JP5450030B2 - Binder for aqueous electrode composition for non-aqueous secondary battery - Google Patents

Description

The present invention relates to a binder for an aqueous electrode composition for non-aqueous secondary batteries. More specifically, the present invention relates to a binder for a nonaqueous secondary battery aqueous electrode composition that can be suitably used as a binder for an electrode composition of a nonaqueous secondary battery such as a lithium ion battery.

Secondary batteries are rechargeable batteries that can be repeatedly charged and discharged. In recent years, due to the growing interest in environmental problems, not only electronic devices such as mobile phones and laptop computers, but also automobiles and airplanes. Is also in use. In response to the growing demand for secondary batteries, research is actively conducted. In particular, lithium-ion batteries that are light, small, and high in energy density are attracting attention from various industries. Development is actively underway.
A lithium ion battery is mainly composed of a positive electrode, an electrolyte, a negative electrode, and a separator, and the positive electrode is obtained by applying a positive electrode composition for a non-aqueous secondary battery onto an aluminum current collector. The positive electrode composition for a non-aqueous secondary battery mainly comprises a positive electrode active material, a conductive additive, a binder and a solvent. The binder is polyvinylidene fluoride (PVdF), and the solvent is N-methyl-2-pyrrolidone (NMP). ) Is commonly used. This is because PVdF is chemically and electrically stable, NMP is a solvent that is stable over time and dissolves PVdF, and lithium cobaltate that is generally used as a positive electrode active material is hydrolyzed in water. This is because it is necessary to use an organic solvent. However, PVdF does not have a high dissolved concentration, and is generally used at a concentration of 10% or less. When PVdF is used, it is difficult to increase the solid content concentration. Moreover, since NMP has a high boiling point, when NMP is used as a solvent, there is a problem that a large amount of energy is required for volatilization of the solvent when the positive electrode is formed. In addition, in recent years, against the backdrop of growing interest in environmental problems, water-based materials that do not use organic solvents have also been required for the positive electrode composition. Moreover, what applied the negative electrode composition for non-aqueous secondary batteries on copper foil is generally used for a negative electrode. A negative electrode composition for a non-aqueous secondary battery is mainly formed of carbon and a binder, and is required to have an electrolytic solution resistance, film adhesion, flexibility, hydrolysis resistance, and the like. As the binder, polyvinylidene fluoride (PVdF) or styrene butadiene emulsion (SBR latex) has been generally used. Under such circumstances, various researches and developments have been made on battery compositions and binders that can be used in battery compositions.

Regarding a binder that can use an aqueous solvent, a thickener for a negative electrode of a lithium ion secondary battery comprising an aqueous solution of a copolymer obtained by copolymerizing a (meth) acrylic acid polyoxyalkylene ether compound and an ethylenically unsaturated carboxylic acid, (For example, refer to Patent Document 1). In addition, regarding the binder for the battery, acrylic acid and / or methacrylic acid, an unsaturated polyalkylene glycol ester monomer having a specific structure, and a monomer copolymerizable therewith are blended at a specific ratio. It is disclosed that a carboxyl group-containing resin obtained by copolymerization is used as a battery binder resin (see, for example, Patent Document 2). Furthermore, it is a composite binder polymer for an electrode comprising a binder polymer and a dispersant chemically bonded to the surface of the binder polymer, and an alkoxy polyalkylene oxide (meth) acrylate ester having a specific structure as the dispersant Monomers, monomers derived from (meth) acrylic acid having a specific structure, reactive surfactants having a specific structure, copolymers containing these in a specific ratio, polycarboxylic acids having a specific structure A binder polymer containing at least one selected from the group consisting of system monomers is disclosed (for example, see Patent Document 3).
Further disclosed is a battery binder comprising polymer particles obtained by polymerizing a (meth) acrylic acid ester monomer, an unsaturated carboxylic acid monomer, and a vinyl monomer at a specific ratio. (For example, refer to Patent Document 4).

JP 2002-203561 A (page 1-2) JP 2003-268053 A (page 1-2) JP 2006-519883 A (Page 1-2, pages 9-14) Japanese translation of PCT publication No. 2008-537841 (1-2, 11-16)

However, the thickeners and binders disclosed in Patent Documents 1 to 4 have a (meth) acrylic acid ester monomer, but have an ester structure, and thus may not have sufficient hydrolysis resistance. There is. The thickener of Patent Document 1 is for a negative electrode composition that does not necessarily contain a lithium salt, and is actually used as a binder for an aqueous composition containing a lithium salt that may hydrolyze in water. Examples are not disclosed, and are not sufficient for use in positive electrode compositions in which lithium salts are generally used as the active material. Regarding the battery binder resin of Patent Document 2, a specific example using water as a solvent is not disclosed, and when used in a water-based positive electrode composition using water as a solvent, a sufficient function as a positive electrode is disclosed. It cannot be said that it demonstrates. Furthermore, Patent Document 3 uses LiCoO ₂ as a positive electrode active material, and it is unclear whether sufficient battery physical properties can be obtained over time. For Patent Document 4, water is disclosed as a usable dispersion medium, but in the examples, the positive electrode is made of an NMP system and has not been evaluated with an aqueous slurry. It is not clear whether the composition exhibits sufficient performance. Therefore, there has been room for devising to develop a binder capable of realizing a water-based positive electrode composition that exhibits sufficient performance as a positive electrode and has a low environmental load. Moreover, since it is preferable to use an aqueous solvent also for the negative electrode composition, a binder capable of forming an aqueous negative electrode composition is desired.

The present invention has been made in view of the above-described present situation, and includes a positive electrode that sufficiently exhibits the performance as a positive electrode for a non-aqueous secondary battery while containing a lithium salt that is said to be difficult to use in an aqueous system as an active material. An object of the present invention is to provide a binder for an aqueous electrode composition that enables realization of an aqueous positive electrode composition to be formed and that can also be suitably used for a negative electrode composition.

The present inventor, in order to realize a positive electrode composition that can form a positive electrode that exhibits sufficient performance as a positive electrode while being aqueous, focused on the binder used in the positive electrode composition, and variously studied, When a polymer having a structural unit derived from an unsaturated polyalkylene glycol ether monomer is used as a binder, hydrolysis of the binder is less likely to occur than in the case of a (meth) acrylic acid polyoxyethylene alkylene ether type. Since it can exhibit flexibility, it has been found that it can be suitably used for non-aqueous secondary batteries, and by using such a binder, the function as a positive electrode is sufficiently exerted, and non-aqueous secondary batteries are used. It has been found that a positive electrode composition that forms a positive electrode that can be suitably used for applications can be obtained, and such a vine Chromatography was also found that can also be suitably used as the binder of the anode composition. Furthermore, the present inventor said that the polymer used as the binder has a structural unit derived from an unsaturated carboxylic acid monomer in addition to a structural unit derived from an unsaturated polyalkylene glycol ether monomer. Furthermore, the present invention has been found to be suitable as a binder for an aqueous positive electrode composition, and a positive electrode formed from such a positive electrode composition will exhibit better performance as a positive electrode for a non-aqueous secondary battery. The inventors have conceived that the above problems can be solved brilliantly and have reached the present invention.

That is, the present invention is a binder used in an aqueous electrode composition for forming an electrode of a nonaqueous secondary battery, wherein the binder is a structural unit (I) derived from an unsaturated polyalkylene glycol ether monomer (a). It is a binder used for the water-system electrode composition for non-aqueous secondary batteries characterized by including the polymer which has this.
The present invention is described in detail below.

The binder of this invention is a binder used for the aqueous electrode composition which forms the electrode of a non-aqueous secondary battery, Comprising: It can be used for any of a positive electrode composition and a negative electrode composition. Below, the positive electrode composition containing the binder of this invention is described as the positive electrode composition of this invention (or the positive electrode composition for non-aqueous secondary batteries of this invention), and the negative electrode composition containing the binder of this invention is described. It describes as the negative electrode composition of this invention (or the negative electrode composition for non-aqueous secondary batteries of this invention). Moreover, the positive electrode composition and the negative electrode composition of the present invention are collectively referred to as an electrode composition of the present invention (or an electrode composition for a non-aqueous secondary battery of the present invention).

