JPWO2017164041A1 - Electrode binder composition, electrode slurry, electrode and battery using them - Google Patents

Abstract

SUMMARY The present invention provides a binder composition for an electrode, an electrode slurry, an electrode and a battery using the same, which can obtain long-term reliability, that is, a high capacity retention ratio and initial charge / discharge efficiency when used as a battery. For the purpose. The present invention provides a binder composition for an electrode comprising (a) at least one resin selected from the following (a-1) to (a-3) and (b) a basic compound. (A-1) Polyhydroxystyrene resin (a-2) Polystyrene resin having at least one selected from a carboxyl group and a sulfonic acid group in the side chain (a-3) Phenolic resin

Description

  The present invention relates to a binder composition. Specifically, the present invention relates to an electrode binder composition, an electrode slurry, an electrode using them, and a battery.

In recent years, with the explosive spread of notebook personal computers and small portable terminals, there has been an increasing demand for rechargeable secondary batteries having a small size, light weight, high capacity, high energy density, and high reliability.
In the automobile industry, there are high expectations for reducing carbon dioxide emissions by introducing electric vehicles (EVs) and hybrid electric vehicles (HEVs), and the development of secondary batteries for motor drives that hold the key to their practical application. It is actively done.

  In particular, lithium ion secondary batteries, which are said to have the highest theoretical energy among batteries, are attracting attention, and are currently being developed rapidly. Lithium ion batteries currently in widespread use include positive electrode active materials such as lithium cobalt oxide and other composite oxides containing lithium and secondary battery electrode binders such as polyvinylidene fluoride (PVDF) (hereinafter abbreviated as binder) A positive electrode formed by applying a slurry for a secondary battery electrode (hereinafter may be abbreviated as slurry) on an aluminum foil, and a carbon-based electrode active material (hereinafter abbreviated as active material). The negative electrode formed by applying a slurry containing a negative electrode active material capable of occluding and releasing lithium ions and a binder such as PVDF or styrene / butadiene / rubber (SBR) onto a copper foil is used as a separator and an electrolyte layer. And has a sealed configuration.

  Secondary battery electrode binder composition (hereinafter may be abbreviated as electrode binder composition) is obtained by dissolving a substance used as a secondary battery electrode binder in an organic solvent, or dispersed in an organic solvent or water. It has been made. A slurry for a secondary battery electrode, which is a mixture obtained by mixing an electrode active material with this electrode binder composition, is made of, for example, aluminum or aluminum by the blade method, dipping method, reverse roll method, direct roll method, knife method, spin coating method, or the like. An electrode is manufactured by applying to a current collector such as copper and removing the solvent by a method such as drying to bind the active material to the current collector and bind the active materials together. The manufactured positive / negative electrode is wound up with a separator made of, for example, a porous polypropylene, and a battery is manufactured through other steps.

  The capacity of the battery is determined by a plurality of factors such as the type and amount of the active material and the type and amount of the electrolytic solution, but the performance of the electrode binder composition is also an important factor. If the electrode binder composition can bind a sufficient amount of active material to the current collector and the active materials cannot be bonded to each other, a battery having a large initial capacity cannot be obtained, and the current collection is performed by repeating charge and discharge. The active material is dropped from the body, and the capacity of the battery is reduced. In recent years, particularly in the negative electrode, it has been studied to use silicon, germanium, tin or an alloy thereof as an active material for the purpose of increasing the capacity of the negative electrode (for example, see Patent Document 1).

In addition, an organic solvent binder composition in which PVDF, which is an existing electrode binder composition, is dissolved in N-methylpyrrolidone or the like, and an electrode binder composition in which a rubber polymer is dispersed in water have been proposed ( For example, see Patent Documents 2 to 5).
Furthermore, by using a polyimide-based resin as a binder, it is possible to suppress a decrease in capacity in a long-term cycle test even for a silicon-containing negative electrode having a large volume change during charge and discharge (see, for example, Patent Documents 6 to 8). It has been reported.

JP 2009-199761 A JP-A-6-203833 Japanese Patent Laid-Open No. 5-62668 JP-A-4-342966 JP-A-8-124557 JP 2009-245773 A JP 2010-062041 A JP 2009-170384 A

  However, when silicon, germanium, tin, or an alloy thereof is used as the active material, the lithium ion occlusion amount per unit volume is larger than that of the conventionally used carbon-based material, but is sufficiently charged. There was a problem that the volume change of the active material itself was large when the discharge was sufficiently performed.

  In addition, an organic solvent-based binder composition in which PVDF, which is an existing electrode binder composition, is dissolved in N-methylpyrrolidone or the like, and an electrode binder composition in which a rubber-based polymer is dispersed in water have a volume of active material. There was a problem that the high capacity could not be maintained for a long time due to the deterioration of the binding force due to repeated charging and discharging, which could not follow the change.

  Furthermore, although the polyimide binder composition has high cycle performance, there is a problem that the initial charge / discharge efficiency is lower than that of PVDF or rubber polymer.

  In view of the above problems, the present invention provides a battery that uses silicon, tin, germanium, or an alloy thereof as a negative electrode to obtain a long-term reliability, that is, a high capacity retention rate, as well as a high initial charge / discharge efficiency. An object is to provide a binder composition, an electrode slurry, an electrode using the same, and a battery.

