JP2019160690A - Electrode binder, electrode mixture, energy device electrode and energy device - Google Patents

Abstract

To provide a binder that can produce electrodes for energy devices with excellent cycle characteristics.SOLUTION: The electrode binder has a structural unit containing a nitrile group and a structural unit containing an acidic functional group. At least one part of the acidic functional group contains a copolymer which forms a salt and a base.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electrode binder, an electrode mixture, an energy device electrode, and an energy device.

  2. Description of the Related Art Lithium ion secondary batteries, which are non-aqueous electrolyte energy devices having a high energy density, are widely used as power sources for portable information terminals such as notebook personal computers, mobile phones, and PDAs, and power sources for electric vehicles.

  The electrode of the lithium ion secondary battery is produced as follows. First, an active material, a binder and a solvent are kneaded to prepare a slurry electrode mixture. This electrode mixture is applied to one or both sides of a metal foil as a current collector with a transfer roll or the like, and the solvent is removed by drying to form a mixture layer. Then, an electrode is produced through the process of compression-molding a mixture layer with a roll press machine.

  The binder used here is required to have excellent properties such as adhesion between the active materials and between the active material and the current collector, and electrochemical stability. Further, it is required to satisfy these characteristics with a smaller addition amount in order to increase the capacity of the lithium ion secondary battery. Furthermore, it is considered preferable to use water as the solvent used for preparing the electrode mixture from the viewpoint of reducing the environmental load, and compatibility with aqueous solvents is one of the requirements for the binder.

  As a binder used together with an aqueous solvent, Patent Document 1 discloses an aqueous dispersion of a copolymer containing a structural unit derived from (meth) acrylonitrile and a structural unit derived from a compound having two or more ethylenically unsaturated bonds. Has been. Patent Document 2 discloses an aqueous dispersion of a copolymer having a structural unit derived from (meth) acrylonitrile and a structural unit derived from (meth) acrylic ester and having a swelling degree of 200 to 400% with respect to the electrolytic solution. It is disclosed.

International Publication No. 2014/098233 Japanese Patent Laid-Open No. 2006-143635

  In recent years, the use of silicon oxide as a negative electrode active material has been studied against the background of increasing the capacity of lithium ion secondary batteries. When silicon oxide is used as the negative electrode active material, a significant improvement in the discharge capacity of the lithium ion secondary battery can be expected.

  However, on the other hand, the active material made of silicon oxide has a large volume expansion / contraction due to charge / discharge, so that sufficient adhesion between the active materials or between the active material and the current collector cannot be obtained. May occur. In addition, a protective film (Solid Electrolyte Interface, SEI) formed on the surface of the active material at the time of charge / discharge may be cracked, peeled off, etc. to form an active surface, and decomposition of the electrolyte may proceed. For this reason, the lithium ion secondary battery using silicon oxide as an active material has a problem that the cycle characteristics relating to the life are not sufficient.

  As a measure to solve the above problems, sufficient adhesion between active materials or between an active material and a current collector is ensured even if volume expansion and contraction occurs due to charge and discharge, and cracking of SEI is sufficiently suppressed. It is conceivable to use a binder that can be used. However, with the binders described in Patent Document 1 and Patent Document 2, sufficient cycle characteristics cannot be improved.

  This invention makes it a subject to provide the binder which can manufacture the electrode of the energy device which is excellent in cycling characteristics in view of the said situation. Another object of the present invention is to provide an electrode mixture, an energy device electrode and an energy device using the binder.

Means for solving the above problems include the following embodiments.
<1> For electrodes comprising a nitrile group-containing structural unit and an acidic functional group-containing structural unit, wherein at least a part of the acidic functional group forms a salt with a base. binder.
<2> The ratio (A: B) of the structural unit A containing the nitrile group to the structural unit B containing the acidic functional group in the copolymer is 1: 0.1 to 1: 1. The binder for electrodes as described in <1> which exists in the range of 0.5.
<3> The total ratio of the structural unit containing the nitrile group and the structural unit containing the acidic functional group in the copolymer is 95 mol% or more of all the structural units constituting the copolymer. The electrode binder according to <1> or <2>.
<4> The copolymer does not contain a hydrocarbon group in the side chain, or when it contains a hydrocarbon group in the side chain, the number of carbon atoms is 5 or less, and any one of <1> to <3> The binder for electrodes as described in claim | item.
<5> The electrode binder according to any one of <1> to <4>, wherein the copolymer has a weight average molecular weight of 50,000 to 200,000.
<6> The binder for electrodes according to any one of <1> to <5>, further including water, wherein the copolymer is dissolved in the water.
<7> The electrode binder according to any one of <1> to <6>, wherein the acidic functional group includes at least one selected from the group consisting of a carboxy group, a sulfo group, and a phospho group.
<8> The structural unit having the acidic functional group is derived from at least one selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, crotonic acid, itaconic acid, citraconic acid, vinylbenzoic acid and vinylbenzenesulfonic acid. <1>-<7> The binder for electrodes as described in any one of <7>.
<9> The electrode binder according to any one of <1> to <8>, wherein the structural unit containing the nitrile group is derived from acrylonitrile.
<10> The binder for an electrode according to any one of <1> to <9>, for forming an electrode containing a compound containing silicon as an active material.
<11> Electrode mixture containing the binder for electrodes as described in any one of <1>-<10>, and an active material.
<12> The electrode mixture according to <11>, wherein the active material contains a compound containing silicon.
<13> An electrode for an energy device, comprising: a current collector; and an electrode mixture layer provided on at least one surface of the current collector and including the electrode mixture according to <11> or <12>. .
<14> An energy device comprising a positive electrode and a negative electrode, wherein at least one of the positive electrode and the negative electrode comprises the electrode binder and the active material according to any one of <1> to <10>.

  ADVANTAGE OF THE INVENTION According to this invention, the binder which can manufacture the electrode of the energy device excellent in cycling characteristics is provided. Moreover, according to this invention, the electrode mixture using this binder, the electrode for energy devices, and an energy device are provided.

It is sectional drawing which shows an example of a structure of the lithium ion secondary battery which is an example of an energy device.

Hereinafter, embodiments for carrying out the present invention will be described in detail. However, the present invention is not limited to the following embodiments. In the following embodiments, the components (including element steps and the like) are not essential unless otherwise specified. The same applies to numerical values and ranges thereof, and the present invention is not limited thereto.
In this specification, the term “process” includes a process that is independent of other processes and includes the process if the purpose of the process is achieved even if it cannot be clearly distinguished from the other processes. It is.
In the present specification, the numerical ranges indicated by using “to” include numerical values described before and after “to” as the minimum value and the maximum value, respectively.
In the numerical ranges described stepwise in this specification, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of another numerical range. Good. Further, in the numerical ranges described in this specification, the upper limit value or the lower limit value of the numerical range may be replaced with the values shown in the examples.
In the present specification, the content of each component in the composition is the sum of the plurality of substances present in the composition unless there is a specific indication when there are a plurality of substances corresponding to each component in the composition. It means the content rate of.
In the present specification, the particle diameter of each component in the composition is a mixture of the plurality of types of particles present in the composition unless there is a specific indication when there are a plurality of types of particles corresponding to each component in the composition. Means the value of.
In this specification, the term “layer” or “film” refers to a part of the region in addition to the case where the layer or the film is formed when the region where the layer or film exists is observed. It is also included when it is formed only.
In this specification, the term “lamination” indicates that layers are stacked, and two or more layers may be combined, or two or more layers may be detachable.
In the present specification, “(meth) acryl” means at least one of acryl and methacryl, “(meth) acrylate” means at least one of acrylate and methacrylate, and “(meth) allyl” means at least one of allyl and methallyl. Mean one.