The binder of the present invention contains a polymer having the structural unit (I) derived from the unsaturated polyalkylene glycol ether monomer (a), but may contain one such polymer. Two or more types may be included. Moreover, as long as it contains such a polymer, it may contain other components.

The unsaturated polyalkylene glycol ether monomer (a) giving the structural unit (I) derived from the unsaturated polyalkylene glycol ether monomer (a) of the polymer is composed of a polymerizable ethylene group and a polyalkylene glycol. Although it will not restrict | limit especially if it has a chain | strand, following General formula (1);

^(Wherein, R 1, ^{R 2} and ^{R 3} are the same or different, .R ⁴ represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, a hydrogen atom or a straight, Represents ^a branched or cyclic hydrocarbon group, R ^a is the same or different and represents an alkylene group having 2 to 10 carbon atoms, X is a divalent alkylene group having 1 to 5 carbon atoms, or a direct bond M represents the average added mole number of the oxyalkylene group represented by R ^a O, and is preferably an integer of 2 to 200.

R ¹ , R ² and R ³ are the same or different and are a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and the alkyl group is any of linear, branched or cyclic. Also good. As an alkyl group, a C1-C8 thing is preferable. More preferably, it is a C1-C6 alkyl group, More preferably, it is a C1-C4 alkyl group.
The unsaturated polyalkylene glycol ether monomer (a) preferably has an alkenyl group having 2 to 10 carbon atoms. More preferably, it has a C3-C8 alkenyl group, More preferably, it has a C3-C6 alkenyl group. R ¹ , R ² and R ³ are preferably set appropriately so as to have such a preferable structure.

In the above general formula (1), when R ⁴ is a linear, branched or cyclic hydrocarbon group having 1 to 20 carbon atoms, R ⁴ may be methyl, ethyl, n-propyl, isopropyl, n- C 1-20 aliphatic or alicyclic alkyl groups such as butyl, isobutyl, sec-butyl, tert-butyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, etc .; phenyl, naphthyl, anthryl, phenanthryl, etc. An aryl group having 6 to 20 carbon atoms; an aryl group substituted with an alkyl group such as o-, m- or p-tolyl, 2,3- or 2,4-xylyl, and mesityl; an (alkyl) such as biphenylyl Aryl groups substituted with phenyl groups; alkyl groups substituted with aryl groups such as benzyl, phenethyl, benzhydryl, trityl, etc. That.
Among these, R ⁴ is preferably a hydrocarbon group or hydrogen atom having 10 or less carbon atoms, more preferably a hydrocarbon group or hydrogen atom having 3 or less carbon atoms, and still more preferably 2 or less carbon atoms. A saturated alkyl group, an unsaturated alkyl group, or a hydrogen atom. R ⁴ is particularly preferably a hydrogen atom, methyl, ethyl, or vinyl, and most preferably a hydrogen atom or methyl.

In the general formula (1), R ^a represents an alkylene group having 2 to 10 carbon atoms. The alkylene group may be linear or branched. The oxyalkylene groups represented by R ^a O may be the same or different. Among these, an alkylene group having 2 to 5 carbon atoms is preferable. More preferably, it is a C2-C3 alkylene group.

Specific examples of the ^Ra include ethylene (—CH ₂ CH ₂ —), trimethylene (—CH ₂ CH ₂ CH ₂ —), tetramethylene (—CH ₂ CH ₂ CH ₂ CH ₂ —), pentamethylene, A linear alkylene group such as xamethylene; ethylidene [—CH (CH ₃ ) —], propylene [—CH (CH ₃ ) CH ₂ —], propylidene [—CH (CH ₃ CH ₂ ) —], isopropylidene [ Branched chain alkylene groups such as —C (CH ₃ ) ₂ —] and the like. Among these, those having 2 to 5 carbon atoms such as ethylene, trimethylene, tetramethylene, pentamethylene, ethylidene, propylene, and isopropylidene are preferable, ethylene and propylene are more preferable, and ethylene is most preferable. That is, as the oxyalkylene group represented by R ^a O, those composed of such preferable R ^a are preferable.

In the unsaturated polyalkylene glycol ether monomer (a), the oxyalkylene group represented by R ^a O in the general formula (1) is composed of only one kind of oxyalkylene group. Also, although it may be composed of two or more different oxyalkylene groups, it is preferable that 50 to 100 mol% of the total oxyalkylene groups are composed of the above preferred oxyalkylene groups. If the oxyalkylene group is such, it will ensure solubility in water and contribute to flexibility.
The ratio of the preferable oxyalkylene group in the entire oxyalkylene group is more preferably 70 to 100 mol%, and still more preferably 80 to 100 mol%.

In the general formula (1), when X is a divalent alkylene group having 1 to 5 carbon atoms, examples of X include methylene (—CH ₂ —), ethylene (—CH ₂ CH ₂ —), trimethylene. _{(-CH 2 CH 2 CH 2 -} ), tetramethylene _{(-CH 2 CH 2 CH 2 CH} 2 -), propylene _{[-CH (CH 3) CH 2} -] , and the like. Among these, X is preferably methylene or ethylene, and particularly preferably ethylene.

In the said General formula (1), m represents the average addition mole number of the oxyalkylene group represented by R ^<a> O, and is the number of 2-200. When the oxyalkylene group represented by R ^a O has two or more different oxyalkylene groups, the addition of the oxyalkylene group may be any addition form such as random addition, block addition, and alternate addition. Good.
The average number of moles added means the average number of moles of oxyalkylene groups added in 1 mole of monomer.

When the above m exceeds 200, the polymerizability of the monomer is lowered. On the other hand, if m is less than 2, the resulting polymer does not have sufficient flexibility and may not be suitable for use as a binder. As a range of m, 2-150 are preferable and 10-100 are more preferable.

In the present invention, when the polymer having the structural unit (I) has two or more structural units represented by the general formula (1), the combination thereof is not particularly limited, but the general range of the preferred range described above A combination of compounds of formula (1) is preferred.

The unsaturated polyalkylene glycol ether monomer (a) in the present invention preferably has an alkenyl group and a polyalkylene glycol chain, and an unsaturated alcohol polyalkylene glycol adduct having an alkenyl group is preferred. is there. The monomer (a) may be a compound having a structure in which a polyalkylene glycol chain is added to an unsaturated alcohol having an alkenyl group, and has 2 to 10 carbon atoms, preferably 3 to 8 carbon atoms. While having an alkenyl group, it is preferable that the average added mole number of an oxyalkylene group having 2 to 10 carbon atoms is 2 to 200. Specifically, vinyl alcohol alkylene oxide adduct, (meth) allyl alcohol alkylene oxide adduct, 3-buten-1-ol alkylene oxide adduct, isoprenol (3-methyl-3-buten-1-ol) alkylene oxide Adduct, 3-methyl-2-buten-1-ol alkylene oxide adduct, 2-methyl-3-buten-2-ol alkylene oxide adduct, 2-methyl-2-buten-1-ol alkylene oxide adduct 2-methyl-3-buten-1-ol alkylene oxide adduct is more preferable, more preferably isoprenol (3-methyl-3-butene-1-ol obtained by adding alkylene oxide to 3-methyl-3-buten-1-ol. Buten-1-ol) alkylene oxide adduct, particularly preferably 3-methyl- - butene-1-ol 1 mol and the alkylene oxide is an average 2 to 200 mols isoprenol (3-methyl-3-buten-1-ol) alkylene oxide adducts.

