JPWO2013154165A1 - Secondary battery electrode binder resin, secondary battery electrode composition, secondary battery electrode and secondary battery - Google Patents

Abstract

A secondary battery electrode binder resin comprising a monomer unit (а-1) having an alicyclic skeleton and a monomer unit (а-2) having a carboxyl group, the monomer unit having a carboxyl group By using a secondary battery electrode binder resin containing 5 to 55% by mass of (а-2) in the resin, the adhesion to the current collector is improved and the secondary battery electrode composition is excellent in electrolytic solution resistance. You can provide things. When this secondary battery electrode composition is used, it is possible to prevent the binder from eluting in the electrolytic solution or to absorb the electrolytic solution and swell greatly, thereby extending the life of the secondary battery.

Description

  The present invention relates to a secondary battery electrode binder resin having adhesiveness and excellent electrolyte solution resistance, a secondary battery electrode composition, a secondary battery electrode and a secondary battery obtained using the same.

In recent years, portable information terminals such as notebook personal computers, mobile phones, and PDAs have become widespread. Furthermore, hybrid cars and electric cars are being actively developed from the viewpoint of reducing environmental impact. Lithium secondary batteries having high energy density are widely used as power sources for these portable information terminals, hybrid vehicles, and electric vehicles.
Lithium-containing metal composite oxides are mainly used as positive electrode active materials for lithium secondary batteries. As the negative electrode active material, a carbon-based material having a multilayer structure capable of inserting lithium ions between layers (forming a lithium intercalation compound) and releasing is used. The electrode of the lithium secondary battery is a slurry prepared by kneading these active materials, binder and solvent, and this is applied to one or both sides of the current collector metal foil with a transfer roll or the like, and the solvent is removed by drying. Then, after forming the active material layer, it is produced by compression molding with a roll press machine or the like as necessary.

Conventionally, styrene / butadiene / rubber (hereinafter abbreviated as “SBR”) and polyvinylidene fluoride (hereinafter abbreviated as PVDF) have been used as secondary battery electrode binder resins. However, SBR and PVDF have poor adhesion to metal foils (aluminum foil, copper foil, etc.) that are current collectors. For this reason, in order to ensure sufficient adhesive force with the current collector of the active material layer, a large amount of binder resin must be blended with the active material. The binder resin contained in a large amount in the active material layer is a factor that hinders the increase in capacity of the lithium secondary battery by covering the active material and inhibiting the battery reaction of the active material or increasing the internal resistance of the lithium battery. It becomes.
Binder resins that can form an active material layer having high adhesiveness with a current collector include those disclosed in Patent Document 1 and Patent Document 2. When these binder resins are used, the adhesion between the active material layer and the current collector is improved as compared with SBR and PVDF.

JP-A-8-287915 JP 2011-134649 A

However, when the binder resins disclosed in Patent Document 1 and Patent Document 2 are immersed in an electrolytic solution, a part of the binder resin may be eluted or absorbed and may swell greatly. The material layer was peeled off from the current collector, which hindered extending the life of the secondary battery.
Therefore, the conventional secondary battery electrode binder resin is required to improve the property that the binder resin does not swell due to elution or absorption of the electrolyte in the electrolyte, that is, the resistance to electrolyte.
The subject of this invention is providing the secondary battery electrode binder resin excellent in electrolyte solution resistance while having adhesiveness with an electrical power collector.

The present invention provides the following.
1. A secondary battery electrode binder resin comprising a monomer unit (а-1) having an alicyclic skeleton and a monomer unit (а-2) having a carboxyl group, the monomer unit having a carboxyl group A secondary battery electrode binder resin containing 5 to 55% by mass of (а-2) in the resin.
2. 2. A secondary battery electrode composition comprising the secondary battery electrode binder resin described in 1 above. A secondary battery electrode using the secondary battery electrode composition according to 2 above.
4). A secondary battery comprising the secondary battery electrode as described in 3 above.

  By using the secondary battery electrode binder resin of the present invention, it is possible to provide a secondary battery electrode composition with improved adhesion to the current collector and excellent resistance to electrolyte. When a secondary battery is manufactured using an electrode formed with an active material layer using this secondary battery electrode composition, it is prevented that the binder elutes or absorbs the electrolytic solution and swells greatly in the electrolytic solution. Therefore, the lifetime of the secondary battery can be increased.

(Secondary battery electrode binder resin)
The secondary battery electrode binder resin of the present invention is a secondary battery electrode binder resin containing a monomer unit (а-1) having an alicyclic skeleton and a monomer unit (а-2) having a carboxyl group. And it is secondary battery electrode binder resin which contains 5-55 mass% of monomer units (а-2) which have a carboxyl group in resin.

