounds used as the negative electrode active material are collectively referred to as “silicon-based negative electrode active material” in this specification.

In addition, the volume change of the silicon-based negative electrode active material becomes most remarkable at the first charge / discharge when the silicon-based negative electrode active material occludes / releases lithium ions. Therefore, it is considered important to suppress the volume change at the first charge / discharge for improving the characteristics of the negative electrode.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a negative electrode for a lithium ion battery in which the volume change of the silicon-based negative electrode active material due to charge / discharge is small and a method for producing the same.

The inventors of the present invention have arrived at the present invention as a result of intensive studies to solve the above problems.

That is, this invention has the process of forming a coating film on a collector or a separator using the slurry containing the negative electrode active material composition containing a silicon type negative electrode active material and a carbon type negative electrode active material, and a dispersion medium. The present invention relates to a method for producing a negative electrode for a lithium ion battery. The manufacturing method includes a step of doping a lithium-based negative electrode active material with lithium ions before or after a step of forming a coating film and before assembling a lithium-ion battery, and a step of doping lithium ions into a carbon-based negative electrode active material. Including the step of. And it has the characteristics in the point which does not contain the process of drying a coating film substantially.

According to the method for producing a negative electrode for a lithium ion battery of the present invention, it is possible to provide a negative electrode for a lithium ion battery in which the volume change of the silicon-based negative electrode active material due to charge / discharge is small.

Hereinafter, the present invention will be described in detail.

First, the negative electrode for a lithium ion battery obtained by the production method of the present invention will be described. The negative electrode for a lithium ion battery of the present invention is obtained by a production method described later, and includes a carbon-based negative electrode active material doped with lithium ions and a silicon-based negative electrode active material doped with lithium ions. And a negative electrode active material layer made of a non-binding body.

The negative electrode for a lithium ion battery of the present invention includes a negative electrode active material layer. The negative electrode active material layer is composed of a non-binding body of a negative electrode active material composition including a carbon-based negative electrode active material doped with lithium ions and a silicon-based negative electrode active material doped with lithium ions. The negative electrode active material layer is preferably disposed on the negative electrode current collector.

The silicon-based negative electrode active material is preferably silicon and / or a silicon compound. The silicon may be crystalline silicon, amorphous silicon, or a mixture thereof. Examples of the silicon compound include silicon oxide (SiO _x ), Si—C composite, Si—Al alloy, Si—Li alloy, Si—Ni alloy, Si—Fe alloy, Si—Ti alloy, Si—Mn alloy, It is preferably at least one selected from the group consisting of Si—Cu alloys and Si—Sn alloys. Examples of the Si—C composite include silicon carbide, carbon particles whose surfaces are covered with silicon and / or silicon carbide, and silicon particles or silicon oxide particles whose surfaces are covered with carbon and / or silicon carbide. included.

The silicon particles and / or silicon compound particles are preferably aggregated to form composite particles (that is, secondary particles obtained by aggregating primary particles). The composite particles may be those in which only silicon particles and / or silicon oxide particles are aggregated, or may be those in which silicon particles and / or silicon oxide particles are aggregated via a polymer compound. As the polymer compound in this case, for example, the same polymer compound used as a coating resin for a carbon-based coated negative electrode active material described later can be used. Further, the composite particles may contain a conductive aid as necessary. As the conductive assistant at this time, the same conductive assistant as that contained in the negative electrode coating layer of the carbon-based coated negative electrode active material described later can be used. Examples of the method for forming the composite particles include a method of mixing primary particles of silicon and / or silicon compound particles and a coating resin described later.

The volume average particle size of the silicon-based negative electrode active material is not particularly limited, but the primary particle size is preferably 0.01 to 10 μm from the viewpoint of durability, and when the composite particles are formed, the secondary particles More preferably, the diameter is 10 to 30 μm. In addition, although a silicon-type negative electrode active material expand | swells when lithium ion is doped, the volume average particle diameter here means the particle diameter of the silicon-type negative electrode active material before being doped with lithium ion. The volume average particle diameter means a particle diameter (Dv50) at an integrated value of 50% in a particle size distribution obtained by a microtrack method (laser diffraction / scattering method). The microtrack method is a method for obtaining a particle size distribution using scattered light obtained by irradiating particles with laser light, and a microtrack manufactured by Nikkiso Co., Ltd. can be used for the measurement.

The silicon-based negative electrode active material is doped with lithium ions. By being doped with lithium ions, the first charge of the silicon-based negative electrode active material has already been completed. Therefore, the negative electrode for a lithium ion battery is not affected by the first charge / discharge at which the largest volume change occurs and the volume change of the silicon-based negative electrode active material due to the subsequent charge / discharge is small.

Examples of the carbon-based negative electrode active material include carbon-based materials [for example, graphite, non-graphitizable carbon, amorphous carbon, resin fired bodies (for example, those obtained by firing and carbonizing phenol resin, furan resin, etc.), cokes (for example, pitch) Coke, needle coke, petroleum coke, etc.)], or conductive polymers (such as polyacetylene and polypyrrole), metal oxides (titanium oxide and lithium / titanium oxide), and metal alloys (lithium-tin alloys, lithium- A mixture of an aluminum alloy, an aluminum-manganese alloy, etc.) with a carbon-based material.

The volume average particle diameter of the carbon-based negative electrode active material is preferably from 0.1 to 50 μm, and more preferably from 15 to 20 μm, from the viewpoint of the electrical characteristics of the negative electrode for a lithium ion battery. In addition, although a carbon-type negative electrode active material expand | swells by being doped with lithium ion, the volume average particle diameter here is a volume average particle diameter before being doped with lithium ions. The volume average particle diameter means the particle diameter (Dv50) at an integrated value of 50% in the particle size distribution obtained by the microtrack method (laser diffraction / scattering method). The microtrack method is a method for obtaining a particle size distribution using scattered light obtained by irradiating particles with laser light, and a microtrack manufactured by Nikkiso Co., Ltd. can be used for the measurement.

The carbon-based negative electrode active material is also doped with lithium ions.

The negative electrode active material layer is composed of a non-binding body of a negative electrode active material composition including a carbon-based negative electrode active material doped with lithium ions and a silicon-based negative electrode active material doped with lithium ions.

In general, when the first charge / discharge is performed in a lithium ion battery, there are lithium ions that are not released from the negative electrode during discharge, but when the lithium ions are doped in the silicon-based negative electrode active material and the carbon-based negative electrode active material The proportion of the positive electrode active material that bears lithium ions that are not released from the negative electrode is small. Therefore, since the amount of electricity spent for the first charge can be spent for discharging, the irreversible capacity can be reduced.

In addition, since the positive electrode active material that supplies lithium ions during charging is generally expensive, the amount of the positive electrode active material used can be reduced by doping lithium ions in advance. Furthermore, since lithium ions are pre-doped to prevent the electrolyte from decomposing and generating gas during the first charge, there is a possibility that the degassing step can be omitted during the manufacture of the lithium ion battery.

The non-binding body of the negative electrode active material composition means that the silicon-based negative electrode active material and the carbon-based negative electrode active material are not fixed to each other by a binder (also referred to as a binder). The negative electrode active material layer in a conventional lithium ion battery is coated on the surface of a negative electrode current collector or the like with a slurry in which a silicon negative electrode active material, a carbon negative electrode active material, and a binder are dispersed in a dispersion medium (solvent). However, since it is manufactured by heating and drying, the negative electrode active material layer is in a state of being hardened by a binder. At this time, the negative electrode active materials are fixed to each other by the binder, and the positions of the silicon-based negative electrode active material and the carbon-based negative electrode active material are fixed. When the negative electrode active material layer is hardened with a binder, excessive stress is applied to the silicon-based negative electrode active material due to expansion / contraction during charge / discharge, and the self-destructing is likely to occur. Further, since the negative electrode active material layer is fixed on the negative electrode current collector or separator by the binder, the negative electrode active material layer solidified by the binder due to expansion / contraction during charge / discharge of the silicon-based negative electrode active material Cracks may occur, and the negative electrode active material layer may be peeled off from the surface of the negative electrode current collector.

In order to obtain a negative electrode active material layer composed of a non-binding body of the negative electrode active material composition, a coating film made of slurry is dried when forming the negative electrode active material layer in a method for producing a negative electrode for a lithium ion battery described later. The method of making it not include substantially the process to make is mentioned. Further, a negative electrode active material composed of a non-binding material of a negative electrode active material composition can be obtained by a method in which the negative electrode active material layer (slurry for forming the negative electrode active material layer) does not substantially contain a binder. A material layer can be formed. Here, the negative electrode active material layer (slurry for forming the negative electrode active material layer) does not substantially contain a binder. Specifically, the content of the binder is determined by the negative electrode active material layer ( This means that it is 1% by mass or less with respect to 100% by mass of the total solid content contained in the slurry for forming the negative electrode active material layer. The content of the binder is more preferably 0.5% by mass or less, further preferably 0.2% by mass or less, particularly preferably 0.1% by mass or less, and most preferably 0% by mass. %.

In this specification, the binder that the negative electrode active material layer does not substantially contain is a known solvent used for binding and fixing the negative electrode active material particles to each other and the negative electrode active material particles and the current collector. (Dispersion medium) A dry binder for lithium ion batteries, and includes starch, polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose, polyvinylpyrrolidone, tetrafluoroethylene, and styrene-butadiene rubber. These binders for lithium ion batteries are used by being dissolved or dispersed in water or an organic solvent, and are dried and solidified by volatilizing a solvent (dispersion medium) component to form negative electrode active material particles and negative electrode active material particles. And the current collector are firmly fixed. Here, the negative electrode active material particles are a concept including all silicon-based active material particles and carbon-based negative electrode active material particles.

The method for producing a negative electrode for a lithium ion battery does not substantially include a step of drying the slurry of the binder, or the negative electrode active material layer (slurry for forming the negative electrode active material layer) substantially contains the binder. Otherwise, the negative electrode active material particles are not firmly fixed by the binder, and expansion / contraction during charging / discharging of the silicon negative electrode active material is not restricted. Can be suppressed. Furthermore, since the negative electrode active material layer constituting the negative electrode for a lithium ion battery of the present invention is not fixed to the negative electrode current collector surface by a binder, The negative electrode active material layer is not cracked or peeled off due to the shrinkage. Therefore, deterioration of cycle characteristics can be suppressed.
Therefore, the negative electrode for lithium ion batteries of the present invention is excellent in energy density and cycle characteristics. Since the negative electrode active material layer contains a silicon-based negative electrode active material having a large theoretical capacity, the energy density is excellent.

When the negative electrode active material layer contains a silicon-based negative electrode active material and a carbon-based negative electrode active material, the mass mixing ratio of the silicon-based negative electrode active material and the carbon-based negative electrode active material is preferably 5:95 to 50:50. More preferably, it is 30:70 to 45:55. When the mass mixing ratio is within the above range, the effect of improving the energy density by the silicon-based negative electrode active material is sufficient. Moreover, the volume expansion at the time of charge of a negative electrode active material layer does not become large too much. In addition, when a silicon type negative electrode active material contains silicon and a silicon compound, the mass of a silicon type negative electrode active material is defined as the total amount.