The present invention is an electrode binder composition comprising (a) at least one resin selected from the following (a-1) to (a-3) and (b) a basic compound.
(A-1) Polyhydroxystyrene resin (a-2) Polystyrene resin having at least one selected from a carboxyl group and a sulfonic acid group in the side chain (a-3) Phenolic resin

  ADVANTAGE OF THE INVENTION According to this invention, when it is set as a battery, long-term reliability, ie, a high capacity | capacitance maintenance factor, can be obtained, the binder composition for electrodes with high initial stage charge / discharge efficiency, the slurry for electrodes, and the electrode using this are obtained. Can do. In addition, a battery having a high capacity retention rate and initial charge / discharge efficiency can be obtained.

The present invention is an electrode binder composition comprising (a) at least one resin selected from the following (a-1) to (a-3) and (b) a basic compound.
(A-1) Polyhydroxystyrene resin (a-2) Polystyrene resin having at least one selected from a carboxyl group and a sulfonic acid group in the side chain (a-3) Phenolic resin

  Examples of the (a-1) polyhydroxystyrene resin used in the present invention include p-hydroxystyrene, m-hydroxystyrene, o-hydroxystyrene, p-isopropenylphenol, m-isopropenylphenol, o-iso. A polymer obtained by polymerizing an aromatic vinyl compound having a phenolic hydroxyl group such as propenylphenol, alone or in a known manner, or a copolymer of the aromatic vinyl compound and another vinyl compound Coalescence is mentioned.

  In addition, the (a-1) polyhydroxystyrene resin used in the present invention is an alkyl group having 1 to 20 carbon atoms, a fluoroalkyl group, an alkoxyl group, an ester group, a part of hydrogen atoms bonded to an aromatic ring, A structure substituted with 1 to 4 fluorine atoms or chlorine atoms may also be used.

  Examples of the polystyrene resin having at least one selected from a carboxyl group and a sulfonic acid group in the side chain (a-2) used in the present invention include p-carboxystyrene, m-carboxystyrene, o-carboxystyrene, p -Polymers obtained by polymerizing aromatic vinyl compounds having a carboxyl group or a sulfonic acid group such as sulfonated styrene, m-sulfonated styrene, o-sulfonated styrene, etc., alone or in a known manner. Or a copolymer of the aromatic vinyl compound and another vinyl compound.

  In addition, the polystyrene resin having at least one selected from a carboxyl group and a sulfonic acid group in the side chain (a-2) used in the present invention has a part of hydrogen atoms bonded to an aromatic ring having 1 to 1 carbon atoms. A structure in which 1 to 4 alkyl groups, fluoroalkyl groups, alkoxyl groups, ester groups, fluorine atoms, or chlorine atoms are substituted by 20 or the like may be used.

  The preferred weight average molecular weight of a polystyrene resin having at least one selected from a carboxyl group and a sulfonic acid group in the side chain (a-2) used in the present invention is measured using gel permeation chromatography (GPC). It is preferably in the range of 1,000 to 100,000, preferably 2,000 to 30,000 in terms of polystyrene.

  Examples of the (a-3) phenolic resin used in the present invention include novolak resins and resol resins. These can be obtained by polycondensing various phenols alone or a mixture of a plurality of them with aldehydes such as formalin by a known method.

  Examples of the phenols constituting the novolak resin and the resol resin include phenol, p-cresol, m-cresol, o-cresol, 2,3-dimethylphenol, 2,4-dimethylphenol, 2,5-dimethylphenol, 2 , 6-dimethylphenol, 3,4-dimethylphenol, 3,5-dimethylphenol, 2,3,4-trimethylphenol, 2,3,5-trimethylphenol, 3,4,5-trimethylphenol, 2,4 , 5-trimethylphenol, methylene bisphenol, methylene bis p-cresol, resorcin, catechol, 2-methyl resorcin, 4-methyl resorcin, o-chlorophenol, m-chlorophenol, p-chlorophenol, 2,3-dichlorophenol, m-methoxyph Nord, p-methoxyphenol, p-butoxyphenol, o-ethylphenol, m-ethylphenol, p-ethylphenol, 2,3-diethylphenol, 2,5-diethylphenol, p-isopropylphenol, α-naphthol, (beta) -naphthol etc. are mentioned, These can be used individually or as a mixture of several.

  In addition to formalin, examples of aldehydes include paraformaldehyde, acetaldehyde, benzaldehyde, hydroxybenzaldehyde, chloroacetaldehyde, and the like. These can be used alone or as a mixture of a plurality of them.

  Moreover, (a-3) phenol resin used by this invention is a C1-C20 alkyl group, a fluoroalkyl group, an alkoxyl group, an ester group, a fluorine atom, a part of hydrogen atom couple | bonded with the aromatic ring, Alternatively, a structure in which 1 to 4 chlorine atoms are substituted may be used.

  The preferred weight average molecular weight of the (a-3) phenol resin used in the present invention is 2,000 to 50,000, preferably 3,000 to 30 in terms of polystyrene measured using gel permeation chromatography (GPC). , Preferably in the range of 1,000.

  From the viewpoint of improving the capacity retention rate during charge / discharge of the battery, the preferred resin (a) is a polyhydroxystyrene resin having a structure represented by the following general formula (1).

(In General Formula (1), R ¹ and R ² represent an organic group or halogen having 1 to 5 carbon atoms. Preferred organic groups having 1 to 5 carbon atoms are alkyl groups, alkenyl groups, alkynyl groups, and fluoroalkyl groups. R ³ represents a monovalent organic group having 1 to 20 carbon atoms, and preferred examples of the organic group having 1 to 20 carbon atoms include an alkyl group, an alkenyl group, an alkynyl group, or one of them. Examples include those in which the above hydrogen is substituted with a hydroxyl group, a methacryloxy group, an acryloxy group, or a glycidyl ether group, and R ⁴ , R ⁵ , and R ^{6 each} represent a hydrogen atom or an organic group having 1 to 3 carbon atoms. Examples of the organic group having 1 to 3 include an alkyl group or a fluoroalkyl group, a is an integer of 0 to 4, c is an integer of 0 to 5, b is an integer of 1 to 5, and a + b is 1 to 5 Is an integer .n ₁ is an integer of 10 to _10000, n 2, _{n 3} is an integer of 0 to 10,000, which is _{0.2 ≦ n 1 / (n 1} + n 2 + n 3) ≦ 1.)