In this invention, it is necessary to contain 5-55 mass% of monomer units (а-2) which have a carboxyl group in resin.
When the monomer unit (а-2) is less than 5% by mass in the resin, the electrolyte solution resistance of the binder resin is insufficient, and when it exceeds 55% by mass, the resin is solidified during the polymerization and stable production cannot be performed. .
The content of the monomer unit (а-2) in the resin is preferably 9% by mass or more from the viewpoint of resistance to electrolytic solution, and is preferably 50% by mass or less from the viewpoint that the binder resin can be stably produced.

  The monomer unit (а-2) is, for example, an acrylic carboxyl group-containing monomer such as acrylic acid and methacrylic acid, a croton carboxyl group-containing monomer such as crotonic acid, maleic acid and its anhydride. Maleic carboxyl group-containing monomer such as itaconic acid and its anhydride, itaconic carboxyl group-containing monomer, citraconic carboxyl group-containing monomer such as citraconic acid and its anhydride, fumaric acid , Mesaconic acid, cinnamic acid, succinic acid mono (2- (meth) acryloyloxyethyl), ω-carboxy-polycaprolactone mono (meth) acrylate, and the like. These may be used alone or in combination of two or more.

The monomer unit (а-2) is preferably a monobasic acid in that the binder resin can be produced stably.
Furthermore, at least one selected from the group consisting of acrylic acid and methacrylic acid is more preferable from the viewpoint of resistance to electrolytic solution.

  The monomer unit (а-1) is a monomer unit having an alicyclic skeleton. The “alicyclic skeleton” means a cyclic aliphatic hydrocarbon group. It may be monocyclic or polycyclic. Moreover, the carbon number which comprises a ring is about 3-50, More preferably, it is about 3-20, More preferably, it is 5-10.

The monomer unit (а-1) is, for example, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, adamantyl (meth) acrylate, tricyclodecanyl (meth) acrylate, dicyclopentadienyl (meth) acrylate, It is a unit obtained by copolymerizing dicyclopentanyl (meth) acrylate and the like and derivatives having a substituent on the alicyclic ring of these compounds. These may be used alone or in combination of two or more.
Moreover, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, and dicyclopentanyl (meth) acrylate are preferable in terms of excellent electrolytic solution resistance.

  The monomer unit (а-1) is preferably contained in the resin in an amount of 30% by mass or more, more preferably 35% by mass or more, and further preferably 40% by mass or more from the viewpoint of improving the electrolytic solution resistance. The monomer unit (а-1) is preferably 75% by mass or less, and more preferably 65% by mass or less from the viewpoint of improving adhesiveness.