<Binder for electrode>
An electrode binder of the present disclosure (hereinafter also simply referred to as a binder) has a structural unit containing a nitrile group and a structural unit containing an acidic functional group, and at least a part of the acidic functional group is a base and a salt. A copolymer (hereinafter, also simply referred to as a copolymer).

  The copolymer contained in the binder of the present disclosure is excellent in solubility in water because at least a part of the acidic functional group forms a salt by a neutralization reaction with a base. As a result of the study by the present inventors, it was found that when the binder containing the copolymer is used as a binder for an electrode of an energy device, the cycle characteristics of the energy device are improved.

  The reason why the cycle characteristics of the energy device are improved by using the binder of the present disclosure is not necessarily clear, but, for example, a water-insoluble binder is mixed with an active material in a state of being dispersed in water, and in a state of fine particles in an electrode While the active materials are bonded to each other between the active materials, it is considered that the binder of the present disclosure is water-soluble, so that it is easy to make a state of covering the surface of the active material. As a result, phenomena such as desorption and destruction from the electrode and separation of SEI formed on the surface due to the expansion and contraction of the active material are suppressed by the binder that covers the surface of the active material, and the deterioration of the electrode is difficult to proceed. Thus, the cycle characteristics are considered to be improved.

  The binder of the present disclosure is particularly suitable as a binder for an electrode containing an active material having a large degree of expansion and contraction because it has an excellent effect of suppressing deterioration of the electrode due to expansion and contraction of the active material. Examples of the active material having a large degree of expansion and contraction include compounds containing silicon.

  Furthermore, since the binder of the present disclosure can be used in the state of an aqueous solution in which a copolymer is dissolved in water, an electrode can be produced without using an organic solvent to dissolve the copolymer, and safety and environment can be improved. Excellent in compatibility. Moreover, since the binder of this indication has a high viscosity compared with the state in which the copolymer was disperse | distributed to water, addition of thickeners, such as carboxymethylcellulose, can also be abbreviate | omitted. For this reason, the fall of the adhesiveness resulting from a thickener, a storage stability, etc. can be avoided.

(Copolymer)
The copolymer is particularly limited as long as it has a structural unit containing a nitrile group and a structural unit containing an acidic functional group, and at least a part of the acidic functional group forms a salt with a base. Not. For example, a monomer containing a nitrile group (hereinafter also referred to as a nitrile group-containing monomer), a monomer containing an acidic functional group (hereinafter also referred to as an acidic functional group-containing monomer), and a necessity Accordingly, a copolymer obtained by a polymerization reaction with another monomer may be obtained by reacting a basic compound.

  When the structural unit of the copolymer has a nitrile group, excellent binder toughness and excellent resistance to an electrolyte solution tend to be obtained. Further, since the structural unit of the copolymer has an acidic functional group, excellent solubility in water and excellent adhesion to an active material tend to be obtained.

  The ratio of the structural unit containing a nitrile group and the structural unit containing an acidic functional group in the copolymer is not particularly limited. From the viewpoint of the balance of properties as a binder, for example, the ratio (A: B) of the structural unit A containing a nitrile group to the structural unit B containing an acidic functional group is 1: 0.1 to 1 in terms of molar ratio. : It may be in the range of 1.5.

  Some of the acidic functional groups in the copolymer may form a salt with the base, or all of them may form a salt. For example, 50 mol% or more of the acidic functional groups in the copolymer may form a salt, 80 mol% or more may form a salt, and 90 mol% or more form a salt. Also good. The proportion of the acidic functional group that forms a salt can be adjusted by the amount of the basic compound to be reacted with the copolymer.

  The total ratio of the structural unit containing a nitrile group and the structural unit containing an acidic functional group in the copolymer is not particularly limited. For example, the total ratio of the structural unit containing a nitrile group and the structural unit containing an acidic functional group in the copolymer may be 95 mol% or more of all the structural units constituting the copolymer. 99 mol% or more, or more than 99 mol%.

  From the viewpoint of suppressing excessive swelling into the electrolytic solution, the copolymer does not contain a hydrocarbon group in the side chain, or if it contains a hydrocarbon group in the side chain, the number of carbon atoms may be 5 or less. Preferably, when the hydrocarbon group is not included in the side chain, or when the hydrocarbon group is included in the side chain, the number of carbon atoms is more preferably 3 or less, the hydrocarbon group is not included in the side chain, or the hydrocarbon When the group is included in the side chain, the number of carbon atoms is more preferably 2 or less, and it is particularly preferable that the hydrocarbon group is not included in the side chain. The hydrocarbon group here includes a combination of a hydrocarbon group and an oxygen atom (an alkyleneoxy group or the like).

  The weight average molecular weight of the copolymer is preferably 50,000 to 200,000, and more preferably 70,000 to 150,000. When the weight average molecular weight of the copolymer is 50,000 or more, the coating formed on the surface of the active material tends to have excellent stability, and when it is 200,000 or less, the coating of the active material tends to be excellent. The weight average molecular weight of the copolymer can be adjusted by the temperature during the polymerization reaction (the molecular weight tends to decrease as the temperature increases), the type of polymerization initiator, the addition of a chain transfer agent, and the like.

In the present disclosure, the weight average molecular weight of the copolymer is a value measured as follows.
A measurement object is dissolved in N-methyl-2-pyrrolidone, and a PTFE (polytetrafluoroethylene) filter (Kurashiki Boseki Co., Ltd., HPLC (high performance liquid chromatography) pretreatment, chromatodisc, model number: 13N, pore size: 0 .45 μm] to remove insoluble matter. GPC [Pump: L6200 Pump (Hitachi, Ltd.), Detector: Differential refractive index detector L3300 RI Monitor (Hitachi, Ltd.), Column: TSKgel-G5000HXL and TSKgel-G2000HXL (both in total) (both Tosoh Corporation) ) In series, column temperature: 30 ° C., eluent: N-methyl-2-pyrrolidone, flow rate: 1.0 mL / min, standard substance: polystyrene], and the weight average molecular weight is measured.

  The acid value of the copolymer is preferably 0 mgKOH / g to 70 mgKOH / g, more preferably 0 mgKOH / g to 20 mgKOH / g, and still more preferably 0 mgKOH / g to 5 mgKOH / g.