The thickness of the negative electrode active material layer is not particularly limited, but is preferably 100 to 1500 μm, more preferably 200 to 800 μm, and further preferably 300 to 600 μm. By setting the thickness of the negative electrode active material layer in the above range, the electrode can be thicker than the conventional negative electrode, and the amount of the active material contained in the negative electrode is increased. Furthermore, since the energy density is increased by including the silicon-based negative electrode active material in the negative electrode active material layer, a negative electrode having a high energy density and a high capacity can be obtained. In addition, the thickness of the negative electrode active material layer is determined before the negative electrode active material layer is charged or when the negative electrode active material layer is discharged to the value of the electrode potential +0.05 V (vs. Li ^/ Li ⁺ ) or less. Of thickness.

The carbon-based negative electrode active material contained in the negative electrode active material layer may be the carbon-based negative electrode active material itself, and includes a polymer compound in which a part or all of the surface of the carbon-based negative electrode active material is a coating resin. The carbon-based coated negative electrode active material coated with the negative electrode coating layer may be a carbon-based coated negative electrode active material. When the surface of the carbon-based negative electrode active material is covered with a coating layer, it is easy to maintain a constant distance between the negative electrode active materials, and it is easy to maintain a conductive path, which is preferable.

When the carbon-based negative electrode active material is a carbon-based coated negative electrode active material doped with lithium ions, it is preferable that lithium ions are doped into the carbon-based negative electrode active material. In other words, lithium ions are not doped in the negative electrode coating layer covering the periphery of the carbon-based coated negative electrode active material, but lithium ions are doped in the carbon-based negative electrode active material at the center of the carbon-based coated negative electrode active material. It is preferable.

The ratio of the mass of the polymer compound to the mass of the carbon-based coated negative electrode active material is not particularly limited, but is preferably 0.01 to 20% by mass.

The negative electrode coating layer comprises a polymer compound that is a coating resin. Moreover, the conductive support agent mentioned later may be further included as needed.

The carbon-based negative electrode active material is a part of or the entire surface of the carbon-based negative electrode active material covered with a negative electrode coating layer containing a polymer compound. In the negative electrode active material layer, Even if the carbon-based coated negative electrode active materials are in contact with each other, the negative electrode coating layers are not irreversibly adhered on the contact surface, and the adhesion is temporary and can be easily loosened by hand. For this reason, the carbon-based coated negative electrode active materials are not fixed by the negative electrode coating layer. Accordingly, in the negative electrode active material layer containing the carbon-based coated negative electrode active material, the carbon-based negative electrode active materials are not bound to each other (that is, a non-binding body of the negative electrode active material composition).

More specifically, whether or not the negative electrode active material layer is made of a non-binding body of the negative electrode active material composition is determined when the negative electrode active material layer is completely impregnated in the electrolytic solution. It can be confirmed by observing whether or not. When the negative electrode active material layer is composed of a binder of the negative electrode active material composition, the shape can be maintained for one minute or longer, but the negative electrode active material layer is composed of a non-binder of the negative electrode active material composition. In some cases, shape collapse occurs in less than a minute.

Examples of the polymer compound constituting the negative electrode coating layer include thermoplastic resins and thermosetting resins. For example, fluororesins, acrylic resins, urethane resins, polyester resins, polyether resins, polyamide resins, epoxy resins, polyimides Examples thereof include resins, silicone resins, phenol resins, melamine resins, urea resins, aniline resins, ionomer resins, polycarbonates, polysaccharides (such as sodium alginate), and mixtures thereof. Among these, acrylic resins, urethane resins, polyester resins and polyamide resins are preferable, and acrylic resins are more preferable.

Among these, a polymer compound having a liquid absorption rate of 10% or more when immersed in an electrolytic solution and a tensile elongation at break in a saturated liquid absorption state of 10% or more is more preferable.

The liquid absorption rate when immersed in the electrolytic solution is obtained by the following equation by measuring the mass of the polymer compound before the immersion in the electrolytic solution and after the immersion.
Absorption rate (%) = [(mass of polymer compound after immersion in electrolyte−mass of polymer compound before immersion in electrolyte) / mass of polymer compound before immersion in electrolyte] × 100
As an electrolytic solution for obtaining the liquid absorption rate, LiPF ₆ is preferably added at 1 mol / liter as an electrolyte in a mixed solvent in which ethylene carbonate (EC) and propylene carbonate (PC) are mixed at a volume ratio of EC: PC = 1: 1. An electrolytic solution dissolved to a concentration of L is used. The immersion in the electrolytic solution for determining the liquid absorption rate is performed at 50 ° C. for 3 days. By immersing at 50 ° C. for 3 days, the polymer compound becomes saturated. The saturated liquid absorption state refers to a state in which the mass of the polymer compound does not increase even when immersed in the electrolyte. In addition, the electrolyte solution used when manufacturing a lithium ion battery using the negative electrode for lithium ion batteries of this invention is not limited to the said electrolyte solution, You may use another electrolyte solution.

When the liquid absorption is 10% or more, lithium ions can easily permeate the polymer compound, so that the ionic resistance in the negative electrode active material layer can be kept low. When the liquid absorption is less than 10%, the lithium ion conductivity is lowered, and the performance as a lithium ion battery may not be sufficiently exhibited. The liquid absorption is preferably 20% or more, and more preferably 30% or more. Moreover, as a preferable upper limit of a liquid absorption rate, it is 400%, and as a more preferable upper limit, it is 300%.

The tensile elongation at break in the saturated liquid absorption state was determined by punching the polymer compound into a dumbbell shape and immersing it in an electrolytic solution at 50 ° C. for 3 days in the same manner as the measurement of the liquid absorption rate. The state can be measured according to ASTM D683 (test piece shape Type II). The tensile elongation at break is a value obtained by calculating the elongation until the test piece breaks in the tensile test according to the following formula.
Tensile elongation at break (%) = [(length of specimen at break−length of specimen before test) / length of specimen before test] × 100
When the tensile elongation at break in the saturated liquid absorption state of the polymer compound is 10% or more, the polymer compound has appropriate flexibility, and therefore the negative electrode coating layer is formed by the volume change of the carbon-based negative electrode active material during charge / discharge. It becomes easy to suppress peeling. The tensile elongation at break is preferably 20% or more, and more preferably 30% or more. Further, the preferable upper limit value of the tensile elongation at break is 400%, and the more preferable upper limit value is 300%.

The acrylic resin is preferably a resin comprising a polymer (A1) having an acrylic monomer (a) as an essential constituent monomer.

The polymer (A1) is a monomer composition comprising a monomer (a1) having a carboxyl group or an acid anhydride group as the acrylic monomer (a) and a monomer (a2) represented by the following general formula (1). A polymer is preferred.
CH ₂ = C (R ¹ ) COOR ² (1)
[In the formula (1), R ¹ represents a hydrogen atom or a methyl group, and R ² represents a straight chain having 4 to 12 carbon atoms or a branched alkyl group having 3 to 36 carbon atoms. ]
Monomers (a1) having a carboxyl group or an acid anhydride group include (meth) acrylic acid (a11), monocarboxylic acids having 3 to 15 carbon atoms such as crotonic acid and cinnamic acid; (anhydrous) maleic acid and fumaric acid Dicarboxylic acids having 4 to 24 carbon atoms such as itaconic acid, citraconic acid and mesaconic acid; polycarboxylic acids having a valence of 6 to 24 carbon atoms such as aconitic acid and the like. Can be mentioned. Among these, (meth) acrylic acid (a11) is preferable, and methacrylic acid is more preferable.

In the monomer (a2) represented by the general formula (1), 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) An ester compound in which R ² is a linear or branched alkyl group having 4 to 12 carbon atoms. Examples of the linear alkyl group having 4 to 12 carbon atoms include a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, Nonyl group, decyl group, undecyl group, dodecyl group can be mentioned.

Examples of the branched alkyl group 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, -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 Tyl 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-methyloctyl group, Tildecyl 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-dimethyl Sil 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. Of these, 2-ethylhexyl group is particularly preferable.

(A22) An 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 a 1-alkylalkyl group [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 groups, 33-alkylalkyl groups, 34-alkylalkyl groups, etc.), and propylene oligomers (7 To 11-mer), ethylene / propylene (molar ratio 16/1 to 1/11) oligomer, isobutylene oligomer (7 to 8-mer), and α-olefin (5 to 20 carbon atoms) oligomer (4 to 8-mer) And a mixed alkyl group containing one or more branched alkyl groups such as a residue obtained by removing a hydroxyl group from an oxo alcohol obtained from the above.

The polymer (A1) preferably further contains an ester compound (a3) of a monovalent aliphatic alcohol having 1 to 3 carbon atoms and (meth) acrylic acid.

Examples of the monovalent aliphatic alcohol having 1 to 3 carbon atoms constituting the ester compound (a3) include methanol, ethanol, 1-propanol and 2-propanol.

The content of the ester compound (a3) is preferably 10 to 60% by mass, and preferably 15 to 55% by mass based on the total mass of the polymer (A1) from the viewpoint of suppressing volume change of the negative electrode active material. More preferably, it is more preferably 20 to 50% by mass.

The polymer (A1) may further contain an anionic monomer salt (a4) having a polymerizable unsaturated double bond and an anionic group.

Examples of the structure having a polymerizable unsaturated double bond include a vinyl group, an allyl group, a styryl group, and a (meth) acryloyl group. The (meth) acryloyl group means an acryloyl group and / or a methacryloyl group.

Examples of the anionic group include a sulfonic acid group and a carboxyl group.

An anionic monomer having a polymerizable unsaturated double bond and an anionic group is a compound obtained by a combination thereof, such as vinyl sulfonic acid, allyl sulfonic acid, styrene sulfonic acid and (meth) acrylic acid. It is done.

Examples of the cation constituting the salt (a4) of the anionic monomer include lithium ion, sodium ion, potassium ion and ammonium ion.

When the anionic monomer salt (a4) is contained, the content thereof is preferably 0.1 to 15% by mass based on the total mass of the polymer compound from the viewpoint of internal resistance and the like. It is more preferably ˜15% by mass, and further preferably 2-10% by mass.

The polymer (A1) preferably contains (meth) acrylic acid (a11) and an ester compound (a21), and more preferably contains an ester compound (a3).

Particularly preferably, methacrylic acid is used as (meth) acrylic acid (a11), 2-ethylhexyl methacrylate is used as ester compound (a21), and methyl methacrylate is used as ester compound (a3). Methacrylic acid, 2-ethylhexyl A copolymer of methacrylate and methyl methacrylate.

The polymer compound is (meth) acrylic acid (a11), the above-described monomer (a2), an ester compound (a3) of a monovalent aliphatic alcohol having 1 to 3 carbon atoms and (meth) acrylic acid, and if necessary. A monomer composition comprising a salt (a4) of an anionic monomer having a polymerizable unsaturated double bond and an anionic group is polymerized to produce the monomer (a2) and the (meth) acrylic. The mass ratio of the acid (a11) [the monomer (a2) / the (meth) acrylic acid (a11)] is preferably 10/90 to 90/10. When the mass ratio of the monomer (a2) and the (meth) acrylic acid (a11) is 10/90 to 90/10, the polymer obtained by polymerizing the monomer has good adhesion to the carbon-based negative electrode active material. It becomes difficult to peel. The mass ratio is preferably 20/80 to 80/20, more preferably 30/70 to 85/15, and still more preferably 40/60 to 70/30.