  Furthermore, in the present invention, monomer units other than the monomer units (а-1) and (а-2) may be included. Examples of monomer units other than monomer units (а-1) and (а-2) include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and the like. Alkyl (meth) acrylates; aromatic vinyl monomers such as styrene and α-methylstyrene; vinyl cyanide monomer units such as acrylonitrile, methacrylonitrile, α-cyanoacrylate, dicyanovinylidene and fumaronitrile; ethoxyethyl ( (Meth) acrylate, methoxyethyl (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, methoxytriethylene glycol (meth) acrylate, phenoxydiethylene glycol (meth) acrylate, methoxypolyethylene oxide mono (meth) acrylate , Lauroxy polyethylene oxide mono (meth) acrylate, stearoxy polyethylene oxide mono (meth) acrylate, allyloxy polyethylene oxide mono (meth) acrylate, nonyl phenoxy polyethylene oxide mono (meth) acrylate, nonyl phenoxy polypropylene oxide mono (meth) acrylate , Polyalkylene oxide group-containing (meth) acrylates such as octoxy (polyethylene oxide-polypropylene oxide) mono (meth) acrylate and nonylphenoxy (polyethylene oxide-propylene oxide) mono (meth) acrylate; hydroxyethyl (meth) acrylate, hydroxy Butyl (meth) acrylate, hydroxypropyl (meth) acrylate, 1,2-dihydroxyethyl ( (Meth) acrylate, 1,2-dihydroxypropyl (meth) acrylate, 1,2-dihydroxybutyl (meth) acrylate, 1,2-dihydroxy5-ethylhexyl (meth) acrylate, 1,2,3-trihydroxypropyl (meth) ) Acrylate, 1,2,3-trihydroxybutyl (meth) acrylate, 1,1-dihydroxyethyl (meth) acrylate, 1,1-dihydroxypropyl (meth) acrylate, 1,1-dihydroxybutyl (meth) acrylate, 1,1,2-trihydroxypropyl (meth) acrylate, 1,1,2-trihydroxybutyl (meth) acrylate, glycidyl (meth) acrylate, hydroxy polyethylene oxide mono (meth) acrylate, hydroxy polypropylene oxide (Meth) acrylate, hydroxy (polyethylene oxide-polypropylene oxide) mono (meth) acrylate, hydroxy (polyethylene oxide-propylene oxide) mono (meth) acrylate, hydroxy (polyethylene oxide-polytetramethylene oxide) mono (meth) acrylate, hydroxy Hydroxy content such as (polyethylene oxide-tetramethylene oxide) mono (meth) acrylate, hydroxy (polypropylene oxide-polytetramethylene oxide) mono (meth) acrylate, hydroxy (polypropylene oxide-polytetramethylene oxide) mono (meth) acrylate ( (Meth) acrylate; N-dimethylaminoethyl (meth) acrylate, N-diethylaminoethyl (meth) acrylate Amino group-containing (meth) acrylates such as: (meth) acrylamide, (meth) acrylamide diacetone acrylamide, N-methylol (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N-ethoxymethyl (meth) acrylamide, N -(Meth) acrylamide derivatives such as butoxymethyl (meth) acrylamide; 2- (meth) acryloyloxyethyl acid phosphate, 2- (meth) acryloyloxyethyl acid phosphate monoethanolamine salt, diphenyl ((meth) acryloyloxyethyl) ) Phosphate, (Meth) acryloyloxypropyl acid phosphate, 3-chloro-2-acid phosphooxypropyl (meth) acrylate, acid phosphooxypolyoxyethyl Phosphoric acid group-containing monomers such as lenglycol mono (meth) acrylate and acid phosphooxypolyoxypropylene glycol (meth) acrylate; ethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, di ( 1,3-butylene glycol (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, hydroxypivalic acid Neopentyl glycol di (meth) acrylic acid ester, di (meth) acrylic acid polypropylene glycol, di (meth) acrylic acid polytetramethylene glycol, trimethylol propane tri (meth) acrylic acid ester, ethoxylated trimethylol proppant (Meth) acrylic acid ester, propoxylated trimethylolpropane tri (meth) acrylic acid ester, glycerin tri (meth) acrylic acid ester, ethoxylated glycerin tri (meth) acrylic acid ester, divinylbenzene, divinylnaphthalene, divinyl ether It is obtained by polymerizing polyfunctional monomers such as vinyl acetate and vinyl propionate. These (a-3) components may be used individually by 1 type, and may use 2 or more types together.

  Among these, alkyl (meth) acrylate is preferable from the viewpoint of easy copolymerization with the components (a-1) and (a-2), and the alkyl group has about 1 to 10 carbon atoms. Alkyl (meth) acrylates are preferred. Moreover, the adhesiveness with the electrical power collector of an active material layer can be improved by using a suitable quantity of a phosphoric acid group containing monomer. Moreover, the electrolytic solution resistance of the binder can be improved by using an appropriate amount of a functional monomer such as ethylene glycol di (meth) acrylate or polyethylene glycol di (meth) acrylate.

The weight average molecular weight (Mw) measured by the gel permeation chromatography (GPC) method of the secondary battery electrode binder resin of the present invention is preferably 5,000 or more. If Mw is 5,000 or more, it is possible to provide adhesion between the active material layer obtained by using the binder resin and the current collector, and also to impart resistance to the electrolyte to the binder resin. Preferably, the weight average molecular weight (Mw) measured by GPC is 30,000 to 5,000,000.
GPC can be determined as a polystyrene-equivalent molecular weight using a solvent such as tetrahydrofuran as an eluent.

The volume average particle diameter of the secondary battery electrode binder resin of the present invention is preferably 1 nm to 10 μm. When the volume average particle diameter of the secondary battery electrode binder resin is within the above range, the secondary battery electrode binder resin works well as a binder, and the battery resistance is lowered.
Here, the volume average particle diameter is a value measured using a light scattering photometer. In addition, the volume average particle diameter in this invention refers to the primary particle diameter at the time of manufacture, and is different from the secondary particle diameter which is the particle diameter when granulation is performed thereafter.

The secondary battery electrode binder resin can be produced by polymerizing a monomer mixture containing a monomer having an alicyclic skeleton and a monomer having a carboxyl group by a known method.
Examples of the polymerization method include known methods such as bulk polymerization, suspension polymerization, emulsion polymerization, and solution polymerization. Of these, emulsion polymerization is preferred in terms of ease of polymerization and ease of post-treatment such as recovery and purification.