In the present disclosure, the acid value of the copolymer is a value measured as follows.
First, after precisely weighing 1 g of a measurement object, 30 g of acetone is added to the measurement object, and the measurement object is dissolved. Next, an appropriate amount of an indicator, phenolphthalein, is added to the solution to be measured and titrated with a 0.1N aqueous KOH solution. Then, the acid value is calculated from the titration result by the following formula (A) (where Vf represents the titration amount (mL) of phenolphthalein, Wp represents the mass (g) of the solution to be measured, and I represents (The ratio (% by mass) of the nonvolatile content of the solution to be measured is shown.)
Acid value (mgKOH / g) = 10 × Vf × 56.1 / (Wp × I) (A)
The nonvolatile content of the solution to be measured is calculated from the weight of the residue by weighing about 1 mL of the solution to be measured in an aluminum pan, drying it on a hot plate heated to 160 ° C. for 15 minutes.

-Nitrile group-containing monomer-
When the copolymer is prepared using a nitrile group-containing monomer, the type of the nitrile group-containing monomer used is not particularly limited. In general, a compound having an ethylenically unsaturated double bond and a nitrile group, which can introduce a nitrile group into the side chain of the copolymer, can be mentioned. Examples include acrylic nitrile group-containing monomers such as acrylonitrile and methacrylonitrile, cyan nitrile group-containing monomers such as α-cyanoacrylate and dicyanovinylidene, and fumaric nitrile group-containing monomers such as fumaronitrile. It is done. Furthermore, a monomer (for example, containing a hydrocarbon group (may be a combination with an oxygen atom) having 5 or less carbon atoms, preferably 3 or less carbon atoms, more preferably 2 or less carbon atoms, and a nitrile group (for example, Monomers represented by the following general formulas (I) to (IV)). A nitrile group containing monomer may be used individually by 1 type, and may be used in combination of 2 or more type.

In the formula, R ₉ is H or CH ₃ . R ₁₀ is an alkylene group having 1 to 3 carbon atoms, preferably a methylene group.

In the formula, R ₁₁ is H or CH ₃ . n is 0 or 1, preferably 0.

In the formula, R ₁₂ is H or CH ₃ . R ₁₃ is an alkylene group having 1 to 3 carbon atoms, preferably a methylene group.

In the formula, R ₁₄ is H or CH ₃ . R ₁₅ is a single bond, an alkylene group having 1 to 3 carbon atoms or an alkyleneoxy group, preferably a single bond or a methylene group.

  Among these, acrylonitrile or methacrylonitrile is preferable, and acrylonitrile is more preferable in terms of ease of polymerization, cost performance, electrode flexibility, flexibility, and the like.

-Acid functional group-containing monomer-
When the copolymer is prepared using an acidic functional group-containing monomer, the acidic functional group-containing monomer is not particularly limited. In general, a compound having an ethylenically unsaturated double bond and an acidic functional group, which can introduce an acidic functional group into the side chain of the copolymer. Examples of the acidic functional group include a carboxy group, a sulfo group, and a phospho group, and among them, a carboxy group is preferable.

  Monomers containing a carboxy group as an acidic functional group include acrylic carboxy group-containing monomers such as acrylic acid and methacrylic acid, croton carboxy group-containing monomers such as crotonic acid, maleic acid, and anhydrides thereof. Maleic carboxy group-containing monomers such as itaconic acid and its anhydride, etc. carboxy group-containing monomers such as citraconic acid and its anhydride, citraconic carboxy group-containing monomers such as vinyl benzoic acid, etc. Can be mentioned. Further, a monomer containing a hydrocarbon group (which may be a combination with an oxygen atom) having 5 or less carbon atoms, preferably 3 or less carbon atoms, more preferably 2 or less carbon atoms, and a carboxy group (for example, Monomers represented by the following general formulas (V) and (VI)).

In the formula, R ₅ is H or CH ₃ . R ₆ is an alkylene group having 1 to 5 carbon atoms or an alkyleneoxy group, preferably an alkylene group having 1 or 2 carbon atoms or an alkyleneoxy group, and more preferably a methylene group.

Here, R ₇ is H or CH ₃ . R ₈ is an alkylene chain or alkyleneoxy chain having 1 to 5 carbon atoms, preferably an alkylene group or alkyleneoxy group having 1 or 2 carbon atoms, and more preferably a methylene group.

  Monomers containing a sulfo group as an acidic functional group include vinylbenzene sulfonic acid, (meth) allyl sulfonic acid, (meth) allyloxybenzene sulfonic acid, styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid And salts thereof (sodium salt, lithium salt, etc.).

  Examples of the monomer containing a phospho group as an acidic functional group include acid phosphooxyethyl methacrylate (Unichemical Co., Ltd., trade name: Phosmer M), acid phosphoxypolyoxyethylene glycol monomethacrylate (Unichemical Co., Ltd., trade name) : Phosmer PE), 3-chloro-2-acid phosphooxypropyl methacrylate (Unichemical Corporation, trade name: Phosmer CL), Acid phosphoxypolyoxypropylene glycol monomethacrylate (Unichemical Corporation, trade name: Phosmer PP) Etc.

  Among these, a monomer containing a carboxy group as an acidic functional group is preferable, acrylic acid or methacrylic acid is more preferable, and acrylic acid is more preferable.

-Other monomers-
When the copolymer is prepared using a monomer other than the nitrile group-containing monomer or the acidic functional group-containing monomer (hereinafter also referred to as other monomer), the type is not particularly limited.
Other monomers include (meth) acrylic acid esters containing alkyl groups such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, vinyl chloride, vinyl bromide, vinylidene chloride, etc. Examples thereof include vinyl halides, maleic imide, phenylmaleimide, (meth) acrylamide, styrene, α-methylstyrene, and vinyl acetate. Other monomers may be used alone or in combination of two or more.

-Basic compounds-
The acidic functional group forming a salt in the copolymer may be obtained, for example, by reacting the acidic functional group of the copolymer with a basic compound.

  The kind of basic compound is not particularly limited. For example, a basic compound derived from metal or a basic compound not derived from metal may be used. Specific examples of metal-derived basic compounds include lithium hydroxide, sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide, barium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, magnesium carbonate, calcium carbonate. Inorganic basic substances such as barium carbonate, lithium hydrogen carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, magnesium hydrogen carbonate, calcium hydrogen carbonate, barium hydrogen carbonate, lithium methoxide, sodium methoxide, lithium tert-butoxide, potassium tert- Examples thereof include metal alcoholates such as butoxide. Examples of basic compounds not derived from metals include ammonia, amine compounds, pyridine compounds, and azole compounds. A basic compound may be used individually by 1 type, and may be used in combination of 2 or more type.

  As an amine compound, a C1-C50 thing is preferable and a C3-C25 thing is more preferable. Tertiary amine compounds are preferred. Specific examples of the amine compound include the following compounds. Ph represents a phenyl group.

As a pyridine compound, a C5-C20 thing is preferable and a C5-C10 thing is more preferable. Examples thereof include pyridine derivatives such as pyridine and picoline.
As an azole compound, a C2-C20 thing is preferable and a C2-C10 thing is more preferable. For example, triazole and its derivative are mentioned.
Specific examples of the pyridine compound and the azole compound include the following compounds.