The monomer constituting the polymer (A1) includes a monomer (a1) having a carboxyl group or an acid anhydride group, a monomer (a2) represented by the above general formula (1), a carbon number of 1 to 3 In addition to the ester compound (a3) of a monovalent aliphatic alcohol of (meth) acrylic acid and an anionic monomer salt (a4) having a polymerizable unsaturated double bond and an anionic group, As long as the physical properties of the coalescence (A1) are not impaired, the monomer (a1), the monomer (a2) represented by the general formula (1), a monovalent aliphatic alcohol having 1 to 3 carbon atoms and (meth) acrylic A radical polymerizable monomer (a5) that can be copolymerized with the ester compound (a3) with an acid may be contained.

The radical polymerizable monomer (a5) is preferably a monomer not containing active hydrogen, and the following monomers (a51) to (a58) can be used.

(A51) Hydrocarbons formed from (meth) acrylic acid and straight chain aliphatic monools having 13 to 20 carbon atoms, alicyclic monools having 5 to 20 carbon atoms, or araliphatic monools having 7 to 20 carbon atoms Carbyl (meth) acrylate As the monool, (i) linear aliphatic monool (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 Can be mentioned.

(A52) Poly (n = 2 to 30) oxyalkylene (carbon number 2 to 4) alkyl (carbon number 1 to 18) ether (meth) acrylate [methanol ethylene oxide (hereinafter abbreviated as EO) 10 mol adduct (meta ) Acrylate, propylene oxide of methanol (hereinafter abbreviated as PO), 10 mol adduct (meth) acrylate, etc.].

(A53) Nitrogen-containing vinyl compound (a53-1) Amide group-containing vinyl compound (i) (Meth) acrylamide compound having 3 to 30 carbon atoms, such as N, N-dialkyl (1 to 6 carbon atoms) or diaralkyl (carbon number) 7 to 15) (meth) acrylamide (N, N-dimethylacrylamide, N, N-dibenzylacrylamide, etc.), diacetone acrylamide (ii) Contains amide group having 4 to 20 carbon atoms excluding the above (meth) acrylamide compound Vinyl compounds such as N-methyl-N-vinylacetamide, cyclic amides [pyrrolidone compounds (having 6 to 13 carbon atoms, such as N-vinylpyrrolidone)]
(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 {quaternary amino group-containing (meth) acrylate [N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, etc.]] (Quaternized with a quaternizing agent such as methyl chloride, dimethyl sulfate, benzyl chloride, dimethyl carbonate, etc.)}
(A53-3) Heterocycle-containing vinyl compound Pyridine compound (carbon number 7 to 14, for example, 2- or 4-vinylpyridine), imidazole compound (carbon number 5 to 12, for example, N-vinylimidazole), pyrrole compound (carbon number) 6 to 13, for example, N-vinylpyrrole), pyrrolidone compound (6 to 13 carbon atoms, for example, N-vinyl-2-pyrrolidone)
(A53-4) Nitrile group-containing vinyl compound A nitrile group-containing vinyl compound having 3 to 15 carbon atoms, such as (meth) acrylonitrile, cyanostyrene, cyanoalkyl (1 to 4 carbon atoms) acrylate (a53-5) other nitrogen-containing compounds Vinyl compound A nitro group-containing vinyl compound (8 to 16, for example, nitrostyrene).

(A54) Vinyl hydrocarbon (a54-1) Aliphatic vinyl hydrocarbon An olefin 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) Alicyclic vinyl hydrocarbons 18 or more cyclic unsaturated compounds such as cycloalkenes (eg cyclohexene), (di) cycloalkadiene [eg (di) cyclopentadiene], terpenes (eg pinene and limonene), indene (a54-3) aromatic vinyl Hydrocarbons Aromatic unsaturated compounds having 8 to 20 or more carbon atoms, eg If styrene, alpha-methyl styrene, vinyl toluene, 2,4-dimethylstyrene, ethylstyrene, isopropyl styrene, butyl styrene, phenyl styrene, cyclohexyl styrene, benzyl styrene.

(A55) Vinyl ester Aliphatic vinyl ester [C4-15, for example, alkenyl ester of aliphatic carboxylic acid (mono- or dicarboxylic acid) (for example, vinyl acetate, vinyl propionate, vinyl butyrate, diallyl adipate, isopropenyl acetate, Vinyl methoxyacetate)], aromatic vinyl ester [carbon number 9-20, for example, alkenyl ester of aromatic carboxylic acid (mono- or dicarboxylic acid) (for example, vinyl benzoate, diallyl phthalate, methyl-4-vinyl benzoate), aliphatic Aromatic ring-containing esters of carboxylic acids (eg acetoxystyrene)].

(A56) Vinyl ether Aliphatic vinyl ether [C3-15, such as vinyl alkyl (C1-10) ether (vinyl methyl ether, vinyl butyl ether, vinyl 2-ethylhexyl ether, etc.), vinyl alkoxy (C1-6) Alkyl (1 to 4 carbon atoms) ether (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 (2-6 carbon atoms) (diallyloxyethane, triaryloxyethane, tetraallyloxybutane, tetrametaallyloxyethane, etc.)] Aromatic vinyl ethers (8-20 carbon atoms, eg vinyl phenyl ether) , Phenoxy styrene).

(A57) Vinyl ketone Aliphatic vinyl ketone (having 4 to 25 carbon atoms, such as vinyl methyl ketone, vinyl ethyl ketone) and aromatic vinyl ketone (having 9 to 21 carbon atoms, such as vinyl phenyl ketone).

(A58) Unsaturated dicarboxylic acid diester Unsaturated dicarboxylic acid diester having 4 to 34 carbon atoms such as dialkyl fumarate (two alkyl groups are linear, branched or alicyclic groups having 1 to 22 carbon atoms) ), Dialkyl maleate (two alkyl groups are linear, branched or alicyclic groups having 1 to 22 carbon atoms).

Of those exemplified as (a5) above, (a51), (a52) and (a53) are preferable from the viewpoint of withstand voltage.

In the polymer (A1), a monomer (a1) having a carboxyl group or an acid anhydride group, a monomer (a2) represented by the general formula (1), a monovalent aliphatic alcohol having 1 to 3 carbon atoms and ( The content of the ester compound (a3) with meth) acrylic acid, the salt (a4) of the anionic monomer having a polymerizable unsaturated double bond and an anionic group, and the radical polymerizable monomer (a5) (A1) is 0.1 to 80% by mass, (a2) is 0.1 to 99.9% by mass, (a3) is 0 to 60% by mass, and (a4) is based on the mass of the combined (A1). The content is preferably 0 to 15% by mass and (a5) is preferably 0 to 99.8% by mass. When the content of the monomer is within the above range, the liquid absorptivity to the non-aqueous electrolyte is good.

The preferable lower limit of the number average molecular weight of the polymer (A1) is 3,000, more preferably 50,000, still more preferably 60,000, and the preferable upper limit is 2,000,000, more preferably 1,500, 000, more preferably 1,000,000, particularly preferably 120,000.

The number average molecular weight of the polymer (A1) 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 Reference material: Polystyrene detector: RI
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 (A1) is a known polymerization initiator {azo initiator [2,2′-azobis (2-methylpropionitrile), 2,2′-azobis (2-methylbutyronitrile), 2, 2′-azobis (2,4-dimethylvaleronitrile, etc.)], peroxide-based initiators (benzoyl peroxide, di-t-butyl peroxide, lauryl peroxide, etc.), etc.} (Bulk polymerization, solution polymerization, emulsion polymerization, suspension polymerization, etc.).

The use amount of the polymerization initiator is preferably 0.01 to 5% by mass, more preferably 0.05 to 2% by mass, based on the total mass of the monomers, from the viewpoint of adjusting the number average molecular weight within a preferable range. More preferably, the content is 0.1 to 1.5% by mass. The polymerization temperature and polymerization time are adjusted according to the type of the polymerization initiator, etc., but the polymerization temperature is preferably −5 to 150 ° C. (more preferably 30 to 120 ° C.), and the reaction time is preferably 0.1 to It is carried out for 50 hours (more preferably 2 to 24 hours).

Examples of the solvent used in the 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 carbon atoms). Examples thereof include 4 to 8, such as n-butane, cyclohexane and toluene, ketones (having 3 to 9 carbon atoms such as methyl ethyl ketone) and amide compounds (such as N, N-dimethylformamide). From the viewpoint of adjusting the number average molecular weight within a preferable range, the amount used is preferably 5 to 900% by mass, more preferably 10 to 400% by mass, and still more preferably 30 to 300% by mass based on the total mass of the monomers. The monomer concentration is preferably 10 to 95% by mass, more preferably 20 to 90% by mass, and still more preferably 30 to 80% by mass.

Examples of the dispersion medium in emulsion polymerization and suspension polymerization include water, alcohol (for example, ethanol), ester (for example, ethyl propionate), light naphtha and the like, and examples of the emulsifier include higher fatty acid (carbon number 10 to 24) metal salt. (For example, sodium oleate and sodium stearate), higher alcohol (10 to 24 carbon atoms) sulfate metal salt (for example, sodium lauryl sulfate), ethoxylated tetramethyldecynediol, sodium sulfoethyl methacrylate, dimethylaminomethyl methacrylate, etc. Is mentioned. Furthermore, you may add polyvinyl alcohol, polyvinylpyrrolidone, etc. as a stabilizer.

The monomer concentration of the solution or dispersion is preferably 5 to 95% by mass, more preferably 10 to 90% by mass, and still more preferably 15 to 85% by mass. The amount of the polymerization initiator used is based on the total mass of the monomers. It is preferably 0.01 to 5% by mass, more preferably 0.05 to 2% by mass.

In the polymerization, known chain transfer agents such as mercapto compounds (such as dodecyl mercaptan and n-butyl mercaptan) and / or halogenated hydrocarbons (such as carbon tetrachloride, carbon tetrabromide and benzyl chloride) can be used. .

The polymer (A1) contained in the acrylic resin is a crosslinking agent (A ′) having a reactive functional group that reacts the polymer (A1) with a carboxyl group {preferably a polyepoxy compound (a′1) [polyglycidyl ether]. (Bisphenol A diglycidyl ether, propylene glycol diglycidyl ether, glycerin triglycidyl ether, etc.) and polyglycidylamine (N, N-diglycidylaniline and 1,3-bis (N, N-diglycidylaminomethyl)), etc.] And / or a crosslinked polymer formed by crosslinking with a polyol compound (a′2) (ethylene glycol or the like)}.

Examples of the method of crosslinking the polymer (A1) using the crosslinking agent (A ′) include a method of crosslinking after coating the carbon-based negative electrode active material with the polymer (A1). Specifically, the carbon-based negative electrode active material in which the carbon-based negative electrode active material is coated with the polymer (A1) by mixing and removing the solvent containing the carbon-based negative electrode active material and the polymer (A1). Then, a solution containing the crosslinking agent (A ′) is mixed with the carbon-based coated negative electrode active material and heated to cause solvent removal and a crosslinking reaction, so that the polymer (A1) becomes a crosslinking agent ( A method of causing a reaction that is crosslinked by A ′) to become a polymer compound on the surface of the carbon-based negative electrode active material may be mentioned.

The heating temperature is adjusted according to the type of the crosslinking agent, but when the polyepoxy compound (a′1) is used as the crosslinking agent, it is preferably 70 ° C. or higher, and when the polyol compound (a′2) is used. Preferably it is 120 degreeC or more.