The polymer having the structural unit (I) derived from the unsaturated polyalkylene glycol ether monomer (a) may further have a structural unit (II) derived from the unsaturated carboxylic acid monomer (b). preferable. When the polymer further has such a structural unit (II), the binder of the present invention is further preferred as a binder for an aqueous electrode composition, and a positive electrode formed from such an aqueous electrode composition is obtained. A more excellent function as a positive electrode for a non-aqueous secondary battery will be exhibited.
The polymer in the present invention may have one type of structural unit (II), or may have two or more types.

The unsaturated carboxylic acid monomer (b) is represented by the following general formula (2);

(Wherein R ⁵ , R ⁶ and R ⁷ are the same or different and each represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or — (CH ₂ ) _z COOM ^{2. In} this case, — (CH _{2 Z} COOM ² may form an anhydride with -COOM ¹ or other-(CH ₂ ) _z COOM ^2. In-(CH ₂ ) _z COOM ² , z is a number from 0-2. M ¹ or M ² may be the same or different and each represents a hydrogen atom, a metal atom, an ammonium group, or an organic amine group.

In the general formula (2), when R ⁵ , R ⁶ and R ⁷ are alkyl groups, the alkyl group may be linear, branched or cyclic. Moreover, as an alkyl group, a C1-C3 alkyl group is more preferable. More preferably, it is a C1 alkyl group, that is, a methyl group.

Examples of the metal atom in M ¹ or M ² include monovalent metal atoms such as alkali metal atoms such as lithium, sodium, and potassium; divalent metal atoms such as alkaline earth metal atoms such as calcium and magnesium; aluminum, Trivalent metal atoms such as iron are preferred.
The organic amine group means an organic ammonium group, that is, a protonated organic amine, and an alkanolamine group such as an ethanolamine group, a diethanolamine group, or a triethanolamine group, a dimethylamine group, or a triethylamine group is preferable. Further, it may be an ammonium group.

Among the unsaturated carboxylic acid monomers (b), examples of the unsaturated monocarboxylic acid monomers include acrylic acid, methacrylic acid, crotonic acid and the like and their monovalent metal salts, divalent metal salts, ammonium. Salts and organic ammonium salts are preferred. Among these, (meth) acrylic acid monomers, that is, acrylic acid, methacrylic acid, and monovalent metal salts, divalent metal salts, ammonium salts, and organic amine salts thereof are more preferable.

Among the unsaturated carboxylic acid monomers (b), as the unsaturated dicarboxylic acid monomer, a monomer having one unsaturated group and two groups capable of forming a carboxylic acid in the molecule, That is, maleic acid, itaconic acid, citraconic acid, fumaric acid and the like and their monovalent metal salts, divalent metal salts, ammonium salts and organic ammonium salts, and the anhydrides thereof are preferable.
In addition to these, the unsaturated carboxylic acid monomer (b) is a half ester of an unsaturated dicarboxylic acid monomer and an alcohol having 1 to 22 carbon atoms, an unsaturated dicarboxylic acid and the number of ureas. Use half amides with 1 to 22 amines, half esters of unsaturated dicarboxylic acid monomers and glycols having 2 to 4 carbon atoms, half amides of maleamic acid and glycols having 2 to 4 carbon atoms, and the like. Can do.

The polymer contained in the binder of the present invention preferably contains a structural unit in which R ⁵ , R ⁶ and R ⁷ in the general formula (2) are the same or different and are a hydrogen atom or a methyl group.
That is, the polymer contained in the binder of the present invention preferably contains a structural unit derived from an unsaturated monocarboxylic acid monomer. Electrolytic solution resistance improves that it contains the structural unit derived from an unsaturated monocarboxylic acid-type monomer.

The proportion of the structural unit derived from the unsaturated monocarboxylic acid monomer is 0.000% with respect to 100% by mass of the entire structural unit represented by the general formula (2) contained in the polymer contained in the binder of the invention. It is preferable that it is 1-50 mass%. More preferably, it is 1-30 mass%, More preferably, it is 3-25 mass%.

The polymer contained in the binder of the present invention essentially has the structural unit (I) derived from the unsaturated polyalkylene glycol ether monomer (a), and the structure derived from the unsaturated carboxylic acid monomer (b). Although it is preferable to have unit (II), you may have structural unit (III) derived from other monomers other than these.

As the monomer (c) forming the structural unit (III) derived from the above other monomers, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, (meth) acrylic (Meth) acrylic acid alkyl esters such as butyl acid; hydroxyalkyl (meth) acrylates such as hydroxyethyl (meth) acrylate and hydroxybutyl (meth) acrylate; 2-methylpropanesulfonic acid (meth) acrylamide, styrene sulfonic acid, etc. Unsaturated sulfonic acids; and monovalent metal salts, divalent metal salts, ammonium salts and organic amine salts thereof; unsaturated amides such as (meth) acrylamide and (meth) acrylalkylamide; vinyl acetate, vinyl propionate, etc. Of vinyl esters; aromatic vinyls such as styrene It is. As the monomer (c) that forms the structural unit (III) derived from other monomers, one or more kinds can be used.

The polymer in the present invention essentially contains the structural unit (I) and may have the structural unit (II) and the structural unit (III). The mass ratio of these structural units (the structural unit ( I) / (II) / (III)) is preferably 50 to 100% by mass / 0 to 50% by mass / 0 to 49% by mass. More preferably, it is 50-99 mass% / 1-50 mass% / 0-49 mass%, More preferably, it is 50-97 mass% / 3-25 mass% / 0-20 mass%.

The polymer contained in the binder of the present invention preferably has a weight average molecular weight of 10,000 to 300,000. When the molecular weight is within such a range, the filler can be bound and the viscosity can be kept within the coatable range. More preferably, it is 13,000-200000, More preferably, it is 15000-100,000.
The weight average molecular weight of the polymer can be determined, for example, by GPC (gel permeation chromatography) measurement under the following measurement conditions.
Measuring instrument: Waters LCM1
Molecular weight column: G4000SWXL, G3000SWXL, 2000SWXL (all manufactured by Tosoh Corporation) connected in series Eluent: 10999 g water, 6001 g acetonitrile dissolved in sodium acetate dianhydride 115.6 Standard substance for calibration curve: polyethylene Glycol measurement method: Measure the one that is dissolved in the eluent so that the solid content of the measurement object is 0.3% by mass and filtered through a filter.

In the positive electrode composition of the present invention, the binder content is preferably 2 to 10% by mass with respect to 100% by mass of the positive electrode active material. When the content of the binder is within this range, it is possible to bind the positive electrode active material and the conductive additive and to suppress the decrease in the amount of the active material.

The polymer contained in the binder of the present invention can be synthesized by a method such as solution polymerization or bulk polymerization. The solution polymerization can be carried out batchwise or continuously, and the solvent used in this case is water; alcohol such as methyl alcohol, ethyl alcohol, isopropyl alcohol; benzene, toluene, xylene, cyclohexane, n-hexane, etc. Preferred are aromatic or aliphatic hydrocarbons; ester compounds such as ethyl acetate; ketone compounds such as acetone and methyl ethyl ketone; and cyclic ether compounds such as tetrahydrofuran and dioxane. Among these, it is preferable to use at least one selected from the group consisting of water and a lower alcohol having 1 to 4 carbon atoms because of the solubility of these raw material monomers and the resulting copolymer. Is more preferable in that the solvent removal step can be omitted.