-Copolymer synthesis method-
The method for synthesizing the copolymer is not particularly limited. Polymerization methods such as precipitation polymerization in water, bulk polymerization, suspension polymerization, emulsion polymerization, and solution polymerization can be applied. In terms of ease of resin synthesis, ease of post-processing such as recovery and purification, precipitation polymerization in water and emulsion polymerization are preferred, and precipitation polymerization in water is more preferred.

As the polymerization initiator used when synthesizing the copolymer, it is preferable to use a water-soluble polymerization initiator in view of polymerization initiation efficiency.
Examples of the water-soluble polymerization initiator include persulfates such as ammonium persulfate, potassium persulfate, and sodium persulfate, water-soluble peroxides such as hydrogen peroxide, 2,2′-azobis (2-methylpropionamidine hydrochloride). ) And other water-soluble azo compounds, persulfates and other oxidizing agents, sodium bisulfite, ammonium bisulfite, sodium thiosulfate, hydrosulfite and other reducing agents, and polymerization accelerators such as sulfuric acid, iron sulfate and copper sulfate. Examples thereof include a combined oxidation-reduction type (redox type) polymerization initiator.
Of these, persulfates (more preferably ammonium persulfate) and water-soluble azo compounds are preferred in terms of ease of resin synthesis and the like.
The polymerization initiator is preferably used, for example, in the range of 0.001 mol% to 5 mol%, and 0.01 mol% to 2 mol, based on the total amount of monomers used for the synthesis of the copolymer. More preferably, it is used in the range of mol%.

  When synthesizing the copolymer, a chain transfer agent may be used for the purpose of adjusting the molecular weight. Examples of the chain transfer agent include mercaptan compounds such as thioglycol, carbon tetrachloride, α-methylstyrene dimer, and the like. Among these, α-methylstyrene dimer is preferable from the viewpoint of low odor.

When synthesizing the copolymer, a solvent may be used. Examples of the solvent include water and an organic solvent. When the copolymer is synthesized by precipitation polymerization in water, water and an organic solvent may be used in combination for adjusting the particle size of the copolymer to be precipitated.
Examples of solvents other than water include amides such as N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, N, N-dimethylethyleneurea, N, N-dimethylpropyleneurea, tetra Ureas such as methylurea, lactones such as γ-butyrolactone and γ-caprolactone, carbonates such as propylene carbonate, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methyl acetate, ethyl acetate, n-butyl acetate , Esters such as butyl cellosolve acetate, butyl carbitol acetate, ethyl cellosolve acetate and ethyl carbitol acetate, glymes such as diglyme, triglyme and tetraglyme, carbonized such as toluene, xylene and cyclohexane Examples thereof include hydrogens, sulfoxides such as dimethyl sulfoxide, sulfones such as sulfolane, alcohols such as methanol, isopropanol, and n-butanol. These solvent may be used individually by 1 type, and may be used in combination of 2 or more type.

The synthesis conditions for the copolymer are not particularly limited. For example, the monomer is introduced into a solvent, and the polymerization temperature is preferably 0 ° C. to 100 ° C., more preferably 30 ° C. to 90 ° C., preferably 1 hour to 50 hours, more preferably 2 hours to 12 hours. Is done by doing.
If the polymerization temperature is 0 ° C. or higher, the polymerization reaction tends to be promoted. Further, when the polymerization temperature is 100 ° C. or lower, even when water is used as a solvent, the water tends to evaporate and it becomes difficult to perform polymerization.

  By reacting the acidic functional group of the synthesized copolymer with a basic compound, at least a part of the acidic functional group can be in a state in which a salt is formed.

  The method for reacting the copolymer with the basic compound is not particularly limited, and can be carried out by a known method. The amount of the basic compound used for the reaction with the copolymer can be set according to the amount of the acidic functional group contained in the copolymer, the ratio of the acidic functional group to be reacted with the base, and the like.

  The amount of the basic compound is, for example, preferably 0.01 molar equivalent to 1.5 molar equivalent with respect to the acidic functional group contained in the copolymer, and 0.3 molar equivalent to 1.1 molar equivalent. More preferably, it is more preferably 0.5 molar equivalent to 1.0 molar equivalent.

-Use of binder-
The binder of the present disclosure is suitably used as a material for an electrode of an energy device, particularly a non-aqueous electrolyte type energy device. A non-aqueous electrolyte-based energy device refers to a power storage or power generation device (apparatus) that uses an electrolyte other than water. Examples of the energy device include a lithium ion secondary battery, an electric double layer capacitor, a solar cell, and a fuel cell. Especially, it utilizes suitably as a material of the electrode which contains the compound containing silicon with a large expansion-contraction by charging / discharging as an active material.

<Electrode mixture>
The electrode mixture of the present disclosure includes the binder described above and an active material. The type of active material contained in the electrode mixture is not particularly limited, and can be selected from those generally used as an electrode material for energy devices. Since the binder contained in the electrode mixture of the present disclosure is excellent in the coverage of the active material, an electrode having excellent cycle characteristics can be formed even when the active material contains a large expansion / contraction due to charge / discharge. it can.

  The active material contained in the electrode mixture may include a compound containing silicon. When a silicon-containing compound is used as an active material for a negative electrode of an energy device (negative electrode active material), the capacity can be increased compared to a negative electrode active material such as graphite, but the expansion and contraction accompanying charge / discharge is large. The active material tends to deteriorate and the cycle characteristics are difficult to maintain.

  Examples of the compound containing silicon include silicon oxide, and examples of the silicon oxide include silicon monoxide, silicon dioxide, and silicon suboxide. These may be used individually by 1 type and may be used in combination of 2 or more type.

  Silicon monoxide can be obtained, for example, by a known sublimation method in which a gas of silicon monoxide generated by heating a mixture of silicon dioxide and metal silicon is cooled and precipitated. Moreover, it can obtain from a market as a silicon oxide, silicon monoxide, etc.

  The silicon oxide may have a structure in which silicon crystallites are dispersed in silicon oxide (preferably a structure in which silicon crystallites are dispersed in silicon dioxide). If silicon crystallites are present in the silicon oxide, it is easy to obtain a high initial discharge capacity and good initial charge / discharge efficiency.

  When the silicon oxide is in the form of particles, the average particle diameter is not particularly limited. For example, the thickness is preferably 0.1 μm to 20 μm, and more preferably 0.5 μm to 10 μm.

In the present disclosure, the average particle diameter of the active material is a volume standard measured by using a laser diffraction particle size distribution measuring apparatus (for example, Shimadzu Corporation, SALD-3000J) by dispersing a sample in purified water containing a surfactant. In the particle size distribution, the value when the integration from the small diameter side becomes 50% (median diameter (D50)) is used.
A BET specific surface area can be measured from nitrogen adsorption capacity according to JIS Z 8830: 2013, for example. For example, QUANTACHROME: AUTOSORB-1 (trade name) can be used as the evaluation device. Since water adsorbed on the sample surface and in the structure is considered to affect the gas adsorption capacity, it is preferable to first perform pretreatment for removing water by heating when measuring the BET specific surface area.
In the pretreatment, a measurement cell charged with 0.05 g of a measurement sample is depressurized to 10 Pa or less with a vacuum pump, heated at 110 ° C. and held for 3 hours or more, and then kept at a normal temperature ( Cool to 25 ° C). After performing this pretreatment, the evaluation temperature is 77K, and the evaluation pressure range is measured as a relative pressure (equilibrium pressure with respect to saturated vapor pressure) of less than 1.