The negative electrode coating layer preferably further contains a conductive additive. The conductive auxiliary agent is selected from conductive materials. Specifically, carbon [graphite and carbon black (acetylene black, ketjen black (registered trademark), furnace black, channel black, thermal lamp black, etc.), etc.] Carbon fibers such as PAN-based carbon fibers and pitch-based carbon fibers, carbon nanofibers and carbon nanotubes, metals [nickel, aluminum, stainless steel (SUS), silver, copper, titanium, etc.] can be used. These conductive assistants may be used alone or in combination of two or more. Alternatively, an alloy or metal oxide containing the above metal may be used. From the viewpoint of electrical stability, aluminum, stainless steel, carbon, silver, copper, titanium and a mixture thereof are preferable, silver, aluminum, stainless steel and carbon are more preferable, and carbon is more preferable. Moreover, as these conductive support agents, the thing which coated the electroconductive material (metal thing among the above-mentioned conductive support agents) by plating etc. around the particulate ceramic material or the resin material may be used. Polypropylene resin kneaded with graphene is also preferable as a conductive aid.

The average particle size of the conductive auxiliary agent is not particularly limited, but is preferably 0.01 to 10 μm and preferably 0.02 to 5 μm from the viewpoint of the electrical characteristics of the negative electrode for a lithium ion battery. More preferably, it is 0.03 to 1 μm. In addition, in this specification, the particle diameter of a conductive support agent means the largest distance L among the distances between arbitrary two points on the outline of the particle | grains which a conductive support agent forms. The value of the “average particle size of the conductive additive” is the particle size of particles observed in several to several tens of fields using an observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). The value calculated as the average value of is assumed to be adopted.

The shape (form) of the conductive auxiliary agent is not limited to the particle form, and may be a form other than the particle form, for example, a fibrous conductive auxiliary agent.

Fibrous conductive assistants include conductive fibers in which synthetically conductive metals and graphite are uniformly dispersed in synthetic fibers, metal fibers made from metal such as stainless steel, and the surface of organic fibers. Examples thereof include conductive fibers coated with metal, and conductive fibers whose organic surface is coated with a resin containing a conductive substance. The average fiber diameter of the fibrous conductive additive is preferably 0.1 to 30 μm, and more preferably 0.1 to 20 μm.

When the negative electrode coating layer contains a conductive auxiliary, the mass of the conductive auxiliary contained in the negative electrode coating layer is 15 to 75% by mass with respect to the total mass of the polymer compound as the coating resin and the conductive auxiliary. It is preferable that

When the negative electrode coating layer of the carbon-based coated negative electrode active material contains a conductive additive, the conductivity contained in the negative electrode coating layer even when the SEI film is formed on the surface of the carbon-based negative electrode active material after precharging. The conduction path between the active materials can be maintained by the effect of the auxiliary agent, and the increase in resistance due to the formation of the SEI film can be suppressed, and it is more preferable that the ratio of the conductive auxiliary agent is within this range because the resistance can be easily suppressed. .

The negative electrode active material composition constituting the negative electrode active material layer may contain a conductive material in addition to the above-mentioned conductive aid. It is preferable that the negative electrode active material layer contains a conductive material because a conductive path between the active materials can be easily maintained. As the conductive material, the same materials as the conductive auxiliary agent can be used, and preferable materials are also the same.

When the negative electrode active material layer contains a conductive material, the ratio of the mass of the conductive material to the mass of the negative electrode active material is not particularly limited, but is preferably 0 to 10% by mass.

The negative electrode for a lithium ion battery of the present invention preferably has a negative electrode active material layer provided on a negative electrode current collector.

Examples of the material constituting the negative electrode current collector include metal materials such as copper, aluminum, titanium, stainless steel, nickel, and alloys thereof. Among these, copper is preferable from the viewpoints of weight reduction, corrosion resistance, and high conductivity. The negative electrode current collector may be a current collector made of baked carbon, conductive polymer, conductive glass, or the like, or may be a resin current collector made of a conductive agent and a resin.

The shape of the negative electrode current collector is not particularly limited, and may be a sheet-like current collector made of the above material and a deposited layer made of fine particles made of the above material.

The thickness of the negative electrode current collector is not particularly limited, but is preferably 50 to 500 μm.

As the conductive agent constituting the resin current collector, the same conductive material as an optional component of the negative electrode active material layer can be suitably used.

The resin constituting the resin current collector includes polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), polycycloolefin (PCO), polyethylene terephthalate (PET), polyether nitrile (PEN), polytetra Fluoroethylene (PTFE), styrene butadiene rubber (SBR), polyacrylonitrile (PAN), polymethyl acrylate (PMA), polymethyl methacrylate (PMMA), polyvinylidene fluoride (PVdF), epoxy resin, silicone resin or a mixture thereof Is mentioned. From the viewpoint of electrical stability, polyethylene (PE), polypropylene (PP), polymethylpentene (PMP) and polycycloolefin (PCO) are preferable, and polyethylene (PE), polypropylene (PP) and polymethylpentene are more preferable. (PMP).

Hereinafter, the manufacturing method of the negative electrode for lithium ion batteries of this invention is demonstrated.

The method for producing a negative electrode for a lithium ion battery according to the present invention is applied on a current collector or separator using a slurry containing a negative electrode active material composition containing a silicon-based negative electrode active material and a carbon-based negative electrode active material, and a dispersion medium. Forming a film. The manufacturing method includes a step of doping a lithium-based negative electrode active material with lithium ions before or after a step of forming a coating film and before assembling a lithium-ion battery, and a step of doping lithium ions into a carbon-based negative electrode active material. Including the step of. And it has the characteristics in the point which does not contain the process of drying a coating film substantially.

Note that the order of the above steps is not particularly limited. For example, the step of doping a lithium ion into a silicon-based negative electrode active material and the step of doping lithium ions into a carbon-based negative electrode active material may be performed simultaneously or separately, and then a step of forming a coating film may be performed. Alternatively, after the step of forming the coating film, the step of doping the silicon-based negative electrode active material with lithium ions and the step of doping the carbon-based negative electrode active material with lithium ions may be performed simultaneously. That is, the silicon-based negative electrode active material and the carbon-based negative electrode active material contained in the slurry may be a silicon-based negative electrode active material and a carbon-based negative electrode active material before being doped with lithium ions, or doped with lithium ions. It may be a later silicon-based negative electrode active material and carbon-based negative electrode active material.

Further, after the step of doping lithium ions into the silicon-based negative electrode active material, a step of forming a coating film may be performed, and then the step of doping lithium ions into the carbon-based negative electrode active material may be performed; It is also possible to perform a step of forming a coating film after the step of doping the active material with lithium ions, and then perform a step of doping lithium ions into the silicon-based negative electrode active material.

In any case, the step of forming a coating film, the step of doping lithium ions into the silicon-based negative electrode active material, and the step of doping lithium ions into the carbon-based negative electrode active material are performed in a lithium ion battery (according to the present invention). It is essential to be performed before the assembly of the lithium ion battery to which the negative electrode for lithium ion battery is applied.

Specific examples of the embodiment include the following four embodiments.

(First embodiment)
A mode in which a step of doping a lithium-based negative electrode active material with lithium ions and a step of doping lithium ions are performed simultaneously.

(Second Embodiment)
The silicon-based negative electrode active material and the carbon-based negative electrode active material are separately doped with lithium ions, and the lithium-doped silicon-based negative electrode active material and the lithium-ion-doped carbon-based negative electrode active material A form further comprising a step of mixing the substances.

(Third embodiment)
The step of doping lithium ions into the carbon-based negative electrode active material is a step of doping lithium ions into the carbon-based negative electrode active material contained in the mixture of the carbon-based negative electrode active material and the silicon-based negative electrode active material doped with lithium ions. Some form.

(Fourth embodiment)
The step of doping lithium ions into the silicon-based negative electrode active material is a step of doping lithium ions into the silicon-based negative electrode active material contained in the mixture of the silicon-based negative electrode active material and the carbon-based negative electrode active material doped with lithium ions. Some form.

Each of the above embodiments will be described below.

(First embodiment)
In the first embodiment, lithium ions are simultaneously doped into a mixed active material including a silicon-based negative electrode active material and a carbon-based negative electrode active material. Specifically, a precharge negative electrode having a negative electrode active material layer including a silicon-based negative electrode active material and a carbon-based negative electrode active material is prepared, and a precharge battery including a precharge negative electrode and a precharge positive electrode is provided. Examples thereof include a method of pre-charging the battery for pre-charging and a method of doping lithium ions by bringing a lithium ion source into contact with the mixed active material in the raw slurry. First, an example of a method for pre-charging the pre-charging battery will be described in the following (3-1) to (3-3).

(3-1-a) As an example of a method for producing a negative electrode for precharging, a raw material slurry is applied on a film, and pressurized or depressurized to obtain a silicon-based negative electrode active material and a carbon-based negative electrode active material (that is, A method of preparing a negative electrode for precharging by fixing the mixed active material) on the film can be mentioned. The raw slurry is a mixture of a mixed active material and a dispersion medium.

Examples of the dispersion medium contained in the raw material slurry include an electrolytic solution and a non-aqueous solvent. In these, electrolyte solution is preferable. That is, the raw material slurry is preferably an electrolytic solution slurry containing a particulate mixed active material and an electrolytic solution. As the electrolytic solution, a nonaqueous electrolytic solution containing an electrolyte and a nonaqueous solvent, which is used in the manufacture of a lithium ion battery, can be used.

As the electrolyte contained in the electrolytic solution, those used in known electrolytic solutions can be used, for example, lithium salt electrolytes of inorganic acids such as LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ and LiClO _4. , Sulfonylimide-based electrolytes having fluorine atoms such as LiN (FSO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ and LiN (C ₂ F ₅ SO ₂ ) ₂ , fluorine atoms such as LiC (CF ₃ SO ₂ ) ₃ Sulfonylmethide-based electrolytes having

As the nonaqueous solvent contained in the electrolytic solution, those used in known electrolytic solutions can be used, for example, lactone compounds, cyclic or chain carbonates, chain carboxylates, cyclic or chain ethers. , Phosphate esters, nitrile compounds, amide compounds, sulfones, sulfolanes, and the like, and mixtures thereof. A non-aqueous solvent may be used individually by 1 type, and may use 2 or more types together.

Examples of the lactone compound include 5-membered rings (such as γ-butyrolactone and γ-valerolactone) and 6-membered lactone compounds (such as δ-valerolactone). Examples of the cyclic carbonate include propylene carbonate, ethylene carbonate and butylene carbonate. Examples of the chain carbonate include dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl-n-propyl carbonate, ethyl-n-propyl carbonate, and di-n-propyl carbonate. Examples of chain carboxylic acid esters include methyl acetate, ethyl acetate, propyl acetate, and methyl propionate. Examples of the cyclic ether include tetrahydrofuran, tetrahydropyran, 1,3-dioxolane, 1,4-dioxane and the like. Examples of the chain ether include dimethoxymethane and 1,2-dimethoxyethane. Examples of phosphate esters include trimethyl phosphate, triethyl phosphate, ethyl dimethyl phosphate, diethyl methyl phosphate, tripropyl phosphate, tributyl phosphate, tri (trifluoromethyl) phosphate, tri (trichloromethyl) phosphate, Tri (trifluoroethyl) phosphate, tri (triperfluoroethyl) phosphate, 2-ethoxy-1,3,2-dioxaphosphoran-2-one, 2-trifluoroethoxy-1,3,2- Examples include dioxaphospholan-2-one and 2-methoxyethoxy-1,3,2-dioxaphosphoran-2-one. Examples of the nitrile compound include acetonitrile. Examples of the amide compound include N, N-dimethylformamide (hereinafter also referred to as DMF). Examples of the sulfone include chain sulfones such as dimethyl sulfone and diethyl sulfone, and cyclic sulfones such as sulfolane.