In the case of carrying out the aqueous solution polymerization, as a radical polymerization initiator, a water-soluble polymerization initiator, for example, a persulfate such as ammonium persulfate, sodium persulfate, potassium persulfate; hydrogen peroxide; 2,2'-azobis- Azoamidine compounds such as 2-methylpropionamidine hydrochloride, cyclic azoamidine compounds such as 2,2′-azobis-2- (2-imidazolin-2-yl) propane hydrochloride, and azonitriles such as 2-carbamoylazoisobutyronitrile It is preferable to use a water-soluble azo initiator such as a compound. At this time, Fe (II) salt such as alkali metal sulfite such as sodium hydrogen sulfite, metabisulfite, sodium hypophosphite, and molle salt, sodium hydroxymethanesulfinate dihydrate, hydroxylamine hydrochloride, thio Accelerators such as urea, L-ascorbic acid (salt), and erythorbic acid (salt) can also be used in combination. Among these, a combination of hydrogen peroxide (H ₂ O ₂ ) and an accelerator such as L-ascorbic acid (salt) is preferable. These radical polymerization initiators and accelerators may be used alone or in combination of two or more.
The initiator H ₂ O ₂ mole number may be 1.0 to 10.0 mol% with respect to the total mole number of the monomers (a), (b) and (c), but preferably 2. It is 0-4.0 mol%, More preferably, it is 2.0-3.0 mol%, The optimal is 2.0-2.5 mol%.
Initiator L- ascorbic acid moles _is sufficient if 0.1 to 10 times the H 2 _{O 2,} preferably 0.1 to 0.4 times, more preferably 0.15 to 0.35 Times, most preferably 0.2 to 0.3 times.
Although the reaction temperature at the time of manufacturing the polymer of this invention should just be 30-90 degreeC, when using said initiator, 55-65 degreeC is optimal for reaction temperature.

In addition, when performing solution polymerization using a lower alcohol, aromatic or aliphatic hydrocarbon, ester compound or ketone compound as a solvent, or when performing bulk polymerization, benzoyl peroxide, lauroyl peroxide, sodium peroxide, etc. Peroxides such as t-butyl hydroperoxide and cumene hydroperoxide; azo compounds such as azobisisobutyronitrile are used as radical polymerization initiators. In this case, an accelerator such as an amine compound can be used in combination. Furthermore, when a water-lower alcohol mixed solvent is used, it can be appropriately selected from the above-mentioned various radical polymerization initiators or combinations of radical polymerization initiators and accelerators.

It is preferable that the usage-amount of all the monomer components in the said polymerization is 30 mass% or more with respect to the whole raw material containing another raw material. If the amount of all monomer components used is too lower than this range, it is not preferable because the polymerization rate is lowered and the productivity is lowered. More preferably, it is 30-70 mass%, More preferably, it is 30-60 mass%, Most preferably, it is 40-60 mass%.

As a method for charging each monomer into the reaction vessel, the whole amount is initially charged into the reaction vessel, the whole amount is divided into the reaction vessel or continuously charged, a part is initially charged into the reaction vessel, and the rest Any of the methods of dividing or continuously charging to the reaction vessel may be used. As a preferable charging method, specifically, a method in which the whole amount of the monomer (a) is initially charged into the reaction vessel and the monomer (b) is continuously charged into the reaction vessel, the monomer (a) and A method of continuously charging all of the monomer (b) into the reaction vessel, a part of the monomer (a) is initially charged into the reaction vessel, and the remainder of the monomer (a) and the monomer (b ) Or a part of the monomer (a) and a part of the monomer (b) are initially charged into the reaction container, and the monomer (a) And the remainder of the monomer (b) are alternately divided into several times in a reaction vessel. Furthermore, by changing the charging rate of each monomer into the reaction vessel during the reaction continuously or stepwise, the charging mass ratio of each monomer per unit time can be changed continuously or stepwise. You may make it synthesize | combine the mixture of the copolymer from which the ratio of structural unit (I) and structural unit (II) in a polymer differs in a polymerization reaction. The radical polymerization initiator may be charged into the reaction vessel from the beginning, may be dropped into the reaction vessel, or these may be combined according to the purpose.

A chain transfer agent can also be used in combination for adjusting the molecular weight of the resulting polymer. Chain transfer agents include mercaptoethanol, thioglycerol, thioglycolic acid, 3-mercaptopropionic acid, thiomalic acid, 2-mercaptoethanesulfonic acid and other thiol chain transfer agents; isopropyl alcohol and other secondary alcohols; phosphorous acid Hypophosphorous acid and salts thereof (sodium hypophosphite, potassium hypophosphite, etc.), sulfurous acid, hydrogen sulfite, dithionic acid, metabisulfite and salts thereof (sodium sulfite, sodium hydrogen sulfite, dithione) Known hydrophilic chain transfer agents such as sodium oxide, sodium metabisulfite and the like lower oxides and salts thereof can be used. Furthermore, in order to adjust the molecular weight of the polymer, it is also effective to use a monomer having a high chain transfer property such as (meth) allylsulfonic acid (salt) as the monomer (c).
The number of moles of chain transfer agent may be 0.1 to 20 mol%, preferably 1.0 to 4.0 moles, based on the total number of moles of monomers (a), (b) and (c). %, More preferably 1.5 to 3.0 mol%, and most preferably 1.8 to 2.5 mol%.

In the reaction for obtaining the above polymer, in order to obtain a polymer having a predetermined molecular weight with good reproducibility, it is necessary to allow the polymerization reaction to proceed stably. The dissolved oxygen concentration in is preferably 5 ppm or less. Preferably it is 0.01-4 ppm, More preferably, it is 0.01-2 ppm, Most preferably, it is 0.01-1 ppm. In addition, when nitrogen substitution etc. are performed after adding a monomer to a solvent, it is preferable to make the dissolved oxygen concentration of the system | strain containing a monomer into the said range.

The polymer obtained by the above polymerization is used as an essential component of the binder of the present invention as it is, but it is preferable to adjust the pH to 5 or more from the viewpoint of handleability. However, when the polymerization is carried out at a pH of 5 or higher, the polymerization rate is lowered, and at the same time, the polymerizability becomes worse. The pH can be adjusted using inorganic salts such as monovalent and divalent metal hydroxides and carbonates; ammonia; one or more alkaline substances such as organic amines. Further, after the reaction is completed, the concentration can be adjusted if necessary.
pH measurement can measure the value of 25 degreeC, for example using glass electrode type hydrogen ion thermometer F-21 (Horiba, Ltd.).

The binder of the present invention is a binder that can form an aqueous positive electrode composition containing the polymer as described above and using water as a solvent, and a positive electrode formed from the positive electrode composition thus obtained. Can be suitably used for non-aqueous secondary batteries. The binder of the present invention is a binder capable of forming a water-based negative electrode composition, and the negative electrode formed from the negative electrode composition thus obtained is also preferably used for a non-aqueous secondary battery. It is something that can be done.
An aqueous electrode composition comprising a binder and water as essential components and forming an electrode of a nonaqueous secondary battery, wherein the binder is an aqueous electrode for a nonaqueous secondary battery constituted by the binder of the present invention. A composition is also one aspect of the present invention.
The aqueous electrode composition for a non-aqueous secondary battery of the present invention is a homogeneous composition containing a binder dissolved in water, so that the binding property between a positive electrode active material and a conductive additive described later can be improved. Is also excellent. Unlike emulsions, emulsions that are often used conventionally as binders are generally about 50 to 400 nm particles. In the positive electrode composition of the present invention, as will be described later, the particle diameters of the positive electrode active material and the conductive additive are preferably 1 μm or less, more preferably about several hundred nm, and those having such particle diameters are used. When dispersed, the size is almost similar to that of the emulsion particles. As a result, the emulsion particles adhere to each other with dots. However, as the particle size decreases, the number of fillers increases, the number of points to be bound increases, and a large amount of binder may be required. On the other hand, when a homogeneous binder is used, the polymer tends to spread on the surface of the filler particles, and it becomes easy to adhere to other fillers (active material and conductive aid) in the surroundings, and it is relatively easy to obtain a binding property.
In addition, in an electrode composition using PVdF as a binder and NMP as a solvent, it is difficult to increase the solid content concentration, and it takes time to dry and it is necessary to collect NMP. Since the electrode composition of the present invention can increase the solid content concentration and is an aqueous composition, it dries faster and does not require solvent recovery compared to NMP as a solvent. Furthermore, the positive electrode film and the negative electrode film obtained from the electrode composition of the present invention are excellent in film strength that does not cause chipping or peeling on the cut surface during cutting. From these things, the aqueous electrode composition for non-aqueous secondary batteries of this invention is a suitable thing as a composition which forms a positive electrode or a negative electrode.