The resin represented by the general formula (1) is composed of n ₁ hydroxystyrene monomers, n ₂ styrene monomers, and n ₃ other vinyl compounds. n ₁ is an integer of 10 to 10,000, n ₂ and n ₃ are integers of 0 to 10,000, and 0.2 ≦ n ₁ / (n ₁ + n ₂ + n ₃ ) ≦ 1. In addition, 0.4 ≦ n ₁ / (n ₁ + n ₂ + n ₃ ) ≦ 1 is preferable, and 0.7 ≦ n ₁ / (n ₁ + n ₂ + n ₃ ) ≦ 1 is more preferable. Most preferably, 0.9 ≦ n ₁ / (n ₁ + n ₂ + n ₃ ) ≦ 1. A higher proportion of the hydroxystyrene-based monomer having a phenolic hydroxyl group is preferable because the binder has a stronger binding power and has the advantage of improving the capacity retention rate during charge and discharge.

  Preferred as other vinyl compounds are conjugated diene monomers, ethylenically unsaturated carboxylic acid ester monomers, glycidyl group-containing vinyl monomers, and sulfonic acid group-containing vinyl monomers.

  Specific examples of other preferable vinyl compounds include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, methyl acrylate, ethyl acrylate, propyl acrylate, Butyl acrylate, butyl acrylate, n-amyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, 2-hydroxyethyl acrylate, hydroxypropyl acrylate, methacrylic acid Propyl, butyl methacrylate, isobutyl methacrylate, n-amyl methacrylate, isoamyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, n-octyl methacrylate, 2-hydroxyethyl methacrylate, hydroxy methacrylate Cypropyl, lauryl acrylate, lauryl methacrylate, methyl crotonic acid, ethyl crotonic acid, ethyl isocrotonate, methyl methacrylate, ethyl methacrylate, acrylic acid, methacrylic acid, maleic acid, fumaric acid, citraconic acid, methaconic acid, glutaconic acid , Itaconic acid, tetrahydrophthalic acid, crotonic acid, isocrotonic acid, nadic acid, monooctyl maleate, monobutyl maleate, monooctyl itaconic acid, styrene, α-methylstyrene, β-methylstyrene, pt-butylstyrene, And chlorostyrene.

  The weight average molecular weight of the polyhydroxystyrene-based resin used in the present invention is preferably in the range of 3,000 to 60,000 in terms of polystyrene measured using gel permeation chromatography (GPC), and 3,000. More preferably, it is in the range of ˜25,000.

  In the present invention, (a-3) a phenol resin and (a-1) a polyhydroxystyrene resin can be used in combination. From the viewpoint of improving the capacity retention rate during charge and discharge of the battery, the content ratio of the (a-1) polyhydroxystyrene resin at the time of combined use is preferably as large as possible. A preferable content ratio of (a-3) phenol resin and (a-1) polyhydroxystyrene resin is 50:50 to 0: 100 in terms of mass ratio.

The resin (a) may be used alone or in a blend with other resins for the purpose of improving charge / discharge characteristics or adjusting viscosity.
Preferred as other resins are resins that are combinations of other vinyl compounds suitable for the above-mentioned copolymerization, and more specifically, polyacrylic acid, polymethacrylic acid, polyoxyethylene, poly (2-methoxyethoxy). Ethylene), polyvinyl alcohol, polyvinyl sulfonic acid, polyvinylidene fluoride, polysaccharides such as amylose, amylopectin, starch, and carboxymethyl cellulose.

  More preferable as the other resin is a cellulose compound represented by the following general formula (3) from the viewpoint of improving the capacity retention rate during charging and discharging of the battery.

(In General Formula (3), R ¹⁸ represents hydrogen or CH ₂ COOR ^19, and a plurality of R ¹⁸ may be the same or different. R ¹⁹ represents hydrogen, lithium, sodium, or potassium, and R ¹⁹ may be the same or different, and n ₇ represents an integer of 10 to 100,000.)

  The content of the other resin is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, from the viewpoint of improving the capacity retention rate during charging / discharging of the battery with respect to 100 parts by mass of the resin (a). More preferably, it is 20 parts by mass or more. Further, the content of the other resin is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and still more preferably from 100 parts by mass of the resin (a) from the viewpoint of improving the heat resistance of the electrode. Is 30 parts by mass or less.

  The binder composition of the present invention contains (b) a basic compound. (B) Examples of basic compounds include organic nitrogen-containing compounds such as tertiary amines, pyridine derivatives and tetraalkylammonium salts, hydroxide compounds containing alkali metals and alkaline earth metals, hydrogenated compounds, and carbonate compounds. An inorganic base compound etc. are mentioned.

  (B) Preferred specific examples of the basic compound include triethylamine, tributylamine, ethanolamine, diethanolamine, triethanolamine, triisopropanolamine, pyridine, hydroxypyridine, methylpyridine, methoxypyridine, sodium hydroxide, potassium hydroxide, Examples thereof include lithium hydroxide, calcium hydroxide, magnesium hydroxide, sodium carbonate, potassium carbonate, lithium carbonate, calcium carbonate, and sodium bicarbonate.