Among nonaqueous solvents, lactone compounds, cyclic carbonates, chain carbonates, and phosphates are preferable from the viewpoint of battery output and charge / discharge cycle characteristics. More preferred are lactone compounds, cyclic carbonates and chain carbonates, and particularly preferred are cyclic carbonates and a mixture of cyclic carbonates and chain carbonates. Most preferred is a mixture of ethylene carbonate (EC) and propylene carbonate (PC), a mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC), or a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC). It is.

The electrolyte concentration of the non-aqueous electrolyte is not particularly limited, but is preferably 0.5 to 5 mol / L, and preferably 0.8 to 3 mol / L from the viewpoint of the handleability of the electrolyte and the battery capacity. Is more preferably 1 to 2 mol / L.

The non-aqueous solvent used as the dispersion medium contained in the raw slurry can be the same as the non-aqueous solvent contained in the electrolytic solution.

The membrane is preferably a membrane capable of separating the mixed active material and the dispersion medium in the subsequent pressurization or decompression. Further, it is preferable that the film is made of a highly conductive material (conductive material) because the film can be used instead of the current collector, and even if the current collector is in contact with the film, the conductivity is not hindered. For example, a material having an electric conductivity of 100 mS / cm or more can be preferably used. Examples of materials having such characteristics include filter papers, metal meshes and the like in which conductive fibers such as carbon fibers are blended.

As the metal mesh, it is preferable to use a stainless steel mesh, for example, a SUS316 twilled woven wire mesh (manufactured by Sunnet Kogyo) and the like. The mesh opening of the metal mesh is preferably set so that the active material particles and the conductive member do not pass through, for example, a 2300 mesh mesh is preferably used.

The raw material slurry can be applied onto the film using an arbitrary coating apparatus such as a bar coater or a brush.

Subsequently, the mixed active material is fixed on the film by applying pressure or reduced pressure. As a method of the pressurizing operation, a method of pressing using a press machine from above the coating surface of the raw slurry can be mentioned. Moreover, as a method of pressure reduction operation, a method of applying a filter paper or a mesh or the like to the surface of the membrane on which the raw material slurry is not applied and sucking with a vacuum pump can be mentioned. The dispersion medium is removed from the raw slurry by pressurization or decompression, and the mixed active material is fixed on the film.

As described above, when the film is made of a conductive material, the film can be used as a current collector, or the current collector and the film can be brought into contact with each other to function as a single current collector. Further, when the film is a material that does not have conductivity, the film may be disposed on the separator side. The membrane may be a separator. Examples of the film made of a material having no conductivity include an aramid separator (manufactured by Japan Vilene Co., Ltd.). When the dispersion medium is an electrolytic solution, the membrane is a membrane that allows the electrolytic solution to permeate without permeating the mixed active material, and only the electrolytic solution may be permeated through the membrane by pressurization or decompression.

Further, after pressurization or decompression, the raw material slurry may be pressurized with a stronger pressure. This step (also referred to as a pressing step) is a step of increasing the density of the mixed active material by further increasing the pressure difference as compared with the pressurizing or depressurizing step described above. The pressing step includes both an aspect in which pressurization is performed after the pressure reduction process and an aspect in which the pressure to be pressurized after the pressurization process is further increased.

Furthermore, a step of transferring the precharging negative electrode fixed on the film to the main surface of the current collector or the separator may be performed. In this case, it is preferable to transfer the main surface of the precharge negative electrode on the side opposite to the membrane in contact with the main surface of the current collector or separator. When the film is made of a conductive material and the film is used in place of the current collector, it is preferable to transfer the main surface opposite to the film in contact with the main surface of the separator. Moreover, when not using a film | membrane as a collector, it is preferable to perform the process of peeling a film | membrane after transcription | transfer.

(3-1-b) The preparation of the negative electrode for precharging can also be performed by the following method. That is, a step of applying a raw material slurry on a current collector to form a slurry layer on the current collector, and placing a separator on the slurry layer, absorbing liquid from the upper surface side of the separator, and mixing A step of fixing an active material between the current collector and the separator.

First, a raw material slurry containing a mixed active material is applied on a current collector to form a slurry layer. Examples of the current collector include aluminum, copper, aluminum, titanium, stainless steel, nickel, baked carbon, conductive polymer, and conductive glass. As the slurry, the same slurry as the raw material slurry can be used. A conductive fiber as a conductive member may be further added to the slurry to disperse the conductive fiber in the slurry. The slurry is preferably an electrolyte slurry containing an electrolyte. As the electrolytic solution, the same electrolyte solution slurry as described above can be used. The slurry may be a solvent slurry containing a solvent. The slurry can be applied onto the current collector using an arbitrary coating apparatus such as a bar coater or a brush.

Subsequently, a separator is placed on the slurry layer, and liquid is absorbed from the upper surface side of the separator, so that the mixed active material is fixed between the current collector and the separator. First, a separator is placed on the slurry layer. And it absorbs from the upper surface side of a separator. As the separator, an aramid separator (manufactured by Japan Vilene Co., Ltd.), a polyethylene, a microporous film made of a polypropylene film, a multilayer film of a porous polyethylene film and polypropylene, a polyester fiber, an aramid fiber, a non-woven fabric made of glass fiber, and the like, and Those having ceramic fine particles such as silica, alumina and titania attached to the surface thereof can be mentioned.

The liquid absorption may be performed by sucking the liquid that has been pressed from the upper surface side or the lower surface side of the separator and leached out from the upper surface of the separator, or by sucking the liquid by reducing the pressure from the upper surface side of the separator. May be performed. Furthermore, liquid absorption from the upper surface side of the separator may be performed by placing a liquid absorbing material on the upper surface of the separator. As the liquid-absorbing material, a liquid-absorbing cloth such as towel, paper, liquid-absorbing resin, or the like can be used. The electrolyte solution or the solvent is removed from the slurry by the liquid absorption, and the mixed active material is fixed between the current collector and the separator, and the shape is maintained so loose that it does not flow. Although the method of pressurization is not particularly limited, it can be carried out by various methods. For example, a method using a known press machine and a method of applying pressure by placing a heavy object or the like as a weight may be mentioned, and the pressurization may be performed while vibrating with an ultrasonic vibrator or the like. Pressure when pressurized from the upper side or the lower side of the separator is preferably 0.8 ~ 41kg / cm ^2, more preferably 0.9 ~ 10kg / cm ^2. When the pressure is within this range, it is preferable because the capacity of the battery can be increased.

In the negative electrode for precharging manufactured in this way, the first main surface of the negative electrode for precharging is in contact with the separator, and the second main surface of the negative electrode for precharging is in contact with the current collector. In such a method for producing a precharge negative electrode, the electrode is produced in a state where the electrode is sandwiched between a separator and a current collector. Therefore, it is not necessary to separately perform a step of disposing a separator and a current collector on both sides of the electrode, and this is preferable because the number of electrodes in a preferable form as a bipolar electrode can be obtained with a small number of steps.

(3-2) Next, a precharge battery including a precharge negative electrode and a precharge positive electrode is fabricated. For example, a preliminary charging battery can be obtained by combining a negative electrode for preliminary charging with a positive electrode for preliminary charging that serves as a counter electrode, storing the separator together with a separator in a cell container, injecting an electrolyte, and sealing the cell container. Also, a positive electrode for precharging is formed on one surface of the current collector, a negative electrode for precharging is formed on the other surface to produce a bipolar electrode, and the bipolar electrode is laminated with a separator to form a cell container. A battery for preliminary charging can also be obtained by storing, injecting an electrolyte, and sealing the cell container.

As the positive electrode for precharging, a positive electrode having a positive electrode active material or a metal lithium electrode can be used. However, since the positive electrode active material is expensive, it is preferable to use a metal lithium electrode. In the case of using a positive electrode having a positive electrode active material, the positive electrode having a positive electrode active material can be produced by applying the positive electrode active material to a current collector using a binder (binder) and drying it. Examples of the positive electrode active material include a composite oxide of lithium and a transition metal (for example, LiCoO ₂ , LiNiO ₂ , LiMnO _2, and LiMn ₂ O ₄ ), a phosphate of lithium and a transition metal (for example, LiFePO ₄ ), and the like. . In addition, as a binder, what was mentioned as a binder which a negative electrode active material layer does not contain in this specification is mentioned. Examples of the current collector include copper, aluminum, titanium, stainless steel, nickel, baked carbon, conductive polymer, and conductive glass. As a separator, the separator mentioned above can be used as a separator which can be used for preparation of the negative electrode for precharge. As the electrolytic solution, the electrolytic solution described above as the electrolytic solution contained in the raw material slurry can be used.

(3-3) Precharge the battery for precharging. Thereby, lithium ion can be simultaneously doped with respect to the mixed active material containing a silicon-type negative electrode active material and a carbon-type negative electrode active material. Although the method of preliminary charging is not particularly limited, a method of charging and discharging one cycle with respect to the preliminary charging battery is preferable. By the above method, a silicon-based negative electrode active material doped with lithium ions and a carbon-based negative electrode active material doped with lithium ions can be obtained.

Using a silicon-based negative electrode active material doped with lithium ions and a carbon-based negative electrode active material doped with lithium ions (also referred to as a mixed active material doped with lithium ions), the negative electrode for lithium-ion batteries of the present invention Examples of the method for manufacturing the following include the following methods.

The precharge battery is disassembled, the mixed active material doped with lithium ions is taken out, and a slurry (dispersion) dispersed at a concentration of 30 to 60% by mass based on the mass of the solvent is placed on the negative electrode current collector. After coating with a coating device such as a coater, the solvent is removed by a method of allowing the nonwoven fabric to stand on the surface and absorbing the liquid, a method of pressurizing or depressurizing, and pressing with a press if necessary. The negative electrode active material layer need not be formed directly on the negative electrode current collector. For example, a layered material (negative electrode active material layer) obtained by applying the slurry to the surface of an aramid separator or the like and removing the solvent is used. The negative electrode for lithium ion batteries of the present invention can also be produced by laminating on the negative electrode current collector. As the solvent for dispersing the mixed active material doped with lithium ions, it is preferable to use an electrolytic solution, and the electrolytic solution can be the same as that used for the above-described electrolytic slurry.

Moreover, the negative electrode for preliminary charging, which is disassembled and removed from the battery for preliminary charging, can be used as the negative electrode for lithium ion batteries.

(Second Embodiment)
In the second embodiment, lithium ions are doped into each of the silicon-based negative electrode active material and the carbon-based negative electrode active material. Instead of the “mixed active material” in the first embodiment, a raw material slurry containing only a silicon-based negative electrode active material and a raw material slurry containing only a carbon-based negative electrode active material are prepared. Then, using the same method as in the first embodiment, each of the silicon-based negative electrode active material and the carbon-based negative electrode active material contained in the raw slurry is doped with lithium ions. Then, a silicon-based negative electrode active material doped with lithium ions and a carbon-based negative electrode active material doped with lithium ions are prepared separately.