The positive electrode composition forming the positive electrode for a non-aqueous secondary battery exhibits a function as a positive electrode by including a positive electrode active material and a conductive additive in addition to a binder and water. That is, the electrode is a positive electrode, and the aqueous electrode composition for a non-aqueous secondary battery further contains a positive electrode active material and a conductive additive. One of the preferred embodiments of the object.
Moreover, the negative electrode composition forming the negative electrode for the non-aqueous secondary battery includes a negative electrode active material, and, if necessary, a conductive auxiliary agent, a dispersant, etc. in addition to a binder and water, so that it functions as a negative electrode. Will be demonstrated. That is, the electrode is a negative electrode, and the aqueous electrode composition for a non-aqueous secondary battery further contains a negative electrode active material and water. The aqueous electrode composition for a non-aqueous secondary battery of the present invention is also included. This is one of the preferred embodiments.

The positive electrode active material preferably has an average particle size of 1 μm or less. By using a positive electrode active material having an average particle size of 1 μm or less, it is possible to improve electrical characteristics such as output characteristics when the positive electrode composition for non-aqueous secondary batteries is used as a positive electrode of a battery. . The average particle diameter is more preferably 0.01 to 0.8 μm, and still more preferably 0.03 to 0.5 μm.
The average particle size of the positive electrode active material can be measured by, for example, a dynamic light scattering particle size distribution meter.

The compound that can be used as the positive electrode active material may be any lithium-containing metal oxide that can reversibly insert and remove lithium ions.

The positive electrode active material in the present invention preferably contains a compound having an olivine structure. The compound having an olivine structure is represented by the following formula:
Li _x A _y D _z PO ₄
(However, A is one or more selected from the group consisting of Cr, Mn, Fe, Co, Ni and Cu, and D is Mg, Ca, Sr, Ba, Ti, Zn, B, It is one or more selected from the group consisting of Al, Ga, In, Si, Ge, Sc, Y and rare earth elements, where x, y and z are 0 <x <2, 0 <y <1.5. And a number satisfying 0 ≦ z <1.5.). When such a positive electrode active material is used, an oxygen atom in the structure is bonded to phosphorus to form a (PO ₄ ) ^3- polyanion, and oxygen is immobilized in the crystal structure in principle. Since the combustion reaction does not occur and the safety is excellent, it is preferable in consideration of the use for a medium-sized and large-scale power source. The A component is preferably Fe, Mn, or Ni, and particularly preferably Fe. The D component is preferably Mg, Ca, Ti, or Al.
Of the compounds that can be used as the positive electrode active material of the present invention, the compound having an olivine structure is lithium iron phosphate, lithium manganese phosphate, or the like, and the positive electrode active material preferably contains these compounds. Further, as the positive electrode active material, it is preferable to use a material whose surface is partially or entirely covered with carbon in order to supplement conductivity. The coating amount of carbon is preferably 20 parts by weight or less, and more preferably 10 parts by weight or less with respect to 100 parts by weight of the positive electrode active material.
When the positive electrode active material includes a compound having an olivine structure, the compound having an olivine structure is preferably 70% by mass or more with respect to 100% by mass of the entire positive electrode active material. More preferably, it is 90% by mass or more, and most preferably, the positive electrode active material is composed of only a compound having an olivine structure.

The positive electrode active material in the present invention preferably contains lithium iron phosphate as a main component. The compound contained in the positive electrode active material is more preferably lithium iron phosphate among the compounds having the olivine structure, and is preferably the main component of the positive electrode active material. Lithium iron phosphate has high stability against overcharge and uses abundant resources such as iron and phosphorus, so it is inexpensive and preferable in terms of manufacturing cost. Further, lithium iron phosphate is also preferable from this point because hydrolysis is difficult to occur even when an aqueous solvent is used.
The phrase “containing lithium iron phosphate as a main component” means that the content of lithium iron phosphate is 100% by mass or more with respect to 100% by mass of the whole positive electrode active material, preferably 80% by mass or more, More preferably, it is 90 mass% or more. Most preferably, the positive electrode active material consists only of lithium iron phosphate.

In the positive electrode composition for a non-aqueous secondary battery of the present invention, the content of the conductive additive is preferably 2 to 25% by mass with respect to 100% by mass of the positive electrode active material. When there is less content of a conductive support agent than 2 mass%, there exists a possibility that electrode resistance cannot be reduced and the effect of mixing a conductive support agent may not be obtained. On the other hand, when the amount is more than 25% by mass, the amount of the active material contained in the positive electrode is reduced, so that it is difficult to secure capacity. More preferably, it is 5-15 mass% with respect to 100 mass% of positive electrode active materials.

The conductive auxiliary agent preferably has an average particle size of 1 μm or less. By using a positive electrode active material having an average particle size of 1 μm or less, it is possible to improve electrical characteristics such as output characteristics when the positive electrode composition for non-aqueous secondary batteries is used as a positive electrode of a battery. . The average particle diameter is more preferably 0.01 to 0.8 μm, and still more preferably 0.03 to 0.5 μm.
The average particle diameter of the conductive auxiliary agent can be measured by, for example, a dynamic light scattering particle size distribution meter (conducting auxiliary agent refractive index is set to 2.0).

The conductive aid is used to increase the output of the lithium ion battery, and conductive carbon is mainly used.
Examples of the conductive carbon include carbon black, fiber carbon, and graphite. Of these, ketjen black and acetylene black are preferred.
Ketjen Black has a hollow shell structure and easily forms a conductive network. Therefore, it is preferable because the equivalent performance is exhibited with an addition amount about half that of conventional carbon black. Further, acetylene black is preferred because carbon black produced by using a high purity acetylene gas has very few impurities and surface crystallites are developed.

The positive electrode composition for a non-aqueous secondary battery of the present invention preferably further uses a dispersant. When a dispersant is used, the dispersant is not particularly limited, and various dispersants such as an anionic, nonionic or cationic surfactant, or a polymer dispersant can be used. A more stable conductivity of the positive electrode film can be achieved by promoting the formation of fine particles of the positive electrode active substance and the conductive additive and improving the dispersibility by the dispersant.

It is preferable that the positive electrode composition for non-aqueous secondary batteries of this invention contains 5-20 mass% of dispersing agents with respect to 100 mass% of conductive support agents. When the content of the dispersant is in such a range, the positive electrode active material and the conductive additive can be sufficiently uniformly dispersed. More preferably, it is 6-15 mass% with respect to 100 mass% of conductive support agents.

The positive electrode composition for a non-aqueous secondary battery of the present invention may further contain a thickener. As will be described later, the binder of the present invention also exhibits an action as a thickener. However, the positive electrode composition for a non-aqueous secondary battery of the present invention is a thickener other than the binder of the present invention. May be included. As the thickener, methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropoxycellulose, carboxymethylcellulose (CMC), carboxymethylcellulose sodium salt (CMC-Na), sodium polyacrylate, and the like can be used.
In the positive electrode composition for a non-aqueous secondary battery of the present invention, the thickener can be appropriately adjusted and used so that the viscosity of the positive electrode composition for a non-aqueous secondary battery falls within a preferable range described later.

The positive electrode composition for a non-aqueous secondary battery of the present invention is a water-based positive electrode composition using water as a solvent, and the water content in the composition is 50 to 100% by mass of the positive electrode active material. It is preferable that it is 300 mass%. When the water content is within this range, a slurry having an appropriate viscosity can be produced. More preferably, it is 70-200 mass%.