From the viewpoint of improving the capacity retention rate during charge / discharge of the battery, the basic compound (b) is more preferably a base containing at least one element selected from alkali metals and alkaline earth metals, most preferably alkaline. A base containing a metal. (B) The most preferred specific examples of the basic compound include sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium carbonate, potassium carbonate, lithium carbonate, and sodium bicarbonate.
These basic compounds and the phenolic hydroxyl group, carboxyl group, and sulfonic acid group in the side chain of the resin (a) form an ionic bond. Due to ionization of the side chain, the spread of the molecular chain is increased, and the adhesiveness of the ionic functional group improves the binding property of the filler as a binder used in the electrode.

  (B) The preferable addition amount of the basic compound is 5 mol% or more, more preferably 30 mol% or more, more preferably 100 mol% of the total of phenolic hydroxyl group, carboxyl group and sulfonic acid group of the resin (a). Preferably it is 50 mol% or more. By being in this range, the binding force of the binder for electrodes is strong, and there is an advantage of improving the capacity retention rate during charging and discharging of the battery. Moreover, the preferable addition amount of (b) a basic compound is 300 mol% or less with respect to 100 mol% of phenolic hydroxyl groups of resin which has a phenolic hydroxyl group, More preferably, it is 200 mol% or less, More preferably, it is 100 mol% or less. Most preferably, it is 90 mol% or less. By being in this range, there is an advantage that the deterioration of the electrode due to the basic compound can be suppressed, and the capacity retention rate at the time of charge / discharge of the battery is improved.

  From the viewpoint of improving the capacity retention rate during charging and discharging of the battery, the binder composition of the present invention preferably contains a thermal crosslinking agent. As the thermal crosslinking agent, epoxy compounds, methylol compounds, methoxymethyl compounds, divinylbenzene, and the like are preferably used. Among these, in order to maintain the strength of the binder, it is more preferable to use methylol or a methoxymethyl compound.

  Preferable specific examples of the epoxy compound include, for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, epoxy group-containing silicone such as polymethyl (glycidyloxypropyl) siloxane, etc. The present invention is not limited to these at all. Specifically, “Epicron” (registered trademark) 850-S, Epicron HP-4032, Epicron HP-7200, Epicron HP-820, Epicron HP-4700, Epicron EXA-4710, Epicron HP-4770, Epicron EXA-859CRP , Epicron EXA-1514, Epicron EXA-4880, Epicron EXA-4850-150, Epicron EXA-4850-1000, Epicron EXA-4816, Epicron EXA-4822 (trade name, manufactured by Dainippon Ink & Chemicals, Inc.), “Lika Resin” (registered trademark) BEO-60E (trade name, manufactured by Shin Nippon Rika Co., Ltd.), EP-4003S, EP-4000S (trade name, manufactured by Adeka Co., Ltd.), and the like.

  Preferred examples of methylol compounds and methoxymethyl compounds include, for example, DML-PC, DML-PEP, DML-OC, DML-OEP, DML-34X, DML-PTBP, DML-PCHP, DML-OCHP, DML-PFP, DML-PSBP, DML-POP, DML-MBOC, DML-MBPC, DML-MTrisPC, DML-BisOC-Z, DML-BisOCHP-Z, DML-BPC, DML-BisOC-P, DMOM-PC, DMOM-PTBP, DMOM-MBPC, TriML-P, TriML-35XL, TML-HQ, TML-BP, TML-pp-BPF, TML-BPE, TML-BPA, TML-BPAF, TML-BPAP, TMOM-BP, TMOM-BPE, TMOM-B A, TMOM-BPAF, TMOM-BPAP, HML-TPPHBA, HML-TPHAP, HMOM-TPPHBA, HMOM-TPHAP (above trade name, manufactured by Honshu Chemical Industry Co., Ltd.), or lithium, sodium, potassium ionized products thereof, “NIKALAC” (registered trademark) MX-290, NIKACALAC MX-280, NIKACALAC MX-270, NIKACALAC MX-279, NIKACAL MW-100LM, NIKACALAC MX-750LM It is done. Two or more of these may be contained.

  Among the thermal crosslinking agents of the present invention, in particular, the methoxymethyl compound represented by the following general formula (2) is water-soluble, and thus is well compatible with the composition component containing the resin (a) and the base compound (b). In order to further increase the capacity retention rate during charge and discharge, it can be most preferably used.

(In the general formula (2), R ¹³ , R ¹⁴ and R ¹⁵ may be the same or different and each represents hydrogen or a monovalent metal cation. R ¹⁶ and R ¹⁷ may be the same or different. , Represents hydrogen or an organic group having 1 to 3 carbon atoms.)

In the general formula (2), R ¹³ , R ¹⁴ , and R ¹⁵ represent at least one element selected from hydrogen and a monovalent metal cation, and 10 relative to 100 mol% in total of R ¹³ , R ^14, and R ^15. More than mol% is a monovalent metal cation. An alkali metal is preferable as the metal cation, and Na, Li, and K are more preferable.
From the viewpoint of improving the capacity retention rate during charge and discharge of the battery, as the introduction amount of the metal cations, the total 100 mole% of R ^13, R ¹⁴ and R ^15, more preferably is 20 mol% or more More preferred is 50 mol% or more.

R ¹⁶ and R ¹⁷ represent at least one selected from hydrogen and an organic group having 1 to 3 carbon atoms. Preferred examples of the organic group having 1 to 3 carbon atoms include an alkyl group, an alkenyl group, an alkynyl group, a fluoroalkyl group, and an alkoxyl group.