  In the present invention, in order to set each monomer unit in the resin to a predetermined amount, the amount of the charged monomer may be set to a predetermined amount. For example, a monomer unit having a carboxyl group ( In order to make а-2) 5 to 55% by mass in the resin, the amount of the monomer having a carboxyl group should be included in the total monomer in the amount of 5 to 55% by mass during the preparation. It ’s fine.

  Examples of the emulsifier used in the emulsion polymerization include an anionic emulsifier (sodium dodecylbenzenesulfonate, sodium lauryl sulfonate, sodium lauryl sulfate, etc.), an anionic emulsifier containing a polyoxyethylene group, a nonionic emulsifier (polyoxy Ethylene nonylphenyl ether, polyoxyethylene lauryl ether, etc.) and a reactive emulsifier having a vinyl polymerizable double bond in the molecule can be used, but there is no particular limitation.

  Examples of the polymerization initiator used in the emulsion polymerization include peroxides such as benzoyl peroxide, cumene hydroperoxide, and hydrogen peroxide; azo compounds such as azobisisobutyronitrile; ammonium persulfate and potassium persulfate. Persulfuric acid compounds such as perchloric acid compounds, perboric acid compounds, or redox initiators composed of a combination of peroxides and reducing sulfoxy compounds can be used, but there is no particular limitation.

  In the case of emulsion polymerization, a chain transfer agent may be used. As the chain transfer agent, known ones such as mercaptans such as n-dodecyl mercaptan, tert-dodecyl mercaptan, n-octyl mercaptan, n-tetradecyl mercaptan, n-hexyl mercaptan, and α-methylstyrene dimer can be used. However, there is no particular limitation. Although the quantity of a chain transfer agent can be suitably determined according to the objective and kind, For example, it can add in the range of 0.01-30 mass parts with respect to 100 mass parts of monomers.

  Moreover, when performing emulsion polymerization, after dripping and superposing | polymerizing 1 or more types of a monomer, the method of dripping and superposing | polymerizing 1 or more types of other monomers, and the inside of the container of a superposition | polymerization apparatus Use a method (seed polymerization method) or the like to prepare an emulsion containing seed particles, and then drop the copolymer material into the emulsion containing seed particles little by little, and heat and polymerize at a predetermined temperature. I can do it.

(Secondary battery electrode composition)
The secondary battery electrode binder resin of the present invention can be used as a secondary battery electrode composition.
The secondary battery electrode composition of the present invention includes an active material. The active material is not particularly limited as long as it can reversibly insert and release lithium ions by charging and discharging the lithium secondary battery.
For example, examples of the positive electrode active material include lithium and a lithium-containing metal composite oxide containing one or more metals selected from iron, cobalt, nickel, and manganese. Examples of the lithium-containing metal composite oxide include lithium cobaltate, lithium manganate, and lithium nickelate. These positive electrode active materials may be used alone or in combination of two or more.
On the other hand, examples of the negative electrode active material include carbon materials such as graphite, amorphous carbon, carbon fiber, coke, and activated carbon. A composite of such a carbon material and a metal such as silicon, tin, silver, or an oxide thereof can also be used. These negative electrode active materials may be used alone or in combination of two or more.

  The secondary battery electrode composition of the present invention is obtained by drying a slurry obtained by kneading the secondary battery electrode binder resin of the present invention, the active material and a solvent.

  There is no restriction | limiting in particular as a solvent used for the said slurry, What is necessary is just a solvent which can melt | dissolve or disperse | distribute a secondary battery electrode binder resin and an active material uniformly. For example, water; hydrocarbons such as n-dodecane, decahydronaphthalene and tetralin; alcohols such as 2-ethyl-1-hexanol and 1-nonanol; ketones such as holon, acetophenone and isophorone; benzyl acetate, isopentyl butyrate , [Gamma] -butyrolactone, esters such as methyl lactate, ethyl lactate and butyl lactate; amines such as o-toluidine, m-toluidine and p-toluidine; N-methyl-2-pyrrolidone, N, N-dimethylacetamide and dimethyl Amides such as formamide; and sulfoxides and sulfones such as dimethyl sulfoxide and sulfolane. These solvents may be used alone or in combination of two or more. Of these, water is preferred because of its low environmental impact.