The positive electrode composition of the present invention may contain components other than those described above. When components other than those mentioned above are included, the content is preferably such that the solid content ratio of the positive electrode composition falls within the following preferred range.

In the positive electrode composition for a non-aqueous secondary battery of the present invention, the solid content is preferably 35 to 70% by mass with respect to 100% by mass of the entire positive electrode composition. More preferably, it is 40-60 mass%. The solid content of the positive electrode composition is a component remaining after the solvent is volatilized from the positive electrode composition, that is, a component other than the solvent in the positive electrode composition.

The positive electrode active material, the conductive auxiliary agent, the binder, and the content ratio of other components other than these three components in the solid content of the positive electrode composition for a non-aqueous secondary battery of the present invention are positive electrode active material / conductive auxiliary agent / Binder / Others = 70-95 / 2-20 / 2-10 / 0-5 is preferable. With such a content ratio, it becomes possible to make excellent electrical characteristics such as output characteristics when the positive electrode composition for non-aqueous secondary battery is used as the positive electrode of the battery. More preferably, they are 80-93 / 3-3-15 / 4-10 / 0-3. In addition, the other component here means the component contained in solid content other than a positive electrode active material, a conductive support agent, a binder, and a dispersing agent, a thickener, etc. are contained.

As the negative electrode active material contained in the aqueous negative electrode composition for non-aqueous secondary batteries of the present invention, those generally used as negative electrode active materials can be used. Examples of the negative electrode active material include carbonaceous materials such as amorphous carbon, graphite, natural graphite, and artificial graphite, polyacene conductive polymers, composite metal oxides such as lithium titanate, and silicon such as SiOx (0 ≦ x <2). Examples of the negative electrode composition, other metal oxides, lithium metal, and lithium alloy.
The negative electrode composition forming the negative electrode for a non-aqueous secondary battery can contain a conductive additive, a dispersing agent, a thickener and the like as required in addition to a binder, water, and a negative electrode active material. As a conductive support agent, a dispersing agent, and a thickener, the thing similar to the thing in the positive electrode composition mentioned above can be used by the same content. The water content and solid content ratio in the aqueous negative electrode composition for non-aqueous secondary batteries of the present invention are also the same as those of the aqueous positive electrode composition for non-aqueous secondary batteries of the present invention.

The content ratio of the negative electrode active material, the conductive additive, the binder and other components in the solid content of the negative electrode composition for a non-aqueous secondary battery of the present invention is 85 to 99/0 to 10/1 to 10/0 to 5. Preferably there is. More preferably, it is 92-99 / 0-3 / 1-5 / 5-0. In addition, other components here mean components other than a negative electrode active material, a conductive support agent, and a binder, and a dispersing agent, a thickener, etc. are contained.

The electrode composition for a non-aqueous secondary battery of the present invention preferably has a viscosity of 1 to 20 Pa · s. When the viscosity of the electrode composition for a non-aqueous secondary battery is in such a range, it is possible to ensure appropriate fluidity at the time of coating. More preferably, it is 3-15 Pa * s, More preferably, it is 4-10 Pa * s.
Moreover, it is preferable that the thixo value of the electrode composition for non-aqueous secondary batteries of this invention is 2.5-8. When it is 2.5 or less, the coating liquid flows and becomes easy to repel, and when it is 8 or more, the coating liquid does not have fluidity and is difficult to apply. More preferably, it is 3-6.
The viscosity of the electrode composition for non-aqueous secondary batteries can be measured, for example, with a B-type viscometer.
The thixo value can be obtained by, for example, measuring the viscosity at 25 ± 1 ° C., 6 rpm and 60 rpm with a B-type viscometer, and dividing the viscosity at 6 rpm by the viscosity at 60 rpm.

The electrode composition for a non-aqueous secondary battery of the present invention preferably has a pH of 6-9. When the pH is in such a range, the aluminum current collector is hardly corroded, and the battery performance of the material can be sufficiently exhibited.
The pH can be measured by the same method as described above.

When the aqueous electrode composition for non-aqueous secondary batteries of the present invention is used as a positive electrode composition, the average particle size when the refractive index of the filler component is 1.7 using a particle size measuring device for dynamic light scattering. It is preferable that a diameter is 0.1-1 micrometer. When the average particle diameter when the electrode composition for non-aqueous secondary battery is in a slurry state is in such a range, it can be confirmed that the filler component is sufficiently refined and mixed. When the average particle diameter is larger than 1 μm, dispersion is insufficient, and when a positive electrode formed from such a composition is used, battery performance may be deteriorated. The average particle diameter is more preferably 0.15 to 0.8 μm, and still more preferably 0.2 to 0.5 μm.

In the case where the positive electrode composition for a non-aqueous secondary battery includes a positive electrode active material and a conductive additive, the positive electrode active material and the conductive additive are uniformly dispersed as a method for producing the positive electrode composition. Although it does not restrict | limit as much as possible, a dispersing agent is mixed with water which is a solvent, and then a conductive additive is mixed and dispersed using beads, a ball mill, a stirring mixer, etc., and dissolved or dispersed in water there. It is preferable to add a positive electrode active material and perform a dispersion treatment in the same manner to obtain a positive electrode composition for a non-aqueous secondary battery. When the composition is prepared by such a procedure, it is preferable that the positive electrode active material and the conductive additive are sufficiently uniformly dispersed.
The negative electrode composition for nonaqueous secondary batteries is also preferably prepared by the same method except that the negative electrode active material is used instead of the positive electrode active material.

The positive electrode composition for a non-aqueous secondary battery of the present invention is formed from the positive electrode composition using the binder of the present invention in a positive electrode composition that uses water as a solvent but may be hydrolyzed in water. The positive electrode can exhibit sufficient performance as a positive electrode for a non-aqueous secondary battery.
Such a positive electrode member for a non-aqueous secondary battery formed using the aqueous electrode composition for a non-aqueous secondary battery of the present invention is also one aspect of the present invention. Furthermore, a secondary battery configured using such a positive electrode member for a non-aqueous secondary battery is also one aspect of the present invention.
Moreover, the negative electrode formed from the negative electrode composition using the binder of this invention can exhibit sufficient performance as a negative electrode for non-aqueous secondary batteries. The negative electrode member for a non-aqueous secondary battery formed using such an aqueous electrode composition for a non-aqueous secondary battery of the present invention is also one aspect of the present invention. Furthermore, a secondary battery constructed using such a negative electrode member for a non-aqueous secondary battery is also one aspect of the present invention.

The secondary battery using the positive electrode member for non-aqueous secondary battery formed using the aqueous electrode composition for non-aqueous secondary battery of the present invention has an initial discharge capacity of the positive electrode active material of 120 mAh / g or more. Is preferred. More preferably, it is 130 mAh / g or more.
Further, the secondary battery using the non-aqueous secondary battery negative electrode member formed using the non-aqueous secondary battery aqueous electrode composition of the present invention has an initial discharge capacity when the negative electrode active material is a carbonaceous material. Is preferably 200 mAh / g or more. More preferably, it is 250 mAh / g or more, More preferably, it is 300 mAh / g or more.
Here, the initial discharge capacity is the discharge capacity for the first charge / discharge.
Moreover, it is preferable that the secondary battery of this invention is 90% or more of the electrical capacity maintenance factor after 50 cycles which repeated charging / discharging 50 times. More preferably, it is 95% or more, More preferably, it is 97% or more. By confirming the maintenance rate of 50 cycles, it can be confirmed that the dispersant does not adversely affect the initial battery physical properties.
The electric capacity of the secondary battery can be measured by a charge / discharge evaluation apparatus or the like.