  The content of the thermal cross-linking agent is preferably 0.1 parts by mass or more, more preferably 1 part by mass or more, from the viewpoint of improving the capacity retention rate during charging / discharging of the battery with respect to 100 parts by mass of the whole resin. More preferably, it is 2 parts by mass or more. From the viewpoint of improving the flexibility of the electrode, the content of the thermal crosslinking agent is preferably 30 parts by mass or less with respect to 100 parts by mass of the entire resin. More preferably, it is 20 mass parts or less, More preferably, it is 10 mass parts or less.

Furthermore, a photoacid generator or a thermal acid generator may be added to the binder composition of the present invention in order to promote cross-linking of the above-described epoxy compound, methylol compound, and methoxymethyl compound.
The thermal acid generator preferably has a thermal decomposition starting temperature of 50 ° C. to 270 ° C., more preferably 50 ° C. to 150 ° C.
Specific examples of the thermal acid generator include onium salts such as sulfonium salts, ammonium salts, and phosphonium salts, and a compound having a structure represented by the following general formula (4) is preferable.

In General Formula (4), R ²⁰ represents at least one selected from an organic group having 1 to 8 carbon atoms and a hydroxyl group. Preferred examples of the organic group having 1 to 8 carbon atoms include an alkyl group having 1 to 8 carbon atoms and an ester group having 1 to 4 carbon atoms. R ²¹ and R ²² represent an organic group having 1 to 16 carbon atoms. R ²¹ and R ²² preferably contain at least one aromatic ring having 6 to 16 carbon atoms, hydrogen in the aromatic ring is unsubstituted, or an alkyl group having 1 to 4 carbon atoms, or a fluoroalkyl group having 1 to 4 carbon atoms , A hydroxyl group, a halogen, a cyano group, a nitro group, a group substituted with a nitroso group, or an alkyl group having 1 to 10 carbon atoms. R ²³ represents at least one selected from an alkyl group having 1 to 8 carbon atoms and a fluoroalkyl group having 1 to 8 carbon atoms.

  Particularly preferable examples of the thermal acid generator include, but are not limited to, those having the following structures.

  The binder composition of the present invention may further comprise a surfactant, a silane coupling agent such as aminopropyltrimethoxysilane, trimethoxyvinylsilane, trimethoxyglycidoxysilane, triazine compound, phenanthroline compound, triazole, if necessary. You may contain 0.1-10 mass parts of system compounds etc. with respect to 100 mass parts of total amounts of resin. By containing these, adhesiveness with an active material and metal foil can further be improved.

  The binder composition for electrodes of the present invention may be used as a solution. The range of the concentration and viscosity of the binder solution is preferably in the range of 1 mPa · sec to 1000 Pa · sec at a concentration of 1 to 50% by mass, more preferably in the range of 100 mPa · sec to 100 Pa · sec at a concentration of 5 to 30% by mass. .

Examples of the solvent used in the binder solution include water, NMP, DMAC, DMF, DMSO, GBL, propylene glycol dimethyl ether, ethyl lactate, cyclohexanone, tetrahydrofuran, propylene glycol monomethyl ether acetate, various alcohols, methyl ethyl ketone, methyl isobutyl ketone, and the like. be able to.
From the viewpoint of safety, it is preferable that 80% or more of the solvent is water.

The binder composition for electrodes of the present invention can also be used as a slurry for electrodes containing the binder composition for electrodes of the present invention and a filler.
Preferred fillers for use in secondary batteries and electric double layer capacitors include carbon, silicon, tin, germanium, titanium, iron, cobalt, nickel, manganese, copper, silver, zinc, indium, bismuth, antimony or chromium. Examples include compounds containing atoms. Preferably, it is a compound containing at least one atom of carbon, manganese, cobalt, nickel, iron, silicon, titanium, tin, and germanium, more preferably at least one of silicon, silicon oxide, and lithium titanate. It is a compound containing types.

  When these compounds are used as a filler, the filler plays a role as an active material. For this reason, it can use as a slurry for electrodes of a secondary battery or an electric double layer capacitor by adding a filler to the resin of the present invention to form a slurry.

Examples of the positive electrode filler include lithium iron phosphate, lithium cobaltate, lithium nickelate, lithium manganate, activated carbon, and carbon nanotube.
Examples of the negative electrode filler include lithium titanate, hard carbon, soft carbon, activated carbon, carbon nanotube, silicon, tin, and a compound containing germanium atoms. In particular, since a storage battery using a compound containing silicon, tin, and germanium atoms as a filler has a large volume expansion of the active material during charging, the use of the ionized aromatic resin of the present invention as a binder deteriorates the active material. It is preferable for reducing capacity deterioration during charging and discharging.

Examples of the compound containing silicon atom (silicon) include (1) silicon fine particles, (2) tin, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony, and chromium. And an alloy with silicon (3), boron, nitrogen, oxygen, or a compound of carbon and silicon, and those having the metal exemplified in (2). Examples of silicon alloys or compounds include SiB ₄ , SiB ₆ , Mg ₂ Si, Ni ₂ Si, TiSi ₂ , MoSi ₂ , CoSi ₂ , NiSi ₂ , CaSi ₂ , CrSi ₂ , Cu ₅ Si, FeSi ₂ , MnSi ₂ , NbSi ₂ , TaSi ₂ , VSi ₂ , WSi ₂ , ZnSi ₂ , SiC, Si ₃ N ₄ , Si ₂ N ₂ O, SiOv (0 <v ≦ 2), LiSiO, or the like.