When water is used as a solvent, 0.01 to 200 parts by mass of a water-soluble thickener may be used as an additive as needed with respect to 100 parts by mass of the active material for the purpose of adjusting the slurry viscosity. . Examples of the water-soluble thickener include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, polyacrylic acid (salt), oxidized starch, phosphorylated starch, and casein. These water-soluble thickeners may be used alone or in combination of two or more.
When water is used as a solvent, an emulsion obtained by emulsion polymerization can be used as it is as a binder resin containing a solvent.

  The slurry is preferably used at a viscosity of 50 to 50,000 mPa · s, more preferably 100 to 10,000 mPa · s. The slurry having the above viscosity range can be obtained by appropriately adjusting the amount of the solvent and the addition amount of the water-soluble thickener.

  The amount of the secondary battery electrode binder resin of the present invention contained in the slurry is preferably 0.1 to 10 parts by mass, more preferably 0.2 to 7 parts by mass, particularly preferably 100 parts by mass of the active material. Is 0.5-5 parts by mass. If the amount of the binder resin relative to the active material is too small, the active material may be easily dropped from the electrode having the active material layer obtained using the slurry. On the other hand, if the amount of the binder resin relative to the active material is too large, the active material contained in the active material layer may be covered with the binder resin, thereby inhibiting the battery reaction or increasing the internal resistance.

  In addition to the binder, the active material, and the solvent, the slurry may contain a conductive material such as conductive carbon such as acetylene black, ketjen black, carbon black, graphite, vapor-grown carbon fiber, and carbon nanotube. it can. By using these, the electrical contact between the electrode active materials can be improved, and the discharge rate characteristics can be improved when used in a non-aqueous electrolyte secondary battery. The amount of these conductive materials used is preferably 20 parts by mass or less with respect to 100 parts by mass of the electrode active material.

  Further, a compound having two or more functional groups capable of reacting with a carboxyl group can be added to the slurry as a crosslinking agent. Examples of the functional group capable of reacting with a carboxyl group include an epoxy group, a carbodiimide group, an oxazoline group, and an isocyanate group. By adding these cross-linking agents, the adhesion between the active material layer obtained by using the secondary battery electrode binder resin of the present invention and the current collector can be improved, and the binder resin electrolyte-resistant solution Can be improved. The amount of these crosslinking agents added is preferably in the range of 0.01 to 30 parts by mass with respect to 100 parts by mass of the binder resin. These crosslinking agents may be used alone or in combination of two or more.

  Examples of compounds having two or more epoxy groups that can be used as a crosslinking agent include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol polyglycidyl ether, diglycerol diglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl. Ether, sorbitol polyglycidyl ether, pentaerythritol, diglycidyl ether, trimethylolpropane polyglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, glycidyl (meth) acrylate copolymer resin, bisphenol A, novolak type A phenol resin, an ortho cresol novolak type phenol resin, etc. can be mentioned.

  Examples of the compound having two or more carbodiimide groups that can be used as a crosslinking agent include 1,5-naphthalenecarbodiimide, 4,4′-diphenylmethanecarbodiimide, 4,4′-diphenyldimethylmethanecarbodiimide, 1,3-phenylenecarbodiimide, 1 , 4-phenylene diisocyanate, 2,4-tolylene carbodiimide, 2,6-tolylene carbodiimide, a mixture of 2,4-tolylene carbodiimide and 2,6-tolylene carbodiimide, hexamethylene carbodiimide, cyclohexane-1,4- Carbodiimide, xylylene carbodiimide, isophorone carbodiimide, isophorone carbodiimide, dicyclohexylmethane-4,4'-carbodiimide, methylcyclohexanecarbodiimide, tetramethylxylylene carbodiimi , 2,6-diisopropylphenyl-carbonitrile di Imi, 1,3,5-triisopropylbenzene-2,4-carbodiimide and the like.

  Examples of the compound having two or more oxazoline groups that can be used as a crosslinking agent include 2,2′-o-phenylenebis (2-oxazoline), 2,2′-m-phenylenebis (2-oxazoline), and 2,2. '-P-phenylenebis (2-oxazoline), 2,2'-p-phenylenebis (4-methyl-2-oxazoline), 2,2'-m-phenylenebis (4-methyl-2-oxazoline), 2,2′-p-phenylenebis (4,4′-dimethyl-2-oxazoline), 2,2′-m-phenylenebis (4,4′-dimethyl-2-oxazoline), 2,2′-ethylene Bis (2-oxazoline), 2,2′-tetramethylene bis (2-oxazoline), 2,2′-hexamethylene bis (2-oxazoline), 2,2′-octamethylene bis (2-oxa Phosphorus), 2,2'-ethylenebis (4-methyl-2-oxazoline), or 2,2'- diphenylenebis (2-oxazoline) and the like.