  The silicon oxide particles can be produced, for example, by pulverizing and classifying bulk silicon oxide. Specifically, it is preferable to firstly perform primary pulverization and classification in which the bulk silicon oxide is pulverized to a size that can be charged into a fine pulverizer, and then secondary pulverize (classify) the pulverized product with a fine pulverizer.

  The electrode mixture of the present disclosure may include a compound containing silicon as an active material and another active material. The other active material may be selected from those commonly used as a negative electrode active material of a lithium ion secondary battery, for example. Specific examples include carbon materials, metallic lithium, lithium alloys, intermetallic compounds, metal complexes, and organic polymer compounds. Among these, a carbon material is preferable. Examples of the carbon material include graphite such as natural graphite (such as flake graphite) and artificial graphite, carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black, and carbon fiber.

Among the carbon materials, from the viewpoint of improving the characteristics of the energy device, the distance (d ₀₀₂ ) between the carbon hexagonal planes in the X-ray wide angle diffraction method is 3.35 to 3.40 mm, and the crystallite (Lc) in the c-axis direction Is preferably a carbon material (graphite) having a thickness of 100% or more.
On the other hand, from the viewpoint of improving the cycle characteristics and safety of the energy device, a carbon material (amorphous carbon) in which the spacing (d ₀₀₂ ) of the carbon hexagonal plane in the X-ray wide angle diffraction method is 3.50 to 3.95 mm Is preferred.
The average particle size of the carbon material is preferably 0.1 μm to 60 μm, and more preferably 0.5 μm to 30 μm. Further, BET specific surface area of the carbon material ^is preferably 1m ² / g~10m 2 / g.

  The electrode mixture of the present disclosure is suitable as an electrode mixture for a negative electrode in which a production method using an aqueous solvent is adopted because the binder contained therein is excellent in compatibility with an aqueous solvent. It may be an electrode mixture for the positive electrode.

  When the electrode mixture is for a positive electrode and contains a positive electrode active material, the type of the positive electrode active material is not particularly limited. For example, you may select from what is normally used as a positive electrode active material of a lithium ion secondary battery. Specific examples include lithium-containing metal composite oxides, olivine-type lithium salts, chalcogen compounds, and manganese dioxide. The lithium-containing metal composite oxide is a metal oxide containing lithium and a transition metal or a metal oxide in which a part of the transition metal in the metal oxide is substituted with a different element. Examples of the different elements include Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, V, and B. Among them, Mn, Al, Co, Ni, Mg or the like is preferable. Different elements may be used alone or in combination of two or more.

The average particle size of the positive electrode active material is preferably 0.1 μm to 60 μm, and more preferably 0.5 μm to 30 μm. Further, BET specific surface area of the positive electrode active material ^is preferably 1m ² / g~10m 2 / g.

  When the electrode mixture includes a compound containing silicon as an active material and another active material, the ratio is not particularly limited. For example, the mass ratio (A: B) between the compound A containing silicon and the other active material B may be 0.5: 9.5 to 5: 5.

  The ratio of the binder and the active material contained in the electrode mixture is not particularly limited. For example, the mass ratio (A: B) between the binder A and the active material B may be 20:80 to 0.1: 99.9.

  The electrode mixture may contain a liquid medium. In particular, from the viewpoint of workability, a liquid medium is preferably contained when the binder is used (when mixed with the active material). The liquid medium contained in the electrode mixture is preferably water, but it may contain an organic solvent together with water as necessary.

The viscosity at the time of using the electrode mixture is preferably, for example, 500 mPa · s to 50000 mPa · s at 25 ° C., more preferably 1000 mPa · s to 20000 mPa · s, and 2000 mPa · s to 10000 mPa · s. More preferably it is. The viscosity is measured at 25 ° C. and a shear rate of 1.0 s ⁻¹ using a rotary shear viscometer.

  The electrode mixture may contain components other than the binder, the active material, and the liquid medium as necessary. For example, a crosslinking component to supplement the swelling resistance to the electrolyte, a rubber component to supplement the flexibility and flexibility of the electrode, a thickener to improve the coating property of the electrode mixture, and an anti-settling agent Various additives such as an agent, an antifoaming agent, and a leveling agent may be included. The state of the electrode mixture is not particularly limited and can be selected according to the storage method, the electrode formation method, and the like. For example, it may be a slurry.

<Energy device electrodes>
The electrode for an energy device according to the present disclosure includes a current collector and an electrode mixture layer that is provided on at least one surface of the current collector and includes the electrode mixture described above.
The electrode for energy devices of this indication can be used as electrodes, such as a lithium ion secondary battery, an electric double layer capacitor, a solar cell, and a fuel cell.
Hereinafter, the energy device electrode according to the present disclosure will be described in detail as applied to an electrode of a lithium ion secondary battery. However, the energy device electrode according to the present disclosure is not limited to the following contents.

The type of current collector is not particularly limited. For example, it may be selected from those commonly used in the field of lithium ion secondary batteries.
Examples of the current collector (negative electrode current collector) used for the negative electrode of the lithium ion secondary battery include sheets and foils containing stainless steel, nickel, copper, and the like. Among these, a sheet or foil containing copper is preferable. The thickness of the sheet and foil is not particularly limited, and is preferably 1 μm to 500 μm, more preferably 2 μm to 100 μm, and more preferably 5 μm from the viewpoint of ensuring the strength and workability required for the current collector. More preferably, it is ˜50 μm.
Examples of the current collector (positive electrode current collector) used for the positive electrode of the lithium ion secondary battery include sheets and foils containing stainless steel, aluminum, titanium, and the like. Among these, a sheet or foil containing aluminum is preferable. The thickness of the sheet and foil is not particularly limited, and is preferably 1 μm to 500 μm, more preferably 2 μm to 80 μm, and more preferably 5 μm from the viewpoint of ensuring the strength and workability required as a current collector. More preferably, it is ˜50 μm.

The electrode mixture layer can be formed using the electrode mixture described above. Specifically, for example, it can be formed by applying a slurry-like electrode mixture on at least one surface of the current collector, then drying and removing the solvent, and rolling as necessary.
The application of the slurry-like electrode mixture can be performed using, for example, a comma coater. The coating is suitably performed so that the ratio between the positive electrode capacity and the negative electrode capacity (negative electrode capacity / positive electrode capacity) is 1 or more in the opposing electrode. The coating amount of the slurry-like electrode mixture is, for example, dry mass per one surface of the electrode mixture layer ^is preferably from ^{5g / m 2 ~500g / m 2} , at 50g / ^{m 2} ~300g / m 2 More preferably.
The removal of the solvent is performed, for example, by drying at 50 ° C. to 150 ° C., preferably 80 ° C. to 120 ° C. for 1 minute to 20 minutes, preferably 3 minutes to 10 minutes.
Rolling is performed, for example, using a roll press machine, the density of the mixture layer, when the negative electrode mixture layer, for ^{example, 1g / cm 3 ~2g / cm} 3, preferably, 1.2 g / ^cm 3 ~ as will be 1.8 g / cm ^3, when the positive electrode material mixture layer, for ^{example, 2g / cm 3 ~5g / cm} 3, ^preferably, it is pressed so as to 2g / cm ³ ~4g / cm 3 .
Furthermore, in order to remove the residual solvent and adsorbed water in the electrode, for example, vacuum drying may be performed at 100 to 150 ° C. for 1 to 20 hours.