When a lithium-doped silicon-based negative electrode active material and a lithium-ion-doped carbon-based negative electrode active material are respectively obtained in a precharge battery, the precharge battery is disassembled for precharge. After removing the negative electrode, a dispersion medium is added to the silicon-based negative electrode active material and the carbon-based negative electrode active material fixed on the negative electrode for precharging to make a slurry again. Then, a slurry containing a silicon-based negative electrode active material doped with lithium ions and a slurry containing a carbon-based negative electrode active material doped with lithium ions are obtained, and by mixing these two slurries, lithium ions are doped. A mixed slurry containing the silicon-based negative electrode active material and the carbon-based negative electrode active material doped with lithium ions is obtained. Note that a dispersion medium may be added to a mixture of the silicon-based negative electrode active material and the carbon-based negative electrode active material fixed on the preliminary charging negative electrode to form a mixed slurry. Using this mixed slurry, a negative electrode for a lithium ion battery can be produced.

(Third embodiment)
In the third embodiment, first, lithium ions are doped only into the silicon-based negative electrode active material. Instead of the “mixed active material” in the first embodiment, a raw material slurry containing only a silicon-based negative electrode active material is prepared. Then, using the same method as in the first embodiment, the silicon-based negative electrode active material contained in the raw slurry is doped with lithium ions to produce a silicon-based negative electrode active material doped with lithium ions.

When the silicon-based negative electrode active material doped with lithium ions is obtained in the battery for precharging, the silicon-based material fixed to the negative electrode for precharging after disassembling the battery for precharging and removing the negative electrode for precharging A dispersion medium is added to the negative electrode active material to form a slurry again. Then, a slurry containing a silicon-based negative electrode active material doped with lithium ions is obtained. The slurry is mixed with a silicon-based negative electrode active material doped with lithium ions and lithium ions by mixing a carbon-based negative electrode active material not doped with lithium ions in a powder state or in a slurry state. A mixed slurry containing a carbon-based negative electrode active material is obtained. And the carbon-type negative electrode active material contained in this mixed slurry is doped with lithium ions.

(Fourth embodiment)
In the fourth embodiment, first, lithium ions are doped only into the carbon-based negative electrode active material. Instead of the “mixed active material” in the first embodiment, a raw material slurry containing only the carbon-based negative electrode active material is prepared. Then, using the same method as in the first embodiment, the carbon-based negative electrode active material contained in the raw slurry is doped with lithium ions to produce a carbon-based negative electrode active material doped with lithium ions.

When the carbon-based negative electrode active material doped with lithium ions is obtained in the battery for preliminary charging, the carbon-based material fixed on the negative electrode for preliminary charging after disassembling the preliminary charging battery and removing the negative electrode for preliminary charging. A dispersion medium is added to the negative electrode active material to form a slurry again. Then, a slurry containing a carbon-based negative electrode active material doped with lithium ions is obtained. By mixing this slurry with a silicon-based negative electrode active material not doped with lithium ions in a powdered state or in a slurry state, a carbon-based negative electrode active material doped with lithium ions and lithium ions are doped. A mixed slurry containing a non-conductive silicon-based negative electrode active material is obtained. The silicon-based negative electrode active material contained in this mixed slurry is doped with lithium ions.

Next, a process of forming a coating film on a current collector or separator using a slurry containing a negative electrode active material composition containing a silicon-based negative electrode active material and a carbon-based negative electrode active material and a dispersion medium will be described. In the present invention, lithium having a negative electrode active material layer composed of a non-binding body of a negative electrode active material composition comprising a carbon-based negative electrode active material doped with lithium ions and a silicon-based negative electrode active material doped with lithium ions. In order to obtain a negative electrode for an ion battery, it is preferable that the slurry does not substantially contain a binder. In this specification, the slurry does not substantially contain a binder. Specifically, the content of the binder is 1% by mass or less with respect to 100% by mass of the total solid content contained in the slurry. It means that. The content of the binder is more preferably 0.5% by mass or less, further preferably 0.2% by mass or less, particularly preferably 0.1% by mass or less, and most preferably 0% by mass. %.

In addition, when using the negative electrode for preliminary | backup charge after doping lithium ion as a negative electrode for lithium ion batteries, the formation process of the coating film for forming the negative electrode active material layer of the negative electrode for preliminary | backup charge corresponds to this process .

In the present invention, lithium having a negative electrode active material layer composed of a non-binding body of a negative electrode active material composition comprising a carbon-based negative electrode active material doped with lithium ions and a silicon-based negative electrode active material doped with lithium ions. In order to obtain the negative electrode for an ion battery, it is essential that the process of drying a coating film is not included substantially. In this specification, substantially not including the step of drying the coating film means that the dispersion medium (solvent) is removed so that the solid content concentration of the coating film (negative electrode active material layer) is 99% by mass or more. It means not to do. By substantially not including the step of drying the coating film, even when the binder contains the binder, the binder is solidified and the active materials and the active material particles and the current collector Is not immobilized, the non-bound state can be maintained.

In addition, the method of removing the excess dispersion medium from the slurry after coating by the above-described liquid absorption or pressurization or depressurization does not cause the solid content concentration of the coating film to be 99% by mass or more. It is not included in the process of drying the coating film.

By the above method, it has the negative electrode active material layer which consists of a non-binding body of the negative electrode active material composition containing the carbon negative electrode active material doped with lithium ions and the silicon negative electrode active material doped with lithium ions The negative electrode for lithium ion batteries of the present invention can be obtained.

In any of the embodiments, a carbon-based coated negative electrode active material may be used as the carbon-based negative electrode active material. The carbon-based coated negative electrode active material is, for example, dropped and mixed with a polymer solution containing a polymer compound over 1 to 90 minutes in a state where the carbon-based negative electrode active material is placed in a universal mixer and stirred at 30 to 50 rpm, Furthermore, it can be obtained by mixing a conductive additive as necessary, raising the temperature to 50 to 200 ° C. while stirring, reducing the pressure to 0.007 to 0.04 MPa, and holding for 10 to 150 minutes.

The blending ratio of the carbon-based negative electrode active material and the polymer compound is not particularly limited, but is preferably carbon-based negative electrode active material: polymer compound = 1: 0.001 to 0.1 by mass ratio. .

Examples of the solvent used for producing the carbon-based coated negative electrode active material include 1-methyl-2-pyrrolidone, methyl ethyl ketone, DMF, dimethylacetamide, N, N-dimethylaminopropylamine, and tetrahydrofuran.

Using the carbon-based negative electrode active material thus obtained as a carbon-based negative electrode active material, a carbon-based negative electrode active material doped with lithium ions is obtained by doping lithium ions into the carbon-based negative electrode active material. It is done. In the carbon-based coated negative electrode active material doped with lithium ions, the carbon-based negative electrode active material at the center of the carbon-based coated negative electrode active material is doped with lithium ions.

When producing a lithium ion battery using the negative electrode for a lithium ion battery of the present invention, a counter electrode is combined and housed in a cell container together with a separator, and a non-aqueous electrolyte is injected if necessary. It can be manufactured by a sealing method or the like.

Further, in the negative electrode for a lithium ion battery of the present invention in which the negative electrode active material layer is formed only on one surface of the negative electrode current collector, a positive electrode active material layer made of the positive electrode active material is formed on the other surface of the negative electrode current collector. It is also possible to produce a bipolar electrode, stack the bipolar electrode with a separator and store it in a cell container, inject a non-aqueous electrolyte if necessary, and seal the cell container.

As the electrode (positive electrode) that is the counter electrode of the negative electrode for a lithium ion battery of the present invention, a positive electrode used for a known lithium ion battery can be used. Examples of the separator and non-aqueous electrolyte include known separators for lithium-ion batteries and non-aqueous electrolytes (electrolyte and non-aqueous solvent) that can be used for the preparation of the negative electrode for precharging.

Next, the present invention will be specifically described by way of examples. However, the present invention is not limited to the examples without departing from the gist of the present invention. Unless otherwise specified, “part” means “part by mass” and “%” means “% by mass”.

<Production Example 1: Production of resin current collector>
In a twin-screw extruder, 70 parts of polypropylene [trade name “Sun Allomer PL500A”, manufactured by Sun Allomer Co., Ltd.], 25 parts of carbon nanotube [trade name: “FloTube 9000”, manufactured by CNano Co., Ltd.] “Sanyo Kasei Kogyo Co., Ltd.] 5 parts was melt kneaded at 200 ° C. and 200 rpm to obtain a resin mixture. The obtained resin mixture was passed through a T-die extrusion film forming machine and stretched and rolled to obtain a resin current collector with a film thickness of 100 μm. The resin current collector was cut into 3 cm × 3 cm, and after nickel deposition was performed on one surface, a current extraction terminal (5 mm × 3 cm) was connected.

<Production Example 2: Production of polymer compound solution for coating layer>
A 4-necked flask equipped with a stirrer, thermometer, reflux condenser, dropping funnel and nitrogen gas inlet tube was charged with 407.9 parts of DMF and heated to 75 ° C. Next, a monomer mixture containing 242.8 parts of methacrylic acid, 97.1 parts of methyl methacrylate, 242.8 parts of 2-ethylhexyl methacrylate, and 116.5 parts of DMF, and 2,2′-azobis (2,4-dimethyl) (Valeronitrile) 1.7 parts and 2,2′-azobis (2-methylbutyronitrile) 4.7 parts dissolved in DMF 58.3 parts and a four-necked flask were blown with nitrogen, Under stirring, radical polymerization was carried out by continuously dropping with a dropping funnel over 2 hours. After completion of dropping, the reaction was continued at 75 ° C. for 3 hours. Next, the temperature was raised to 80 ° C., and the reaction was continued for 3 hours to obtain a copolymer solution having a resin solid content concentration of 50 mass%. To this, 789.8 parts of DMF was added to obtain a polymer compound solution for a coating layer having a resin solid content concentration of 30% by mass.

<Production Example 3: Production of carbon-based coated negative electrode active material particles 1>
90 parts of non-graphitizable carbon powder [Carbotron (registered trademark) PS (F) manufactured by Kureha Battery Materials Japan Co., Ltd., volume average particle size 18 μm] 90 parts universal mixer high speed mixer FS25 [Earth Co., Ltd. In a state of stirring at room temperature and 150 rpm, 30 parts of the polymer compound solution for coating layer was mixed dropwise over 60 minutes so that the resin solid content was 5 parts by mass, and further stirred for 30 minutes. . Next, 5 parts of acetylene black [DENKA BLACK (registered trademark) manufactured by Denka Co., Ltd.] was mixed in 3 portions while maintaining the stirring, and the temperature was raised to 70 ° C. while stirring for 30 minutes until the pressure reached 0.01 MPa. The pressure was reduced and held for 30 minutes. By the above operation, carbon-based coated negative electrode active material particles 1 were obtained.

<Production Example 4: Preparation of carbon-based coated negative electrode active material particles 2>
The same as in Production Example 3 except that the non-graphitizable carbon powder is changed to a non-graphitizable carbon powder having a different particle size [manufactured by Kureha Battery Materials Japan, volume average particle size of 0.1 μm]. Thus, carbon-based coated negative electrode active material particles 2 were obtained.

<Production Example 5: Production of carbon-coated silicon particles>
Chemical vapor deposition of silicon particles [Sigma Aldrich Japan Co., Ltd., volume average particle size 1.5 μm] in a horizontal heating furnace and 1100 ° C./1000 Pa, average residence time of about 2 hours while venting methane gas into the horizontal heating furnace The operation was performed to obtain silicon-based negative electrode active material particles (volume average particle diameter of 1.5 μm) having a carbon amount of 2 mass% and having a surface coated with carbon.