Examples of the compound containing a tin atom include (1) an alloy of silicon, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony or chromium and tin, (2) Examples thereof include compounds of oxygen or carbon and tin, and those having the metal exemplified in (1). Examples of tin alloys or compounds include SnOw (0 <w ≦ 2), SnSiO ₃ , LiSnO, Mg ₂ Sn, and the like.
Examples of the compound containing a germanium atom include an alloy of silicon, tin, and germanium.

The median diameter (d50) in the particle size distribution of the filler is preferably in the range of 0.01 to 20 μm. Further, the surface of the filler may be treated with a silane coupling agent or the like.
Here, the median diameter can be measured using a laser diffraction / scattering particle size distribution measuring apparatus LA-920 manufactured by Horiba. Before the measurement, an appropriate amount of sample is added to the aqueous solution of sodium hexametaphosphate and dispersed with an ultrasonic cleaner for 10 minutes, and then the measurement is performed. This makes it possible to accurately measure the particle size distribution by agglomerating a sample in which the powder is agglomerated and suppressing the precipitation of powder having a large particle size.

  In the electrode slurry of the present invention, the content of the electrode binder composition excluding the solvent is preferably 1 part by mass or more with respect to 100 parts by mass of the filler from the viewpoint that the adhesiveness can be further improved. Part or more is more preferable, and 5 parts by mass or more is more preferable. Moreover, in order to reduce electrical resistance and increase the filling amount of the filler, the content of the electrode binder composition is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, relative to 100 parts by mass of the filler. 12 parts by mass or less is more preferable.

  In order to reduce the electric resistance of the secondary battery electrode or the capacitor electrode, the negative electrode paste of the present invention may contain conductive particles such as graphite, ketjen black, carbon nanotube, and acetylene black. These contents are preferably 0.1 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the negative electrode active material.

  The electrode binder composition and electrode slurry of the present invention can be obtained by mixing or kneading (a) a resin, (b) a basic compound, and, if necessary, a solvent and other additives. In the case of mixing, put each component in a glass flask or stainless steel container, etc., a method of stirring and dissolving with a mechanical stirrer, etc., a method of dissolving with ultrasonic waves, a method of stirring and dissolving with a planetary stirring deaerator, etc. Is mentioned. In the case of kneading, a method using a planetary mixer, three rolls, a ball mill, a homogenizer and the like can be mentioned. The conditions for mixing and kneading are not particularly limited.

  Further, the electrode binder composition or electrode slurry after mixing and kneading may be filtered with a pore size filter of 0.01 μm to 100 μm in order to remove foreign matters. Examples of the material for the filter include polypropylene (PP), polyethylene (PE), nylon (NY), polytetrafluoroethylene (PTFE), and polyethylene and nylon are preferable. Moreover, when a resin composition contains a filler or an organic pigment, it is preferable to use a filtration filter having a pore size larger than these particle sizes.

A laminated body can be made by applying the electrode binder composition or electrode slurry of the present invention to one or both sides of a substrate and drying.
As the base material, a conductive base material or an insulating base material having conductive wiring is used.

  Preferred examples of the conductive base material include, but are not limited to, copper, aluminum, stainless steel, nickel, gold, silver, alloys thereof, and carbon. In particular, copper, aluminum, stainless steel, nickel and alloys containing them are more preferable.

  As an insulating base material having conductive wiring, wiring using the metal used for the conductive base material or an alloy containing them is polyimide, polyamideimide, polyamide, polyester, acrylic resin, epoxy resin, phenol resin. Examples thereof include, but are not limited to, those formed on a silicone resin substrate.

Next, an example is given and demonstrated about the manufacturing method of the laminated body of this invention.
First, the slurry for an electrode of the present invention is applied on a substrate with a thickness of 1 to 500 μm. As the base material, when the laminate is used for a lithium ion battery negative electrode (hereinafter may be abbreviated as a negative electrode), a copper foil is generally used, and a lithium ion battery positive electrode (hereinafter abbreviated as a positive electrode). And aluminum double-layer capacitor positive and negative electrodes include aluminum foil, nickel foil, titanium foil and copper foil, and aluminum foil is generally used. For the application, methods such as screen printing, roll coating, and slit coating can be used.

  After applying the electrode slurry, heat treatment is performed at 100 to 250 ° C. for 10 minutes to 24 hours in order to remove the solvent. In order to suppress the mixing of moisture, it is preferable to heat in an inert gas such as nitrogen gas or in a vacuum.

Next, a lithium ion battery and an electric double layer capacitor using the positive electrode and the negative electrode of the present invention will be described.
About the positive electrode and negative electrode of this invention, what was laminated | stacked via the separator is put into exterior materials, such as a metal case, with an electrolyte solution, A secondary battery and an electric double layer capacitor can be obtained.

Examples of the separator include polyolefins such as polyethylene and polypropylene, microporous films such as cellulose, polyphenylene sulfide, aramid, and polyimide, and nonwoven fabrics.
In order to increase the heat resistance, the surface of the separator may be coated with ceramic or the like.