<Energy device>
The energy device of the present disclosure includes a positive electrode and a negative electrode, and at least one of the positive electrode and the negative electrode includes the binder and the active material described above.
Since the electrode for energy devices of this indication contains at least one of a positive electrode and a negative electrode contains the binder and active material which were mentioned above, it is excellent in cycling characteristics, even when it contains a material with large expansion and contraction as an active material.

  In an embodiment, the energy device includes at least the negative electrode including the binder and the active material described above. In one embodiment, at least the negative electrode includes the above-described binder and active material, and the energy device includes a compound containing silicon as the active material.

  Examples of the energy device of the present disclosure include a lithium ion secondary battery, an electric double layer capacitor, a solar cell, and a fuel cell. Hereinafter, although the case where the energy device is a lithium ion secondary battery will be described in detail, the energy device of the present disclosure is not limited to the following contents.

  The lithium ion secondary battery includes, for example, a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolytic solution. For details of the positive electrode and the negative electrode, reference can be made to those described in the above-mentioned energy device electrode.

  The separator is not particularly limited as long as it has ion permeability while electronically insulating between the positive electrode and the negative electrode, and has resistance to oxidation on the positive electrode side and reducibility on the negative electrode side. As a material (material) of the separator that satisfies such characteristics, a resin, an inorganic substance, or the like is used.

  As the resin, olefin polymer, fluorine polymer, cellulose polymer, polyimide, nylon and the like are used. Specifically, it is preferable to select from materials that are stable with respect to the electrolytic solution and have excellent liquid retention properties, and it is preferable to use a porous sheet made of polyolefin such as polyethylene and polypropylene, a nonwoven fabric, and the like.

Examples of inorganic substances include oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, sulfates such as barium sulfate and calcium sulfate, and glass. For example, what made the said inorganic substance of fiber shape or particle shape adhere to thin film-shaped base materials, such as a nonwoven fabric, a woven fabric, and a microporous film, can be used as a separator.
As the thin film-shaped substrate, a substrate having a pore diameter of 0.01 μm to 1 μm and a thickness of 5 μm to 50 μm is preferably used. In addition, for example, a separator in which a composite porous layer is formed using the above-described inorganic material in a fiber shape or a particle shape by using a binder such as a resin can be used as a separator. Furthermore, this composite porous layer may be formed on the surface of the positive electrode or the negative electrode to form a separator. Alternatively, this composite porous layer may be formed on the surface of another separator to form a multilayer separator. For example, a composite porous layer in which alumina particles having a 90% particle diameter (D90) of less than 1 μm are bound using a fluororesin as a binder may be formed on the surface of the positive electrode.

  The electrolytic solution contains a solute (supporting salt) and a nonaqueous solvent, and further contains various additives as necessary. The solute is usually in a dissolved state in a non-aqueous solvent. For example, the electrolytic solution is impregnated in the separator.

As the solute, those commonly used in this field can be used. Specifically, LiClO ₄ , LiBF ₄ , LiPF ₆ , LiAlCl ₄ , LiSbF ₆ , LiSCN, LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiAsF ₆ , LiB ₁₀ Cl ₁₀ , lower aliphatic lithium carboxylate, LiCl, LiBr , LiI, chloroborane lithium, borates, imide salts and the like. Examples of borates include lithium bis (1,2-benzenediolate (2-)-O, O ') and bis (2,3-naphthalenedioleate (2-)-O, O') boric acid. Lithium, bis (2,2′-biphenyldiolate (2-)-O, O ′) lithium borate, bis (5-fluoro-2-olate-1-benzenesulfonic acid-O, O ′) lithium borate Etc. Examples of imide salts include lithium bistrifluoromethanesulfonate imide ((CF ₃ SO ₂ ) ₂ NLi), lithium trifluoromethanesulfonate nonafluorobutanesulfonate ((CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ) NLi ), Lithium bispentafluoroethanesulfonate imide ((C ₂ F ₅ SO ₂ ) ₂ NLi), and the like. A solute may be used individually by 1 type, and may be used in combination of 2 or more type. The amount of solute dissolved in the non-aqueous solvent is preferably 0.5 mol / L to 2 mol / L.

  As the non-aqueous solvent, those commonly used in this field can be used. Specific examples include cyclic carbonates, chain carbonates, and cyclic carboxylic acid esters. Examples of the cyclic carbonate include propylene carbonate (PC) and ethylene carbonate (EC). Examples of the chain carbonate include diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC) and the like. Examples of the cyclic carboxylic acid ester include γ-butyrolactone (GBL) and γ-valerolactone (GVL). A non-aqueous solvent may be used individually by 1 type, and may be used in combination of 2 or more type.

  Moreover, it is preferable that a nonaqueous solvent contains vinylene carbonate (VC) from a viewpoint which can improve a battery characteristic more. When the non-aqueous solvent contains vinylene carbonate (VC), the content is preferably 0.1% by mass to 2% by mass with respect to the total amount of the non-aqueous solvent, and 0.2% by mass to 1.5%. More preferably, it is mass%.

As a configuration example of the lithium ion secondary battery, a configuration of a laminate type lithium ion secondary battery will be described below.
A laminate-type lithium ion secondary battery can be manufactured, for example, as follows. First, the positive electrode and the negative electrode are cut into squares, and tabs are welded to the respective electrodes to produce a positive electrode terminal and a negative electrode terminal. An electrode laminate is produced by laminating a separator between a positive electrode and a negative electrode, and accommodated in an aluminum laminate pack in that state, and the positive electrode terminal and the negative electrode terminal are taken out of the aluminum laminate pack and sealed. Next, an electrolytic solution is poured into the aluminum laminate pack, and the opening of the aluminum laminate pack is sealed. Thereby, a lithium ion secondary battery is obtained.