  The compounds having two or more isocyanate groups that can be used as a crosslinking agent include ethylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, heptamethylene diisocyanate, octamethylene diisocyanate, decamethylene diisocyanate, dodecamethylene. Linear polymethylene diisocyanates such as diisocyanate and tetradecamethylene diisocyanate; methyltetramethylene diisocyanate, dimethyltetramethylene diisocyanate, trimethyltetramethylene diisocyanate, methylhexamethylene diisocyanate, dimethylhexamethylene diisocyanate, trimethylhexamethylene diisocyanate, Branched alkylene diisocyanates such as luoctamethylene diisocyanate, dimethyloctamethylene diisocyanate, trimethyloctamethylene diisocyanate; 1,2-diisocyanatocyclopentane, 1,3-diisocyanatocyclopentane, 1,2-diisocyanatocyclohexane 1,3-diisocyanatocyclohexane, 1,4-diisocyanatocyclohexane, 1,2-bis (isocyanatomethyl) cyclohexane, 1,3-bis (isocyanatomethyl) cyclohexane, 1,4-bis (isocyanate) Natomethyl) cyclohexane, dicyclohexylmethane-2,2′-diisocyanate, dicyclohexylmethane-2,4′-diisocyanate, dicyclohexylmethane-3,3′-diisocyanate, dicyclohexyl 4,4'-diisocyanate, cycloalkane ring containing diisocyanates such like, and the like.

(Secondary battery electrode)
The secondary battery electrode of the present invention comprises a secondary battery electrode composition and a current collector.
The current collector is not particularly limited as long as it is made of a conductive material, and examples thereof include those made of metal such as iron, copper, aluminum, nickel, and stainless steel. Although the shape is not particularly limited, it is preferable to use a sheet having a thickness of about 0.001 to 0.5 mm.

The secondary battery electrode of the present invention is obtained by applying the slurry to a current collector and drying it.
The slurry may be applied on one side or both sides of the current collector.
The method for applying the slurry to the current collector is not particularly limited. For example, doctor blade method, dipping method, reverse roll (transfer roll) method, direct roll method, gravure method, extrusion method, dipping, brush coating And the like. The amount to be applied is not particularly limited. For example, the amount of the active material layer formed after drying the slurry is 0.005 to 1 mm, preferably 0.01 to 0.5 mm. can do.

  The method for drying the slurry is not particularly limited, and examples include air drying, hot air drying, infrared heating, a far infrared heater, vacuum drying, and the like. The drying temperature may be appropriately selected according to the boiling point of the solvent contained in the slurry, but is usually around 150 ° C. When a crosslinking agent is added, heat treatment may be performed as necessary.

  Furthermore, the density of the active material of the electrode may be increased by compressing the secondary battery electrode after drying with a press machine or the like. Examples of the pressing method include a die press and a roll press, and are not particularly limited.

(Secondary battery)
The secondary battery of the present invention includes the secondary battery electrode. Specifically, it has the above-described secondary battery electrode, an electrolytic solution, and a separator. In addition, the secondary battery of this invention should just use said secondary battery electrode in at least one of a positive electrode or a negative electrode.

The electrolyte solution for the secondary battery may be a commonly used one, and a battery that functions as a battery may be selected according to the type of the negative electrode active material and the positive electrode active material. As the electrolyte contained in the electrolytic solution, for example, any conventionally known lithium salt can be used, and examples thereof include LiClO ₄ , LiBF ₆ , and LiPF ₆ . The solvent of the electrolytic solution is not particularly limited as long as it is usually used. Mainly carbonates such as propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate; γ-butyl Lactones such as lactones; ethers such as trimethoxymethane, 1,2-dimethoxyethane, diethyl ether, 2-ethoxyethane, tetrahydrofuran and 2-methyltetrahydrofuran. These solvents may be used alone or as a mixed solvent of two or more.

  The separator is made of a porous polymer film such as a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer. The produced porous polymer film can be used alone or in layers. In addition, a normal porous nonwoven fabric, for example, a nonwoven fabric made of high melting point glass fiber, polyethylene terephthalate fiber or the like can be used, but is not limited thereto.

  There is no restriction | limiting in particular about the manufacturing method of the secondary battery of the said invention. As a manufacturing method, for example, a positive electrode and a negative electrode are overlapped via a separator, wound in a spiral according to the shape of the battery, folded, put into a battery container, injected with an electrolyte, and sealed. The method is mentioned. The shape of the battery may be any of a coin shape, a cylindrical shape, a square shape, a flat shape, and the like.