  The solvent used for the electrolytic solution serves as a medium through which ions involved in the electrochemical reaction of the battery can move. Preferred solvents include carbonate-based, ester-based, ether-based, ketone-based, alcohol-based and non-protonic solvents. Examples of the carbonate solvent include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), and ethyl methyl carbonate. (EMC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), and the like. Examples of the ester solvent include methyl acetate, ethyl acetate, n-propyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone, tecanolide, valerolactone, mevalonolactone, caprolactone, and the like. Examples of the ether solvent include dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, and tetrahydrofuran. Examples of the ketone solvent include cyclohexanone. Examples of the alcohol solvent include ethyl alcohol and isopropyl alcohol. Examples of the non-protonic solvent include tolyls, amides such as dimethylformamide, dioxolanes such as 1,3-dioxolane, and sulfolanes. Two or more of these solvents may be used, and the content ratio can be appropriately selected depending on the performance of the intended battery. For example, in the case of the carbonate-based solvent, it is preferable to use a combination of a cyclic carbonate and a chain carbonate in a volume ratio of 1: 1 to 1: 9, and the performance of the electrolytic solution can be improved.

  Examples of the electrolyte used for the electrolyte include lithium salts such as lithium hexafluorophosphate, lithium borofluoride, and lithium perchlorate, and ammonium salts such as tetraethylammonium tetrafluoroborate and triethylmethylammonium tetrafluoroborate.

  Examples are given below to describe the present invention in more detail, but the present invention is not limited by these examples. In addition, evaluation of the binder composition for electrodes in an Example was performed with the following method.

(1) Production of Negative Electrode A suitable amount of 80 parts by mass of the negative electrode active material obtained in Synthesis Example 3 below, 75 parts by mass of a binder composition for an electrode having a solid content concentration of 20% by weight, and 5 parts by mass of acetylene black as a conductive assistant. After being dissolved in the solvent (the same as that used when preparing the electrode binder composition) and stirring, a slurry-like paste was obtained. The obtained paste was applied onto an electrolytic copper foil using a doctor blade and dried at 110 ° C. for 30 minutes to obtain an electrode. Further, the coated portion of this electrode was punched out into a circle having a diameter of 16 mm and vacuum dried at 150 ° C. for 24 hours to produce a negative electrode.
However, only when a polyimide precursor solution (Composition 15) was used for the electrode binder composition, a process of adding heat treatment at 350 ° C. for 1 hour after drying at 110 ° C. for 30 minutes was added. .

(2) Electrode characteristic evaluation The long-term reliability as a battery was evaluated by the following method using the binder composition for electrodes of the present invention.
In measuring the charge / discharge characteristics, an HS cell (manufactured by Hosen Co., Ltd.) was used, and the lithium ion battery was assembled in a nitrogen atmosphere. In the cell, the produced negative electrode was punched into a circle with a diameter of 16 mm, the separator porous film (made by Hosen Co., Ltd.) was punched into a diameter of 24 mm, and an active material made of lithium cobalt oxide as the positive electrode Aluminum foil fired (made by Hosen Co., Ltd.) punched out to a diameter of 16 mm are stacked one after the other, and 1 mL of MIRET1 (Mitsui Chemicals Co., Ltd.) is injected and sealed, and then a lithium ion battery. Got.

  The lithium ion battery manufactured as described above is charged at a constant current of 6 mA until the battery voltage reaches 4.2 V, and further charged at a constant voltage of 4.2 V until reaching a total of 2 hours 30 minutes from the start of charging. It was. Thereafter, the charging was suspended for 30 minutes, and the battery was discharged at a constant current of 6 mA until the battery voltage became 2.7 V, and the first cycle was charged and discharged. Moreover, after that, charging / discharging was repeated 19 times under the same conditions, and the charging capacity and discharging capacity of each cycle were measured for a total of 20 cycles.

The capacity retention rate was calculated according to the following formula.
Capacity maintenance ratio (%) = (discharge capacity at 20th cycle / discharge capacity at 1st cycle) × 100
The initial charge / discharge efficiency was calculated according to the following equation.
Initial charge / discharge efficiency (%) = (discharge capacity at first cycle / charge capacity at first cycle) × 100

Synthesis Example 1: Synthesis of phenol resin (NV-01) Under a dry nitrogen stream, 57 g (0.6 mol) of metacresol, 38 g (0.4 mol) of paracresol, 75.5 g of a 37% by mass aqueous formaldehyde solution ( 0.93 mol of formaldehyde), 0.63 g (0.005 mol) of oxalic acid dihydrate, and 264 g of methyl isobutyl ketone were added, and the flask was immersed in an oil bath, and the reaction solution was refluxed for 4 hours. A condensation reaction was performed. Thereafter, the temperature of the oil bath is raised over 3 hours, and then the pressure in the flask is reduced to 30 to 50 mmHg to remove volatile components, and the dissolved resin is cooled to room temperature, and a phenol novolac. 85 g of polymer solid of resin (NV-01) was obtained.

Synthesis Example 2: Synthesis of polyhydroxystyrene (PHS-01) Into a 1 liter flask, 550 ml of tetrahydrofuran as a solvent and 4 × 10 ⁻⁴ mol of n-butyllithium as a polymerization initiator were charged, When 78 g of p-vinylphenoxydimethylphenylcarbinyldimethylsilane diluted with 50 ml of tetrahydrofuran was added at 78 ° C. and polymerized for 1 hour, the solution turned red. After confirming that the desired degree of polymerization was reached, methanol was added to the reaction solution to complete the polymerization reaction. The reaction mixture was poured into methanol to precipitate a polymer, and the precipitated polymer was washed and dried to obtain poly (p-vinylphenoxydimethylphenylcarbinyldimethylsilane).

  Next, 12 g of the resulting poly (p-vinylphenoxydimethylphenylcarbinyldimethylsilane) was dissolved in 250 ml of acetone, a small amount of hydrochloric acid was added, and the mixture was stirred at 60 ° C. for 6 hours. Was added to precipitate the polymer, and the precipitated polymer was washed and dried to obtain 8 g of a polymer of polyhydroxystyrene (PHS-01). The weight average molecular weight was 23,000.