The binder of the present invention includes a polymer having the structural unit (I) derived from the unsaturated polyalkylene glycol ether monomer (a), and can be used as a binder and also has a thickening effect. Even if the polymer having the structural unit (I) derived from the unsaturated polyalkylene glycol ether monomer (a) is used as a thickener, it can be used as a thickener. When the function as a binder is exhibited, it corresponds to the use of the binder of the present invention.
In addition, the use of the polymer having the structural unit (I) derived from the unsaturated polyalkylene glycol ether monomer (a) in a state in which only the function as a thickener is exhibited is also a technical idea of the present invention. Within range. That is, the thickener containing the polymer having the structural unit (I) derived from the unsaturated polyalkylene glycol ether monomer (a) is also one aspect of the present invention.

The binder used in the aqueous electrode composition for a non-aqueous secondary battery of the present invention has the above-described configuration, and can form a positive electrode composition using water as a solvent, and is difficult to use in an aqueous system. While including a lithium salt as an active material, it sufficiently exhibits the performance as a positive electrode for a non-aqueous secondary battery, and can also be suitably used as a binder for a negative electrode composition. It is a binder that can realize an electrode composition that balances the considerations for and the performance as a positive electrode and a negative electrode for a non-aqueous secondary battery.

The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to these examples. Unless otherwise specified, “part” means “part by weight” and “%” means “mass%”.

(1) Binder Synthesis Example Synthesis Example 1: Binder (I) -1
A reactor equipped with a thermometer, a stirrer, a dripping device, a nitrogen introduction tube and a reflux cooling device was charged with an average of 50 moles of ethylene oxide added to 41.14 g of ion-exchanged water and 3-methyl-3-buten-1-ol. After charging 49.37 g of a saturated polyalkylene glycol ether monomer (IPN50), the reactor was purged with nitrogen under stirring, and the temperature was raised to 60 ° C. in a nitrogen atmosphere. .86 g was added, and an aqueous solution composed of 5.90 g of acrylic acid and 1.48 g of ion-exchanged water was added dropwise over 3 hours.
Simultaneously with this dropping, an aqueous solution composed of 0.26 g of 3-mercaptopropionic acid, 0.10 g of L-ascorbic acid and 15.91 g of ion-exchanged water was dropped over 3.5 hours. Then, after maintaining the temperature of 60 degreeC continuously for 1 hour, it cooled and complete | finished superposition | polymerization.
Thereafter, a pH of about 6 and a solid content of 40 wt% were adjusted using a 48 wt% sodium hydroxide aqueous solution and ion-exchanged water at 30 ° C. to obtain an aqueous solution of a binder.
The weight average molecular weight of the obtained binder was 36300.
The weight average molecular weight was measured by GPC (gel permeation chromatography) under the following conditions.
Measuring instrument: Waters LCM1
Molecular weight column: G4000SWXL, G3000SWXL, 2000SWXL (all manufactured by Tosoh Corporation) connected in series Eluent: 10999 g water, 6001 g acetonitrile dissolved in sodium acetate dianhydride 115.6 Standard substance for calibration curve: polyethylene Glycol measurement method: A solution in which the solid content of the measurement object was dissolved in the eluent so as to be 0.3% by mass and filtered through a filter was measured.

Synthesis Example 2: Binder (I) -2
A reactor equipped with a thermometer, a stirrer, a dripping device, a nitrogen inlet tube and a reflux cooling device was charged with 44.66 g of ion-exchanged water and an average of 50 mol of ethylene oxide added to 3-methyl-3-buten-1-ol. Charge 49.37 g of a saturated polyalkylene glycol ether monomer (IPN50), purge the reactor with nitrogen under stirring, raise the temperature to 60 ° C. in a nitrogen atmosphere, and then add 2% aqueous hydrogen peroxide 2 .39 g was added, and an aqueous solution composed of 3.15 g of acrylic acid and 0.79 g of ion-exchanged water was added dropwise over 3 hours.
Simultaneously with this dropping, an aqueous solution composed of 0.13 g of 3-mercaptopropionic acid, 0.06 g of L-ascorbic acid and 15.91 g of ion-exchanged water was dropped over 3.5 hours. Then, after maintaining the temperature of 60 degreeC continuously for 1 hour, it cooled and complete | finished superposition | polymerization.
Thereafter, a pH of about 6 and a solid content of 40 wt% were adjusted using a 48 wt% sodium hydroxide aqueous solution and ion-exchanged water at 30 ° C. to obtain an aqueous solution of a binder.
When the weight average molecular weight of the obtained binder was measured by the same method as for binder (I) -1, the weight average molecular weight was 37700.

Synthesis Example 3: Binder (I) -3
A reactor equipped with a thermometer, a stirrer, a dripping device, a nitrogen introduction tube and a reflux cooling device was charged with an average of 50 moles of ethylene oxide added to 42.43 g of ion-exchanged water and 3-methyl-3-buten-1-ol. After charging 49.37 g of a saturated polyalkylene glycol ether monomer, the inside of the reactor was purged with nitrogen under stirring, and the temperature was raised to 60 ° C. in a nitrogen atmosphere. Then, 4.12 g of a 2% aqueous hydrogen peroxide solution was added thereto. Then, an aqueous solution composed of 3.11 g of acrylic acid, 5.90 g of 2-hydroxyethyl acrylate, and 2.26 ion-exchanged water was added dropwise over 3 hours. Simultaneously with this dropping, an aqueous solution composed of 0.33 g of 3-mercaptopropionic acid, 0.11 g of L-ascorbic acid and 15.91 g of ion-exchanged water was dropped over 3.5 hours. Then, after maintaining the temperature of 60 degreeC continuously for 1 hour, it cooled and complete | finished superposition | polymerization.
Thereafter, a pH of about 7 and a solid content of 40 wt% were adjusted using a 48 wt% sodium hydroxide aqueous solution and ion-exchanged water at 30 ° C. to obtain an aqueous solution of a binder.
When the weight average molecular weight of the obtained binder was measured by the same method as for binder (I) -1, the weight average molecular weight was 31900.

(2) Preparation Example 1 of Positive Electrode Composition
Phosphoric acid coated with 1.50 g of acetylene black HS-100 (manufactured by Denka) and carbon after adding 3.75 g of 40 wt% (I) -1 binder aqueous solution to 35.55 g of water to make a uniform solution. Iron lithium (imported in China) was added and dispersed in the order of 27.00 g, followed by filtration to obtain a positive electrode composition (1).

Example 2
A positive electrode composition (2) was obtained in the same manner as in Example 1 except that 41.55 g of water, 3.00 g of acetylene black HS-100, and 25.50 g of lithium iron phosphate coated with carbon were changed to 25.50 g. .

Example 3
2. 35.25 g of water and 40 wt% aqueous binder solution of (I) -2
Except having changed to 75 g, it carried out similarly to Example 1 and obtained the positive electrode composition (3).

Example 4
A positive electrode composition (4) was obtained in the same manner as in Example 1 except that 35.25 g of water and the aqueous binder solution were changed to 3.75 g of 40 wt% (I) -3 binder aqueous solution.

Example 5
After adding 20.79 g of water and 1.11 g of Discoat N-14 (for a 27% concentration product) to make a uniform solution, 3.00 g of acetylene black HS-100 and 25 iron phosphate lithium coated with carbon were added. .50 g was added and dispersed, and then 40 wt% (I) -1 aqueous binder solution (3.00 g) was added and dispersed, followed by filtration to obtain a positive electrode composition (5).

Example 6
A positive electrode composition (6) was obtained in the same manner as in Example 5 except that the binder aqueous solution was changed to 3.00 g of a 40 wt% (I) -2 binder aqueous solution.

Comparative Example 1
After adding 20.36 g of water and 1.11 g of DISCOAT N-14 to make uniform, 3.00 g of acetylene black HS-100 and 25.50 g of lithium iron phosphate coated with carbon were added and dispersed, 35 wt% Of polyacrylic acid sodium (Mw100,000) 3.43 g was added and dispersed, followed by filtration to obtain a comparative positive electrode composition (1).