<Production Example 6: Preparation of carbon-coated silicon oxide particles>
Silicon oxide particles [Sigma-Aldrich Japan, volume average particle size 1.5 μm] are placed in a horizontal heating furnace, and a chemical vapor deposition operation is performed at 1100 ° C./1000 Pa and an average residence time of about 2 hours while venting methane gas. Silicon-based negative electrode active material particles having a carbon content of 2% by mass and a surface coated with carbon (volume average particle diameter of 1.5 μm) were obtained.

<Production Example 7: Production of silicon composite particles>
3 parts of silicon particles [manufactured by Sigma-Aldrich Japan, volume average particle size 1.5 μm] are put into a universal mixer high speed mixer FS25 [manufactured by Earth Technica Co., Ltd.] and stirred at room temperature at 720 rpm. 10 parts of an acid resin solution (solvent: ultrapure water, solid content concentration 10%) was added dropwise over 2 minutes, and the mixture was further stirred for 5 minutes. Next, 1 part of acetylene black [Denka Co., Ltd., Denka Black (registered trademark)] was added while stirring, and stirring was continued for 30 minutes. Thereafter, the pressure was reduced to 0.01 MPa while maintaining the stirring, and then the temperature was raised to 140 ° C. while maintaining the stirring and the degree of vacuum, and the volatile matter was distilled off by maintaining the stirring, the degree of vacuum and the temperature for 8 hours. . The obtained powder was classified with a sieve having an opening of 20 μm to obtain silicon composite particles (volume average particle diameter of 30 μm).

<Production Example 8: Production of carbon fiber>
Carbon fibers, Eiichi Yasuda, Asao Oya, Shinya Komura, Shigeki Tomonoh, Takashi Nishizawa, Shinsuke Nagata, Takashi Akatsu, CARBON, 50,2012,1432-1434 and Eiichi Yasuda, Takashi Akatsu, Yasuhiro Tanabe, Kazumasa Nakamura, Yasuto Hoshikawa, It was manufactured by the following method with reference to the manufacturing method of Naoya Miyajima, TANSO, 255, 2012, pages 254 to 265. As a carbon precursor, 10 parts by mass of synthetic mesophase pitch AR · MPH [manufactured by Mitsubishi Gas Chemical Co., Ltd.] and 90 parts by mass of polymethylpentene TPX RT18 [manufactured by Mitsui Chemicals, Inc.] under a barrel temperature of 310 ° C. under a nitrogen atmosphere A resin composition was prepared by melt-kneading using a single screw extruder. The resin composition was melt-extruded and spun at 390 ° C. The spun resin composition was placed in an electric furnace and held at 270 ° C. for 3 hours under a nitrogen atmosphere to stabilize the carbon precursor. Next, the electric furnace was heated to 500 ° C. over 1 hour and held at 500 ° C. for 1 hour to decompose and remove polymethylpentene. The electric furnace was heated up to 1000 ° C. over 2 hours and held at 1000 ° C. for 30 minutes, and the remaining stabilized carbon precursor was used as a conductive fiber. 90 parts by mass of the obtained conductive fibers, 500 parts by mass of water, and 1000 parts by mass of zirconia balls having a diameter of 0.1 mm were placed in a pot mill container and pulverized for 5 minutes. The zirconia balls were classified and then dried at 100 ° C. to obtain carbon fibers. From the measurement result by SEM, the average fiber diameter of the obtained carbon fiber was 0.3 μm, the average fiber length was 26 μm (aspect ratio 87), and the electric conductivity was 600 mS / cm.

<Example 1>
[Preparation of negative electrode active material slurry]
Carbon system obtained in Production Example 3 in 90 parts of an electrolyte prepared by dissolving LiPF ₆ in a mixed solvent of ethylene carbonate (EC) and propylene carbonate (PC) (volume ratio 1: 1) at a ratio of 1 mol / L. After adding 6 parts of coated negative electrode active material particles 1, 3 parts of carbon-coated silicon particles obtained in Production Example 5, and 1 part of carbon fiber obtained in Production Example 8 as a conductive material, a planetary stirring type mixing and kneading apparatus { Awatori Nerita [Sinky Co., Ltd.]} was used and mixed at 2000 rpm for 5 minutes to prepare a negative electrode active material slurry.

[Preparation of negative electrode active material layer]
A butyl rubber sheet (hereinafter referred to as a mask) having a φ15 mm hole is stacked on a φ23 mm aramid non-woven fabric (model number 2415R: manufactured by Japan Vilene). It was dripped so that it might become 9 mg / cm < ² >. Further, a negative negative electrode active material layer having a diameter of 15 mm was produced by suction filtration (reduced pressure) from the aramid nonwoven fabric side. Subsequently, the negative electrode for precharging was produced by pressing at a pressure of 5 MPa for about 10 seconds. Using the produced precharge negative electrode, a precharge battery was prepared and precharged by the following method to produce a lithium ion battery negative electrode of the present invention.

[Preparation of battery for pre-charging]
Two copper foils (3 cm × 3 cm, thickness 17 μm) with terminals (5 mm × 3 cm) are stacked so that each terminal comes out in the same direction, and two sheets of commercially available heat-sealing aluminum laminate films (10 cm) × 8 cm), and one side where the terminal comes out was heat-sealed to produce a precharging laminate cell. The aramid non-woven fabric was peeled off from the preliminary charging negative electrode, and left on one copper foil in the preliminary charging laminate cell, and 100 μL of an electrolytic solution was added. Next, a separator (5 cm × 5 cm, thickness 23 μm, Celgard 3501 PP) was allowed to stand on the negative electrode for preliminary charging, and 100 μL of electrolyte was further added. A metallic lithium foil (3 cm × 3 cm) was left to face the negative electrode for precharging through a separator, 100 μL of electrolyte was added, the other copper foil in the laminate cell was covered, and heat-sealed first. Two sides orthogonal to one side were heat sealed. Thereafter, the laminate cell was sealed by heat-sealing the opening while evacuating the inside of the cell using a vacuum sealer to obtain a precharge battery.

[Precharge and production of negative electrode for lithium ion battery of the present invention]
Using a charge / discharge measuring device “HJ0501SM8A” [Hokuto Denko Co., Ltd.], CC-CV charging at 45 ° C., current 0.1 C, lower limit potential 0 V, 10 minutes rest, current 0.1 C, upper limit potential 1 Pre-charging was performed by CC discharge at .5V. Thereafter, the battery for precharging was disassembled and the negative electrode was taken out to obtain the negative electrode 1 for lithium ion battery of the present invention. The thickness of the negative electrode active material layer which the obtained negative electrode 1 for lithium ion batteries of this invention has was 350 micrometers.

<Example 2>
A battery for precharging was prepared in the same manner as in Example 1 except that the carbon-coated silicon particles were changed to SiO particles that were silicon oxide (manufactured by Sigma-Aldrich Japan, volume average particle diameter 5 μm) in the preparation of the negative electrode active material slurry. Then, preliminary charging was performed. Thereafter, the battery for precharging was disassembled and the negative electrode was taken out to obtain the negative electrode 2 for lithium ion battery of the present invention. The thickness of the negative electrode active material layer 2 included in the obtained negative electrode for a lithium ion battery of the present invention was 350 μm.

<Example 3>
In the preparation of the negative electrode active material slurry, the blending amount of the carbon-based coated negative electrode active material particles 1 was changed to 8.5 parts, and the carbon-coated silicon particles were changed to silicon particles [Sigma-Aldrich Japan, volume average particle diameter 5 μm]. Except for changing to 5 parts, a battery for preliminary charging was prepared in the same manner as in Example 1, and preliminary charging was performed. Thereafter, the battery for precharging was disassembled and the negative electrode was taken out to obtain the negative electrode 3 for lithium ion battery of the present invention. The thickness of the negative electrode active material layer 3 included in the obtained negative electrode for a lithium ion battery of the present invention was 380 μm.

<Example 4>
[Preparation of two types of negative electrode active material slurry]
After adding 10 parts of carbon-based coated negative electrode active material particles 2 (number average particle diameter 0.1 μm) obtained in Production Example 4 to 90 parts of the electrolytic solution, the mixture was mixed at 2000 rpm for 5 minutes using a planetary stirring type kneader. Thus, a negative electrode active material slurry 4-1 was produced. After adding 10 parts of silicon particles [volume average particle diameter 0.01 μm, manufactured by Sigma-Aldrich Japan Co., Ltd.] to 90 parts of the electrolytic solution, the mixture is mixed at 2000 rpm for 5 minutes using a planetary stirring type kneading apparatus, and the negative electrode active material A slurry 4-2 was produced.

[Preparation of negative electrode active material layer]
Prepare two sets of φ80mm aramid non-woven fabrics with overlapping masks with holes of φ70mm, and add negative electrode active material slurry 4-1 or negative electrode active material slurry 4-2 to each hole part of the mask. The solution was added dropwise so that the basis weight was 23.9 mg / cm ² . Further, each of the aramid nonwoven fabrics was subjected to suction filtration (reduced pressure) to produce a circular carbon-based coated negative electrode active material layer or silicon-based negative electrode active material layer having a diameter of 70 mm on each of the two aramid nonwoven fabrics. Next, the pre-charging carbon-based negative electrode 4-1 and the pre-charging silicon-based negative electrode 4-2 were prepared by pressing for about 10 seconds at a pressure of 25 MPa. Using the precharged carbon-based negative electrode 4-1 and the precharged silicon-based negative electrode 4-2, a precharge battery was prepared and precharged separately by the following method, and the lithium ion battery of the present invention was prepared. A carbon-based negative electrode active material doped with lithium ions and a silicon-based negative electrode active material doped with lithium ions were prepared.

[Preparation of battery for pre-charging]
Two copper foils (9 cm × 9 cm, thickness 17 μm) with terminals (5 mm × 3 cm) are stacked so that each terminal comes out in the same direction, and two sheets of commercially available heat-sealing aluminum laminate films (14 cm) × 13 cm), and one side where the terminal comes out was heat-sealed to prepare a pre-charging laminate cell. Two pre-charging laminate cells were prepared. The aramid non-woven fabric was peeled off from the pre-charging carbon-based negative electrode 4-1 and the pre-charging silicon-based negative electrode 4-2, and each was left standing on one copper foil in the pre-charging laminate cell, and 150 μL of electrolyte was added. . Next, a separator (12 cm × 11 cm, thickness 23 μm, Celgard 3501 PP) was allowed to stand on each negative electrode for precharging, and 100 μL of electrolyte was further added. A metallic lithium foil (7.5 cm × 7.5 cm) is left to face each negative electrode for precharging through a separator, 100 μL of electrolyte is added, and the other copper foil in the laminate cell is covered, The two sides orthogonal to the one side heat-sealed to were heat sealed. Then, the laminate cell was sealed by heat-sealing the opening while evacuating the inside of the cell using a vacuum sealer to obtain two types of precharge batteries.

[Precharge and production of negative electrode for lithium ion battery of the present invention]
Two types of preliminary charging batteries were precharged in the same manner as in Example 1. Thereafter, the battery for precharging is disassembled, the negative electrode is taken out, the active material is peeled off from the negative electrode and collected, and the carbon-based negative electrode active material 4-1 doped with lithium ions used for the negative electrode for the lithium ion battery of the present invention, lithium lithium A silicon-based negative electrode active material 4-2 doped with ions was obtained.