As a configuration example of the lithium ion secondary battery, a configuration of a cylindrical lithium ion secondary battery will be described below with reference to the drawings.
FIG. 1 is a cross-sectional view of a cylindrical lithium ion secondary battery. As shown in FIG. 1, the lithium ion secondary battery 1 has a bottomed cylindrical battery container 6 made of steel plated with nickel. The battery case 6 accommodates an electrode group 5 in which a strip-like positive electrode plate 2 and a negative electrode plate 3 are wound in a spiral shape with a separator 4 interposed therebetween. For example, the separator 4 has a width of 58 mm and a thickness of 30 μm. A ribbon-like positive electrode tab terminal made of aluminum and having one end fixed to the positive electrode plate 2 is led out on the upper end surface of the electrode group 5. The other end of the positive electrode tab terminal is joined by ultrasonic welding to the lower surface of a disk-shaped battery lid that is disposed on the upper side of the electrode group 5 and serves as a positive electrode external terminal. On the other hand, a ribbon-like negative electrode tab terminal made of copper with one end fixed to the negative electrode plate 3 is led out on the lower end surface of the electrode group 5. The other end of the negative electrode tab terminal is joined to the inner bottom of the battery container 6 by resistance welding. Therefore, the positive electrode tab terminal and the negative electrode tab terminal are led out to the opposite sides of the both end faces of the electrode group 5, respectively. In addition, the insulation coating which abbreviate | omitted illustration is given to the outer peripheral surface whole periphery of the electrode group 5. FIG. The battery lid is caulked and fixed to the upper part of the battery container 6 via an insulating resin gasket. For this reason, the inside of the lithium ion secondary battery 1 is sealed. In addition, an electrolyte solution (not shown) is injected into the battery container 6.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

(Synthesis Example 1)
Add 115.00 g of water to a 0.50 liter four-necked flask equipped with a stirrer, thermometer, cooling pipe, and liquid feed pump, reduce the pressure to 2.6 kPa (20 mmHg) with an aspirator, and then return to atmospheric pressure with nitrogen. The operation was repeated three times to remove dissolved oxygen. The inside of the flask was kept in a nitrogen atmosphere and heated to 75 ° C. with a water bath while stirring. 0.19 g of ammonium persulfate was dissolved in 5.00 g of water and added to the flask. Immediately after adding ammonium persulfate, 21.00 g of nitrile group-containing monomer acrylonitrile (Wako Pure Chemical Industries, Ltd.), and 19.00 g of acidic functional group-containing monomer acrylic acid (Wako Pure Chemical Industries, Ltd.) ( The mixture was added dropwise over a period of 2 hours with a liquid feed pump. Stirring was continued for 4 hours after the whole amount of the monomer was dropped. Then, it heated up at 90 degreeC over 1 hour, and obtained the resin deposit by stirring at 90 degreeC for 2 hours. The obtained resin precipitate is recovered by filtration, and then dried at 80 ° C. for 12 hours. A copolymer containing a structural unit derived from a nitrile group-containing monomer and a structural unit derived from an acidic functional group-containing monomer A dried product was obtained. After 0.1 g of the dried product obtained in a 0.2 liter flask and 9.9 g of N-methyl-2-pyrrolidone were added and dissolved, the weight average molecular weight was measured by GPC under the measurement conditions described above. It was.

(Synthesis Example 2)
Add 265.00 g of water into a 0.50 liter four-necked flask equipped with a stirrer, thermometer, cooling pipe, and liquid feed pump, reduce the pressure to 2.6 kPa (20 mmHg) with an aspirator, and then return to atmospheric pressure with nitrogen. The operation was repeated three times to remove dissolved oxygen. The inside of the flask was kept in a nitrogen atmosphere and heated to 75 ° C. with a water bath while stirring. 0.19 g of ammonium persulfate was dissolved in 5.00 g of water and added to the flask. Immediately after adding ammonium persulfate, 21.00 g of nitrile group-containing monomer acrylonitrile (Wako Pure Chemical Industries, Ltd.), and 19.00 g of acidic functional group-containing monomer acrylic acid (Wako Pure Chemical Industries, Ltd.) ( The mixture was added dropwise over a period of 2 hours with a liquid feed pump. Stirring was continued for 4 hours after the whole amount of the monomer was dropped. Thereafter, the temperature is raised to 90 ° C. over 1 hour, and the mixture is stirred at 90 ° C. for 2 hours, whereby a copolymer containing a structural unit derived from a nitrile group-containing monomer and a structural unit derived from an acidic functional group-containing monomer is obtained. A polymer dispersion was obtained. After cooling to room temperature, 2.00 g of the dispersion was weighed on an aluminum pan and heated on a hot plate at 160 ° C. for 15 minutes to obtain a dried resin composition. After 0.1 g of the dried product obtained in a 0.20 liter flask and 9.9 g of N-methyl-2-pyrrolidone were added and dissolved, the weight average molecular weight was measured by GPC under the measurement conditions described above. It was.

(Synthesis Example 3)
1. In a 0.50 liter four-necked flask equipped with a stirrer, thermometer, condenser, and liquid feed pump, 335.00 g of water and carboxymethylcellulose (Daicel Finechem Co., Ltd., trade name: CMC # 2200) as an emulsifier 21.46 g of 00 mass% aqueous solution was added, the pressure was reduced to 2.6 kPa (20 mmHg) with an aspirator, and the operation of returning to normal pressure with nitrogen was repeated three times to remove dissolved oxygen. The inside of the flask was kept in a nitrogen atmosphere and heated to 60 ° C. with a water bath while stirring. 0.26 g of ammonium persulfate was dissolved in 8.00 g of water and added to the flask. Immediately after adding ammonium persulfate, acrylonitrile (Wako Pure Chemical Industries, Ltd.) 16.98 g, butyl methacrylate (Wako Pure Chemical Industries, Ltd.) 68.26 g (total monomer amount (100 mol%) in 60 mol%) Ratio), 0.34 g of ethoxylated pentaerythritol tetraacrylate (Shin-Nakamura Chemical Co., Ltd., trade name: ATM-4E) was added dropwise over 2 hours with a feed pump. Stirring was continued for 4 hours after the whole amount of the monomer was dropped. Then, it heated up to 90 degreeC over 1 hour, and the aqueous dispersion of the copolymer was obtained by stirring at 90 degreeC for 2 hours.

<Example 1>
To the 0.20 liter flask, add 3.00 g of the dried product of the copolymer obtained in Synthesis Example 1, 0.67 g of lithium hydroxide monohydrate and 25.00 g of water as basic compounds, and stir at room temperature for 3 hours. Thus, a neutralization reaction was caused. Thereafter, water was added so that the nonvolatile content concentration was 10.00% by mass to obtain an aqueous solution of a copolymer.

Next, a graphite-based negative electrode material (Hitachi Chemical Co., Ltd., MAGE), a silicon-based negative electrode material (Hitachi Chemical Co., Ltd.), and an aqueous solution of the obtained copolymer are mixed in a solid content ratio (graphite-based negative electrode material: silicon). The negative electrode material: copolymer) is mixed to be 87.00% by mass: 10.00% by mass: 3.00% by mass, and water is added to adjust the viscosity. Got. The obtained negative electrode mixture was applied substantially uniformly and uniformly to one side of a rolled copper foil (current collector) having a thickness of 10 μm. Then, the drying process was performed and it rolled by the press and the negative electrode for evaluation was obtained. The density of the negative electrode mixture (after pressing) was 1.60 g / cm ^3, and the coating amount of the negative electrode mixture was 100.00 g / m ² .

<Examples 2 to 14>
An aqueous solution of the copolymer was obtained in the same manner as in Example 1 except that the type of copolymer and the composition of the basic compound were changed to those shown in Table 1. A negative electrode was produced in the same manner as in Example 1 using the obtained aqueous solution of the copolymer.