Comparative Example 2
After adding 17.89 g of water and 1.11 g of Discoat N-14 to make uniform, 3.00 g of acetylene black HS-100 and 25.50 g of lithium iron phosphate coated with carbon are added and dispersed, and SBR latex (Product with a solid content of 48%) 2.50 g was added and dispersed, followed by filtration to obtain a comparative positive electrode composition (2).

(3) Various evaluations of positive electrode composition Positive electrode compositions (1) to (6) obtained in Examples 1 to 6 and Comparative positive electrode compositions (1) and (2) obtained in Comparative Examples 1 and 2 ) Was evaluated. The evaluation method is as follows. The evaluation results are shown in Table 1. In Table 1, in the blending composition, in addition to the amount and total amount of each component, the amount of solid content therein is also shown. For example, the amount of binder (I) -1 in Example 1 (3.75 / 1.50) was added to 3.75 g of 40 wt% (I) -1 aqueous binder solution, and the solid content of the binder was added therein. 1.50g is included.
In Table 1, PAA-Na represents sodium polyacrylate.
1. The positive electrode composition 0.5g was put into the solid content aluminum pan, and it dried at 150 degreeC for 1 hour using the hot air dryer. The mass of the solid content was measured from the weight before and after drying.
2. A viscosity B type viscometer (manufactured by Tokyo Keiki Co., Ltd.) was used to measure the viscosity at 25 ± 1 ° C. and 30 rpm.
3. Using a thixo value B type viscometer (manufactured by Tokyo Keiki Co., Ltd.), the viscosity at 25 ± 1 ° C., 6 rpm and 60 rpm was measured, and the value obtained by dividing the viscosity at 6 rpm by the viscosity at 60 rpm was determined.
4). pH
A value of 25 ° C. was measured using a glass electrode type hydrogen ion thermometer F-21 (manufactured by Horiba, Ltd.).

5. The average particle size was measured using a particle size measuring device LB-500 (manufactured by Horiba, Ltd.).
The value was calculated on the assumption that the filler refractive index of the positive electrode composition was 1.7.
Measurement temperature: 25 ° C. Measurement solvent: water Film strength (preparation of positive electrode film)
The positive electrode composition was coated on an aluminum foil using an applicator. The film was dried at 100 ° C. for 10 minutes and 150 ° C. for 60 minutes, and further subjected to hot pressing at 150 ° C. for 30 minutes to produce a positive electrode film having a thickness of about 40 μm.
(Film strength evaluation)
When the positive electrode film was punched with a 12 mm punch, it was judged from the ease of chipping or peeling of the cut surface. ○ ・ ・ ・ No chipping or peeling △ ・ ・ ・ Sometimes chipping or peeling at the cut end
X: The punched edge is always chipped and peeled off. A positive electrode film was prepared in the same manner as in the charge / discharge test film strength evaluation, and battery evaluation was performed using a coin cell using a charge / discharge measurement apparatus ACD-001 (manufactured by Asuka Electronics Co., Ltd.).
Positive electrode: prepared positive electrode film Negative electrode: Li foil electrolyte: 1 mol% / L LiPF ₆ EC / EMC = 1/1 (manufactured by Kishida Chemical Co., Ltd.)
Charging / discharging conditions: 0.2C

(4) Preparation Example 7 of Negative Electrode Composition
30.0 g of carboxymethyl cellulose (CMC) (# 1380 manufactured by Daicel) adjusted to 1% was mixed with 6.28 g of water, and 29.25 g of graphite CGB-10 (manufactured by Nippon Graphite Co., Ltd.) was added and dispersed. 1.13 g of binder (I) -1 was added, mixed and dispersed, and filtered to obtain a negative electrode composition (1).

Example 8
Except having changed the binder of Example 7 from (I) -1 to (I) -3, it carried out similarly to Example 7 and obtained the negative electrode composition (2).

(5) Various Evaluations of Negative Electrode Composition The obtained negative electrode composition was subjected to solid content, viscosity, thixo value, pH, film strength evaluation and charge / discharge test. Measurements of solid content, viscosity, thixo value, and pH were performed in the same manner as the positive electrode composition. The evaluation of the film strength and the charge / discharge test were performed as follows. The results are shown in Table 2.
1. Film strength (preparation of negative electrode film)
The negative electrode composition was applied on the Cu night using an applicator. The film was dried at 100 ° C. for 10 minutes and 150 ° C. for 60 minutes, and further subjected to hot pressing at 150 ° C. for 30 minutes to produce a negative electrode film of about 40 μm.
(Film strength evaluation)
The film strength was evaluated in the same manner as in the case of the positive electrode film.
2. A negative electrode film was prepared in the same manner as in the charge / discharge test film strength evaluation, and battery evaluation was performed using a coin cell using a charge / discharge measurement apparatus ACD-001 (manufactured by Asuka Electronics Co., Ltd.).
Positive electrode: Prepared negative electrode film Negative electrode: Li foil electrolyte: 1 mol% / L LiPF ₆ EC / EMC = 1/1 (manufactured by Kishida Chemical Co., Ltd.)
Charging / discharging conditions: 0.2C

From the comparison between Examples and Comparative Examples, the polymer was given flexibility by having the structural unit (I), and the film strength was improved. Moreover, it was confirmed from the comparison with Example 5, 6 and the comparative example 1 that a coating-material viscosity falls, handling property improves, and the outstanding battery performance is exhibited. In addition, when compared under the same conditions, a result that the rate of decrease in the discharge capacity was smaller than that in the case of using SBR latex with a proven record in the negative electrode as a binder was obtained. Further, from the results of Examples 7 and 8, the negative electrode produced using the binder of the present invention had good film strength and exhibited excellent electrical properties. Was confirmed to be suitable as a material for the negative electrode composition.

Claims (11)

A binder used in an aqueous electrode composition forming an electrode of a non-aqueous secondary battery,
The binder for use in an aqueous electrode composition for a non-aqueous secondary battery, comprising a polymer having a structural unit (I) derived from an unsaturated polyalkylene glycol ether monomer (a). The binder used for the aqueous electrode composition for nonaqueous secondary batteries according to claim 1, wherein the polymer further has a structural unit (II) derived from the unsaturated carboxylic acid monomer (b). . A water-based electrode composition comprising a binder and water as essential components and forming an electrode of a non-aqueous secondary battery,
This binder is comprised with the binder used for the water-system electrode composition for non-aqueous secondary batteries of Claim 1 or 2, The water-system electrode composition for non-aqueous secondary batteries characterized by the above-mentioned. The said electrode is a positive electrode, The said water-system electrode composition for non-aqueous secondary batteries further contains a positive electrode active material and a conductive support agent, The water for non-aqueous secondary batteries of Claim 3 characterized by the above-mentioned. -Based electrode composition. The said positive electrode active material contains the compound which has an olivine structure, The water-system electrode composition for non-aqueous secondary batteries of Claim 4 characterized by the above-mentioned. The water-based electrode composition for a non-aqueous secondary battery according to claim 4 or 5, wherein the positive electrode active material contains lithium iron phosphate as a main component. The nonaqueous secondary battery aqueous electrode composition has an average particle diameter of 0.1 to 1 μm when the refractive index of the filler component is 1.7 using a particle diameter measuring device for dynamic light scattering. The aqueous electrode composition for a non-aqueous secondary battery according to any one of claims 3 to 6. The aqueous electrode for a non-aqueous secondary battery according to claim 3, wherein the electrode is a negative electrode, and the aqueous electrode composition for a non-aqueous secondary battery further contains a negative electrode active material and water. Composition. A positive electrode member for a non-aqueous secondary battery, which is formed using the aqueous electrode composition for a non-aqueous secondary battery according to claim 3. A negative electrode member for a non-aqueous secondary battery, which is formed using the aqueous electrode composition for a non-aqueous secondary battery according to claim 3 or 8. A secondary battery comprising the positive electrode member for a non-aqueous secondary battery according to claim 9 or the negative electrode member for a non-aqueous secondary battery according to claim 10.