[Production of negative electrode]
3.8 parts of carbon-based negative electrode active material 4-1 doped with lithium ions, 3.2 parts of silicon-based negative electrode active material 4-2 doped with lithium ions, carbon fiber 3 obtained in Production Example 7 And 90 parts of electrolyte solution were added and mixed, and mixed for 5 minutes at 2000 rpm using a planetary stirring type mixing and kneading apparatus to prepare a negative electrode active material slurry 4-3. A mask having a hole of φ15 mm was placed on a φ23 mm aramid nonwoven fabric, and negative electrode active material slurry 4-3 was dropped into the hole of the mask so that the basis weight of the active material was 23.9 mg / cm ² . Further, a negative negative electrode active material layer having a diameter of 15 mm was produced by suction filtration (reduced pressure) from the aramid nonwoven fabric side. Subsequently, the negative electrode 4 for lithium ion batteries of this invention was obtained by pressing at a pressure of 5 MPa for about 10 seconds. The thickness of the negative electrode active material layer 4 included in the obtained negative electrode for a lithium ion battery of the present invention was 360 μm.

<Example 5>
In the production of the negative electrode of Example 4, the carbon-based negative electrode active material 4-1 doped with lithium ions was added to 3.5 parts, and the silicon-based negative electrode active material 4-2 doped with lithium ions was added to 3.5 parts. The negative electrode 5 for a lithium ion battery of the present invention was obtained in the same manner as in Example 4 except that the basis weight of the negative electrode active material when the electrode was produced after the change and doping was changed to 47.8 mg / cm ² . The thickness of the negative electrode active material layer 5 which the obtained negative electrode for lithium ion batteries of this invention has was 610 micrometers.

<Example 6>
In preparation of the negative electrode active material slurry of Example 1, the compounding quantity of the carbon-type covering negative electrode active material particle 1 was changed into 8.5 parts, and the silicon type negative electrode active material particle which produced the silicon type negative electrode active material in manufacture example 6 (Carbon-coated silicon oxide particles) Except for changing to 0.5 part, a battery for preliminary charging was prepared in the same manner as in Example 1, and preliminary charging was performed. Thereafter, the battery for precharging was disassembled and the negative electrode was taken out to obtain the negative electrode 6 for lithium ion battery of the present invention. The thickness of the negative electrode active material layer 6 included in the obtained negative electrode for a lithium ion battery of the present invention was 370 μm.

<Example 7>
In the production of the negative electrode active material slurry of Example 1, the compounding amount of the carbon-based coated negative electrode active material particles 1 was changed to 8.5 parts, and the carbon-coated silicon particles produced in Production Example 7 were 0.5 parts. A battery for preliminary charging was produced in the same manner as in Example 1 except that it was changed to, and preliminary charging was performed. Thereafter, the battery for precharging was disassembled and the negative electrode was taken out to obtain the negative electrode 7 for lithium ion battery of the present invention. The thickness of the negative electrode active material layer 7 included in the obtained negative electrode for a lithium ion battery of the present invention was 380 μm.

<Comparative Example 1>
In preparation of the negative electrode active material slurry, the carbon-based coated negative electrode active material particles 1 are uncoated non-graphitizable carbon powder [Carbotron (registered trademark) PS (F), manufactured by Kureha Battery Materials Japan, Inc., number The average particle diameter was changed to 6 parts], and Example 1 except that 50 parts of an N-methylpyrrolidone solution containing 5 parts of polyvinylidene fluoride (manufactured by Sigma-Aldrich) from which water was removed was added to the negative electrode active material slurry. Similarly, a negative electrode active material slurry used in Comparative Example 1 was produced. A mask having a hole of φ15 mm was overlapped on a φ23 mm aramid nonwoven fabric, and a negative electrode active material slurry was dropped into the hole portion of the mask so as to have a basis weight of 23.9 mg / cm ² . Further, a negative negative electrode active material layer having a diameter of 15 mm was produced by suction filtration (reduced pressure) from the aramid nonwoven fabric side. Next, after pressing at 5 MPa for 10 seconds, the aramid nonwoven fabric was peeled off, and then dried at 100 ° C. for 15 minutes to prepare a negative electrode for precharging. The solid content concentration in the negative electrode active material layer of the negative electrode for precharging was 99% by mass or more. Next, preliminary charging was performed in the same manner as in Example 1 to obtain a comparative lithium ion battery negative electrode (thickness: 300 μm).

<Evaluation of negative electrode for lithium ion battery>
A battery for evaluation was produced by the following method, and a negative electrode for a lithium ion battery was evaluated.

[Production of lithium-ion batteries]
A copper foil (3 cm × 3 cm, thickness 17 μm) with a terminal (5 mm × 3 cm) is stacked so that each terminal comes out in the same direction, and two commercially available heat-sealing aluminum laminate films (10 cm × 8 cm) ) And heat-bonded one side of the terminal to produce a laminate cell for evaluation. The negative electrode for a lithium ion battery obtained in each example or comparative example was placed on one copper foil of the laminate cell for evaluation. After adding 30 μL of the electrolytic solution to the negative electrode, the separator was placed on the negative electrode, and 100 μL of the electrolytic solution was further added. A Li metal (Φ15, thickness 0.5 mm) made by Honjo Metal was placed so as to face the negative electrode with a separator interposed therebetween, and 100 μL of an electrolytic solution was added. The other copper foil in the laminate cell for evaluation was placed thereon, and two sides orthogonal to one side heat-sealed previously were heat sealed. Thereafter, the laminate cell was sealed by heat-sealing the opening while evacuating the inside of the cell using a vacuum sealer to obtain a lithium ion battery for evaluation.

[Evaluation of charge / discharge cycle characteristics of lithium-ion batteries]
Using a charge / discharge measuring device “HJ0501SM8A” (Hokuto Denko Co., Ltd.), CC-CV charging at 45 ° C., current 0.1 C, upper limit potential 0 V, and after 10 minutes of rest, current 0.1 C, lower limit potential 1 The operation of performing CC discharge at .5V was performed 10 cycles, and the capacity retention rate as the cycle characteristics was calculated by the following formula using the discharge capacity of the first cycle and the discharge capacity of the 10th cycle. In addition, it means that it has the cycling characteristics which there are few falls of a capacity | capacitance, so that the value of a capacity | capacitance maintenance factor is large.
[Capacity maintenance ratio (%)] = [Discharge capacity at 10th cycle] ÷ [Discharge capacity at 1st cycle] × 100].

[Measurement of change in electrode thickness after initial charge]
The amount of change in the thickness of the negative electrode active material after the first charge is obtained by subtracting the thickness of the negative electrode active material before the first charge from the thickness of the negative electrode active material after the first charge. The thickness of the negative electrode active material layer was measured using a contact-type film thickness meter [ABS Digimatic Indicator ID-CX manufactured by Mitutoyo Corporation].

Table 1 summarizes the preliminary charging methods of each example and comparative example, the configuration of the negative electrode active material layer, and the evaluation results. In Table 1, the preliminary charging method 1 is a method of simultaneously performing a step of doping lithium ions into a silicon-based negative electrode active material and a step of doping lithium ions into a carbon-based negative electrode active material. It means a method in which the step of doping lithium ion into the negative electrode active material and the step of doping lithium ion into the carbon negative electrode active material are performed separately.

As shown in Table 1, when the negative electrodes for lithium ion batteries produced in Examples 1 to 7 were used, the capacity retention rate could be increased. In Examples 1 to 7, the volume change (the amount of change in thickness after the first charge) was also small.

This application is based on Japanese Patent Application No. 2016-246998 filed on December 20, 2016 and Japanese Patent Application No. 2017-238949 filed on December 13, 2017, the disclosure of which is incorporated herein by reference. The contents are cited as a whole by reference.

The negative electrode for lithium ion batteries of the present invention is particularly useful as a negative electrode for bipolar secondary batteries and lithium ion batteries used for mobile phones, personal computers, hybrid vehicles, and electric vehicles.

Claims

A negative electrode for a lithium ion battery having a step of forming a coating film on a current collector or a separator using a slurry containing a negative electrode active material composition containing a silicon-based negative electrode active material and a carbon-based negative electrode active material, and a dispersion medium A manufacturing method comprising:
Before or after the step of forming the coating film and before assembling the lithium ion battery, a step of doping lithium ions into the silicon-based negative electrode active material, and a step of doping lithium ions into the carbon-based negative electrode active material Including
The manufacturing method of the negative electrode for lithium ion batteries which does not include the process of drying the said coating film substantially.
2. The method for producing a negative electrode for a lithium ion battery according to claim 1, wherein the slurry does not substantially contain a binder.
Doping the lithium-based negative electrode active material with lithium ions;
The method for producing a negative electrode for a lithium ion battery according to claim 1, wherein the step of doping the carbon-based negative electrode active material with lithium ions is performed simultaneously.
Doping the lithium-based negative electrode active material with lithium ions;
The carbon-based negative electrode active material is separately doped with lithium ions,
The method for producing a negative electrode for a lithium ion battery according to claim 1 or 2, further comprising a step of mixing a silicon-based negative electrode active material doped with lithium ions and a carbon-based negative electrode active material doped with lithium ions.
The step of doping lithium ions into the carbon-based negative electrode active material is a step of doping lithium ions into the carbon-based negative electrode active material contained in a mixture of the carbon-based negative electrode active material and a silicon-based negative electrode active material doped with lithium ions. The manufacturing method of the negative electrode for lithium ion batteries of any one of Claims 1, 2, and 4 which is these.
The step of doping lithium ions into the silicon-based negative electrode active material is a step of doping lithium ions into the silicon-based negative electrode active material contained in the mixture of the silicon-based negative electrode active material and the carbon-based negative electrode active material doped with lithium ions. The manufacturing method of the negative electrode for lithium ion batteries of any one of Claims 1, 2, and 4 which is these.
The silicon-based negative electrode active material and the carbon-based negative electrode active material contained in the slurry are a silicon-based negative electrode active material and a carbon-based negative electrode active material before being doped with lithium ions, according to any one of claims 1 to 6. The manufacturing method of the negative electrode for lithium ion batteries of description.
The silicon-based negative electrode active material and the carbon-based negative electrode active material contained in the slurry are a silicon-based negative electrode active material and a carbon-based negative electrode active material after being doped with lithium ions, according to any one of claims 1 to 6. The manufacturing method of the negative electrode for lithium ion batteries of description.
A negative electrode active material composition obtained by the production method according to any one of claims 1 to 8 and comprising a carbon-based negative electrode active material doped with lithium ions and a silicon-based negative electrode active material doped with lithium ions A negative electrode for a lithium ion battery, comprising a negative electrode active material layer made of a non-binding product of the product.
The negative electrode for a lithium ion battery according to claim 9, wherein a part or all of the surface of the carbon-based negative electrode active material is coated with a negative electrode coating layer comprising a polymer compound that is a coating resin.
The negative electrode for a lithium ion battery according to claim 9 or 10, wherein the silicon-based negative electrode active material is silicon and / or a silicon compound.
The silicon compound includes silicon oxide (SiOx), Si—C composite, Si—Al alloy, Si—Li alloy, Si—Ni alloy, Si—Fe alloy, Si—Ti alloy, Si—Mn alloy, Si—Cu. The negative electrode for a lithium ion battery according to claim 11, wherein the negative electrode is at least one selected from the group consisting of an alloy and a Si-Sn alloy.