Hereinafter, although an example and a comparative example explain the present invention, the present invention is not limited to this. In the following Examples and Comparative Examples, “part” means “part by mass”, and “%” means “% by mass”.
Evaluation methods in the following examples and comparative examples are as follows.

<Volume average particle diameter>
The volume average particle diameter of the secondary battery electrode binder resin was measured using a light scattering photometer FPAR-1000 type (manufactured by Otsuka Electronics Co., Ltd.).

<Adhesiveness>
Cellophane tape was affixed to the surface of the active material layer of the electrode produced by the method described later. After peeling the adhered cellophane tape at a constant speed, the state of the active material layer on the surface of the current collector was observed and evaluated according to the following criteria.
A: The active material layer bound on the current collector is hardly peeled off and the current collector surface is not visible.
○: The active material layer bound on the current collector is slightly peeled off, but the current collector surface is not visible.
Δ: A part of the active material layer bound on the current collector is peeled off, and a part of the current collector surface is seen.
X: The active material layer bound on the current collector is almost peeled off, and the current collector surface is entirely seen.

<Electrolytic resistance>
The obtained secondary battery electrode binder resin was dried to form a dry film. The obtained dried film was immersed in a mixed solvent of ethylene carbonate / dimethyl carbonate (mass ratio 1: 2) at 50 ° C. for 24 hours, and the swelling ratio was measured according to the following (formula-1) to determine the resistance to electrolyte. Examined. It can be evaluated that the smaller the swelling ratio, the higher the electrolytic solution resistance. In addition, when adding a crosslinking agent, after adding a crosslinking agent and making it dry, the dry film heat-processed for 30 minutes at 150 degreeC was used.

(Formula-1)
Swell ratio (%) = (resin weight after immersion) / (resin weight before immersion) × 100
◎: Less than 280% ○: 280% or more and less than 330% Δ: 330% or more and less than 380% ×: 380% or more

<Weight average molecular weight>
The weight average molecular weight (Mw) of the copolymer was calculated in terms of polystyrene by the GPC method. Specifically, a sample was dissolved in THF to prepare a 0.3% THF solution as a resin component, which was filtered through a 0.5 μm membrane filter, and the filtrate was used for weight average by the GPC method under the following conditions. The molecular weight was measured.

(Measurement condition)
Apparatus: Tosoh HPLC-8120GPC
Column: Tosoh TSKgel SuperHM-H (6.0 mmID × 15 cmL) connected in series.
Eluent: THF
Flow rate: 0.6 mL / min Temperature: 40 ° C
Detector: Differential refractometer Injection amount: 20 μL

<Examples 1-12, 17-19, Comparative Examples 1-3>
In a container of a polymerization apparatus capable of heating and cooling, 250 parts of water (solvent), 2.0 parts of sodium dialkylsulfosuccinate (manufactured by Kao Corporation, “Perex OTP”), 0.3 part of ammonium persulfate (polymerization) Initiator) and the monomer mixture shown in Tables 1 and 3 were charged and heated at 70 ° C. for 7 hours in a nitrogen atmosphere with stirring at a rotation speed of 200 rpm for polymerization to obtain a secondary battery electrode binder resin. It was.

  To 7.0 parts of the obtained secondary battery electrode binder resin (2% in terms of binder resin solid content with respect to the active material), 100 parts of 1% aqueous solution of CMC (manufactured by Aldric) and active material (ITO Graphite Industries Co., Ltd.) ) Manufactured graphite AGB-5) 100 parts was added and kneaded to obtain a slurry containing a secondary battery electrode binder resin. The obtained slurry was applied on a copper foil having a thickness of 18 μm so that the thickness of the negative electrode active material layer after drying was 50 μm, and then dried at 110 ° C. for 10 minutes to obtain a secondary battery electrode. The evaluation results are shown in Tables 1 and 3.

<Examples 13 to 16>
In a container of a polymerization apparatus that can be heated and cooled, 250 parts of water (solvent), 2.0 parts of sodium dialkylsulfosuccinate (manufactured by Kao Corporation, “Perex OTP”) and 0.3 part of ammonium persulfate (Polymerization initiator) and the monomer mixture shown in Table 2 were charged, and the mixture was heated and polymerized at 70 ° C. for 7 hours in a nitrogen atmosphere while stirring at a rotation speed of 200 rpm to obtain a secondary battery electrode binder resin. It was. Table 2 shows the volume average particle diameter of the obtained secondary battery electrode binder resin. In 7.0 parts of the obtained secondary battery electrode binder resin (2% in terms of binder resin solid content with respect to the active material), a crosslinking agent shown in Table 2 and 100 parts of CMC (manufactured by Aldric) 1% aqueous solution and 100 parts of an active material (artificial graphite AGB-5 manufactured by Ito Graphite Industries Co., Ltd.) was added and kneaded to obtain a slurry containing a secondary battery electrode binder resin. The obtained slurry was applied on a copper foil having a thickness of 18 μm so that the thickness of the negative electrode active material layer after drying was 50 μm, and then dried at 110 ° C. for 10 minutes, and then continuously under vacuum conditions at 150 ° C. for 30 minutes. A secondary battery electrode was obtained by heat treatment. The evaluation results are shown in Table 2.