<Comparative Example 1>
To a 0.2 liter flask, 3.00 g of the dried product of the copolymer obtained in Synthesis Example 1 and 27.00 g of water were added and stirred at room temperature to obtain a copolymer precipitate.

Subsequently, a graphite-based negative electrode material (Hitachi Chemical Co., Ltd., MAGE), a silicon-based negative electrode material (Hitachi Chemical Co., Ltd.), and an aqueous solution of carboxymethyl cellulose (CMC: Daicel Finechem Co., Ltd., No. 2200) (nonvolatile content concentration: 1. 5 mass%) and the resulting copolymer precipitation liquid, the ratio of solid content (graphite negative electrode material: silicon negative electrode material: CMC: copolymer) is 87.00 mass%: 10.00 mass. %: 1.50% by mass: 1.50% by mass. Further, water was added for viscosity adjustment to obtain a slurry-like negative electrode mixture. The obtained negative electrode mixture was applied substantially uniformly and uniformly to one side of a rolled copper foil (current collector) having a thickness of 10 μm. Then, the drying process was performed and it rolled by the press and the negative electrode for evaluation was obtained. The density of the negative electrode mixture (after pressing) was 1.60 g / cm ^3, and the coating amount of the negative electrode mixture was 100.00 g / m ² .

<Comparative example 2>
A negative electrode was produced in the same manner as in Comparative Example 1, using the aqueous dispersion of the copolymer produced in Synthesis Example 2 as it was.

<Comparative Example 3>
A negative electrode was produced in the same manner as in Comparative Example 1, using the aqueous dispersion of the copolymer produced in Synthesis Example 3 as it was.

<Evaluation>
(1) Adhesive strength of negative electrode The prepared negative electrode was cut into a strip shape having a width of 10.00 mm and a length of 100 mm, and a double-sided tape was used to bond the mixture layer surface to the glass plate as the adherend surface. did. A sample for adhesion strength measurement is mounted on a precision universal testing machine (Shimadzu Corporation, AGS-X), 180 ° peel strength is measured at 10 mm / min, measurement distance 25 mm, and load average value between peel distances 10 mm and 20 mm Was calculated. About each negative electrode, five test pieces were measured and the average value was made into the adhesive strength (N / m) of the negative electrode. The results are shown in Table 1.

(2) Cycle characteristics In a stainless steel coin outer container with a diameter of 2.00 cm, metallic lithium cut into a circle with a diameter of 1.80 cm as a positive electrode and a polyethylene fine piece with a thickness of 20.00 μm cut into a circle with a diameter of 1.80 cm. A separator made of a porous film was arranged in this order, and an electrolyte solution (1.20 M LiPF ₆ ethylene carbonate / ethyl methyl carbonate / dimethyl carbonate = 2/2/3 volume% mixed solution + vinylene carbonate 0.80 wt%) I drew a few drops to prevent overflowing. Furthermore, a negative electrode cut into a circle with a diameter of 1.50 cm and a stainless steel plate with a thickness of 200 μm cut into a circle with a diameter of 1.60 cm as a spacer are stacked in this order, and a stainless steel cap is put through a polypropylene packing. A lithium ion secondary battery for evaluation was produced by sealing with a caulking machine for producing a coin battery.

The produced lithium ion secondary battery for evaluation was placed in a thermostatic bath at 25.00 ° C. and connected to a charge / discharge device (Toyo System Co., Ltd., TOSCAT-3200). After a constant current discharge to 0.05 V at 0.10 C, a constant voltage discharge was performed until the current value became 0.01 C at 0.05 V, and the discharge capacity was measured. Next, the battery was charged at a constant current up to 1.5 V at 0.10 C, and the charge capacity was measured. The same operation was repeated 53 times, and the cycle characteristics were calculated by the following formula. The results are shown in Table 1.
Cycle characteristics (%) = 53rd charge capacity (mAh) × 100/3 charge capacity (mAh)

As shown in Table 1, the negative electrode produced in the Example using what reacted the acidic functional group of the copolymer with the basic compound does not react the acidic functional group of the copolymer with the basic compound. Compared to the negative electrodes of Comparative Examples 1 and 2, the adhesion strength of the negative electrode was excellent, and the battery cycle characteristics were excellent. This is because the example in which the copolymer is dissolved in water has better active material coverage than Comparative Examples 1 and 2 in which the copolymer is not dissolved in water. it is conceivable that.
In Comparative Example 3, the evaluation of the adhesion strength of the negative electrode was the same as that of the example, but the cycle characteristic of the battery was lower than that of the example. This is because the copolymer dispersed in water in the form of fine particles has adhesiveness to the active material and the current collector, but the active material coating compared to the copolymer of the example dissolved in water. It is thought to be inferior in nature.

  All documents, patent applications, and technical standards mentioned in this specification are to the same extent as if each individual document, patent application, and technical standard were specifically and individually stated to be incorporated by reference, Incorporated herein by reference.

Claims (14)

  An electrode binder comprising a copolymer having a structural unit containing a nitrile group and a structural unit containing an acidic functional group, wherein at least a part of the acidic functional group forms a salt with a base.   The molar ratio of the structural unit A containing the nitrile group in the copolymer and the structural unit B containing the acidic functional group (A: B) is 1: 0.1 to 1: 1.5. The binder for electrodes according to claim 1 which is in a range.   The total ratio of the structural unit containing the nitrile group and the structural unit containing the acidic functional group in the copolymer is 95 mol% or more of all the structural units constituting the copolymer. The binder for electrodes of Claim 1 or Claim 2.   The said copolymer does not contain a hydrocarbon group in a side chain, or when it contains a hydrocarbon group in a side chain, the carbon atom number is 5 or less, The any one of Claims 1-3. Electrode binder.   The binder for electrodes of any one of Claims 1-4 whose weight average molecular weights of the said copolymer are 50,000-200,000.   The electrode binder according to any one of claims 1 to 5, further comprising water, wherein the copolymer is in a state of being dissolved in the water.   The electrode binder according to any one of claims 1 to 6, wherein the acidic functional group contains at least one selected from the group consisting of a carboxy group, a sulfo group, and a phospho group.   The structural unit having the acidic functional group is derived from at least one selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, crotonic acid, itaconic acid, citraconic acid, vinylbenzoic acid and vinylbenzenesulfonic acid. The binder for electrodes of any one of Claims 1-7.   The electrode binder according to any one of claims 1 to 8, wherein the structural unit containing the nitrile group is derived from acrylonitrile.   The binder for electrodes of any one of Claims 1-9 for formation of the electrode which contains the compound containing a silicon as an active material.   The electrode mixture containing the binder for electrodes of any one of Claims 1-10, and an active material.   The electrode mixture according to claim 11, wherein the active material contains a compound containing silicon.   The electrode for energy devices which has a collector and the electrode mixture layer which is provided on the surface of at least one of the said collector, and contains the electrode mixture of Claim 11 or Claim 12.   An energy device comprising a positive electrode and a negative electrode, wherein at least one of the positive electrode and the negative electrode comprises the binder for an electrode according to any one of claims 1 to 10 and an active material.