Synthesis Example 3 Synthesis of Negative Electrode Active Material 50 g of natural graphite having a particle diameter of about 10 μm (Fuji Graphite Co., Ltd., CBF1), 60 g of nanosilicon powder (manufactured by Aldrich), and 10 g of carbon black (Mitsubishi Chemical Corporation) 3050) was mixed and dispersed well in a ball mill at a rotation speed of 600 rpm for 12 hours, and then vacuum-dried at 80 ° C. for 12 hours to obtain a Si—C-based negative electrode active material.

Synthesis Example 4 Synthesis of Polyimide Precursor Solution (PI-01) In a 1 liter flask, 123.3 g of N-methyl-2-pyrrolidone was added, 8.1 g of paraphenylenediamine, and 4,4′-diaminodiphenyl ether. 0 g was dissolved. This was charged with 28 g of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, stirred at 60 ° C. for 6 hours, cooled to room temperature and a polyimide precursor solution having a solid content concentration of 25% by weight ( PI-01) was obtained.

Compositions 1-15
An electrode binder composition having a solid content of 20% by weight was prepared according to the blending ratio shown in Table 1.

[Examples 1-13, Comparative Examples 1-2]
About composition 1-15, the evaluation result of a capacity | capacitance maintenance factor and initial stage charge / discharge efficiency is shown in Table 2.
In Table 1, PVDF represents polyvinylidene fluoride made by Kishida Chemical, CMC represents carboxymethyl cellulose # 2200 made by Daicel, and DMOM-PTBP, HMOM-W, and thermal acid generator N have the following structures.

Claims (18)

(A) A binder composition for an electrode comprising at least one resin selected from the following (a-1) to (a-3) and (b) a basic compound.
(A-1) Polyhydroxystyrene resin (a-2) Polystyrene resin having at least one selected from a carboxyl group and a sulfonic acid group in the side chain (a-3) Phenolic resin The binder composition for electrodes according to claim 1, wherein the (a) resin contains a polyhydroxystyrene-based resin having a structure represented by the following general formula (1).

(In the general formula (1), R ¹ and R ² represent an organic group or halogen having 1 to 5 carbon atoms. R ³ represents a monovalent organic group having 1 to 20 carbon atoms. R ⁴ , R ⁵ , R ⁶ represents a hydrogen atom or an organic group having 1 to 3 carbon atoms, a is an integer of 0 to 4, c is an integer of 0 to 5, b is an integer of 1 to 5, and a + b is an integer of 1 to 5. N ₁ is an integer of 10 to 10,000, n ₂ and n ₃ are integers of 0 to 10,000, and 0.2 ≦ n ₁ / (n ₁ + n ₂ + n ₃ ) ≦ 1.)   The electrode according to claim 1 or 2, wherein the (b) basic compound is contained in an amount of 5 to 100 mol% with respect to 100 mol% in total of the phenolic hydroxyl group, carboxyl group and sulfonic acid group in the (a) resin. Binder composition.   The binder composition for electrodes according to any one of claims 1 to 3, wherein the basic compound (b) contains at least one element selected from the group consisting of alkali metals and alkaline earth metals.   Furthermore, the binder composition for electrodes in any one of Claims 1-4 containing a thermal crosslinking agent. The binder composition for electrodes according to claim 5, wherein the thermal crosslinking agent contains a compound having a structure represented by the following general formula (2).

(In the general formula (2), R ¹³ , R ¹⁴ and R ¹⁵ may be the same or different and each represents hydrogen or a monovalent metal cation, and the total of R ¹³ , R ¹⁴ and R ¹⁵ is 100 mol%. 10 mol% or more is a monovalent metal cation, and R ¹⁶ and R ¹⁷ may be the same or different and each represents hydrogen or an organic group having 1 to 3 carbon atoms.) Furthermore, the binder composition for electrodes in any one of Claims 1-6 containing the cellulose compound which has a structure represented by following General formula (3).

(In General Formula (3), R ¹⁸ represents hydrogen or CH ₂ COOR ^19, and a plurality of R ¹⁸ may be the same or different. R ¹⁹ represents hydrogen, lithium, sodium, or potassium, and R ¹⁹ may be the same or different, and n ₇ represents an integer of 10 to 100,000.)   Furthermore, the binder composition for electrodes in any one of Claims 1-7 containing a solvent.   The electrode binder composition according to claim 8, wherein 80% by weight or more of the solvent is water.   The slurry containing the binder composition for electrodes in any one of Claims 1-9, and a filler.   The slurry according to claim 10, wherein the filler comprises a compound having at least one selected from the group consisting of carbon, manganese, cobalt, nickel, iron, silicon, titanium, tin, and germanium.   The slurry according to claim 10 or 11, wherein the filler contains at least one selected from the group consisting of silicon, silicon oxide, and lithium titanate.   The laminated body which has the layer formed from the slurry in any one of Claims 10-12 on the at least single side | surface of the insulating base material which has a conductive base material or conductive wiring.   The process of apply | coating the slurry in any one of Claims 10-12 to at least one surface of the insulating base material which has a conductive base material or a conductive wiring, and the process of drying the said coating film The manufacturing method of a laminated body containing this.   The electrode for secondary batteries which has the laminated body of Claim 13.   An electrode for an electric double layer capacitor, comprising the laminate according to claim 13.   A secondary battery comprising the secondary battery electrode according to claim 15.   An electric double layer capacitor comprising the electric double layer capacitor electrode according to claim 16.