In addition, the symbol in Tables 1-3 shows the following materials.
CHMA: cyclohexyl methacrylate IBXA: isobornyl acrylate MAA: methacrylic acid AA: acrylic acid nBA: normal butyl acrylate AN: acrylonitrile EDMA: ethylene glycol dimethacrylate PP1000: polypropylene glycol monomethacrylate (Blenmer PP1000; manufactured by NOF Corporation)
EX-810: Ethylene glycol diglycidyl ether (Denacol EX810; manufactured by Nagase Chemtech)
V-02: Aqueous solution of polyvalent carbodiimide (Carbodilite V-02, manufactured by Nisshinbo Chemical Co., Ltd.)
WS700: Aqueous solution of oxazoline group-containing polymer (Epocross WS700, manufactured by Nippon Shokubai Co., Ltd.)
DNW6000: Modified polyisocyanate (Bernock DNW6000, manufactured by DIC Corporation)
Moreover, each numerical value of the monomer in Table 1-Table 3, a crosslinking agent, and a chain transfer agent represents each mass part when a monomer sum is 100 mass parts.

In Comparative Example 1, since the monomer unit (а-1) having an alicyclic skeleton was not included, the electrolytic solution resistance and adhesiveness were insufficient.
In Comparative Example 2, since the number of monomer units (а-2) having a carboxyl group was small, the resistance to electrolytic solution was insufficient.
In Comparative Example 3, since there were many monomer units (а-2) having a carboxyl group, the resin solidified during the polymerization, and the intended resin could not be obtained.
On the other hand, when the resin of the present invention was used, a binder resin having excellent electrolytic solution resistance and good adhesion could be obtained (Examples 1 to 19).

Claims (15)

A monomer unit (а-1) having an alicyclic skeleton;
A secondary battery electrode binder resin comprising a monomer unit (а-2) having a carboxyl group,
A secondary battery electrode binder resin containing 5 to 55% by mass of a monomer unit (а-2) having a carboxyl group in the resin.   The secondary battery electrode binder resin according to claim 1, wherein the monomer unit (а-1) is contained in an amount of 30 to 70% by mass in the resin.   The secondary battery electrode binder resin according to claim 1, wherein the monomer unit (а-1) is contained in an amount of 35 to 65% by mass in the resin.   The secondary battery electrode binder resin according to claim 1, wherein the monomer unit (а-2) is contained in the resin in an amount of 9 to 50% by mass.   The secondary battery electrode binder resin according to claim 1 or 2, wherein the number of carbon atoms constituting the ring of the monomer unit (а-1) is 5 to 10.   The monomer unit (а-1) is at least one selected from the group consisting of cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, and dicyclopentanyl (meth) acrylate. Secondary battery electrode binder resin.   The secondary battery electrode binder resin according to any one of claims 1 to 4, wherein the monomer unit (а-2) is a monobasic acid.   The secondary battery electrode binder resin according to any one of claims 1 to 4, wherein the monomer unit (а-2) is at least one selected from the group consisting of acrylic acid and methacrylic acid.   The secondary battery electrode binder resin according to any one of claims 1 to 4, comprising a monomer unit (а-3) derived from an alkyl (meth) acrylate.   The secondary battery electrode binder resin according to any one of claims 1 to 4, which has a weight average molecular weight of 30,000 to 5,000,000 as determined by gel permeation chromatography (GPC).   The secondary battery electrode composition containing the secondary battery electrode binder resin in any one of Claims 1-4.   The secondary battery electrode composition according to claim 11, comprising a compound having two or more functional groups capable of reacting with a carboxyl group in the molecule.   The secondary battery electrode composition according to claim 12, wherein the functional group capable of reacting with the carboxyl group of the compound is at least one selected from the group consisting of an epoxy group, a carbodiimide group, an oxazoline group, and an isocyanate group.   A secondary battery electrode using the secondary battery electrode composition according to claim 11.   A secondary battery comprising the secondary battery electrode according to claim 14.