JP2018181486A - Electrode binder resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode binder resin composition which has good resistance against an electrolyte solution, which is high in binding property and slurry stability, and which enables the dramatic enhancement in battery discharge rate characteristic and cycle characteristics.SOLUTION: An electrode binder resin comprises a polymer containing (a) a monomer unit originating from an ethylenic unsaturated carboxylic acid ester compound having a structure given by the formula I (where -X- is a straight-chain or branched alkylene group with C3-12 or a cycloalkylene group with C4-12; and Rand Rindependently represent a hydrogen atom or a methyl group), and (b) a monomer unit originating from an ethylenic unsaturated sulfonic acid compound. The polymer has a crosslinking density of 1×10mol/cc or more and less than 1×10mol/cc.SELECTED DRAWING: None

Description

  The present invention relates to a binder resin composition for an electrode, an electrode material slurry using the binder resin composition for an electrode, an electrode using the same, a secondary battery, and an electric double layer capacitor.

  In recent years, capacitors such as a lithium ion secondary battery, a nickel hydrogen secondary battery, a secondary battery such as a nickel cadmium secondary battery, an electric double layer capacitor, and the like, which can be repeatedly used by charging, are used in electronic devices. .

  These secondary batteries and capacitors are generally configured to include an electrolyte, an electrode, a separator, and an electrolyte. The electrode is manufactured by coating and drying an electrode material slurry, in which an electrode active material is dispersed in a solvent in which a binder (binder) is dissolved, on an electrode current collector, to form a mixture layer.

  Polyvinylidene fluoride (hereinafter referred to as "PVDF") is conventionally and industrially used as a binder for lithium ion secondary battery electrodes, but has not been able to sufficiently cope with the recent level of demand for higher performance of batteries. .

  In addition, when using PVDF as a binder, for example, as disclosed in Patent Document 1 etc., amides such as N-methylpyrrolidone (hereinafter, NMP) as a solvent for laminating a mixture layer, Nitrogen-containing organic solvents such as ureas are used. However, nitrogen-containing organic solvents such as NMP must be recovered because solvent vapor generated during drying is an environmental problem if released to the atmosphere as it is.

  Therefore, it has been proposed to use an aqueous binder as the binder. For example, Patent Document 2 discloses a paste in which a carbon material as a negative electrode active material is mixed with an aqueous emulsion of an acrylic copolymer as a binder and a mixed hydrate of carboxymethyl cellulose and these are dispersed in water as a solvent. Negative electrode mix is shown.

  However, conventional aqueous binders are mainly diverted to the negative electrode plate, and inadequate to the positive electrode plate, particularly with respect to the dispersion of the coating slurry in the electrode plate manufacturing process, or the performance of the obtained battery is not sufficient There was a problem of

  Further, in particular, in recent years, with the demand for higher performance of the battery, the change of the active material has been advanced, and there is a reality that high performance is also required for the binder.

  In patent document 3, it is supposed that an active material and a conductive support agent are strongly bound by using the binder which has an intraparticle crosslinking structure using a 3- to 5-functional (meth) acrylate crosslinking monomer.

  In Patent Document 4, a (meth) acrylate crosslinking monomer is used to prevent swelling / dissolution in a non-aqueous electrolytic solution, peeling of the active material from the current collector of the electrode, or deterioration of the bonding between the active materials, It is said that the shortage of electrolyte in the department will be improved. Then, it is supposed that a secondary battery having high capacity and excellent charge / discharge cycle characteristics such as high rate charge / discharge cycle, low temperature charge / discharge cycle, etc. can be obtained because swelling / dissolution by the electrolytic solution becomes small.

  Patent Document 5 discloses a binder composition for an electrode, which comprises polymer particles containing an ethylenically unsaturated carboxylic acid ester compound and an ethylenically unsaturated sulfonic acid compound in a predetermined mass ratio.

Japanese Patent Application Publication No. 2004-134365 JP 2000-294230 A JP, 2014-160638, A JP 2001-256980 A International Publication No. 2013/069558

  Furthermore, when PVDF is used as a binder, there is a problem such as insufficient bonding between the current collector and the electrode film and between the active materials, and there is a problem in the cycle characteristics of the battery due to peeling and falling of the mixture. Since the viscosity stability over time of the electrode material slurry, the binding property to the current collector, and the electrolytic solution resistance of the binder affect the cycle characteristics and the like, improvement is required.

  The inventors of the present invention noticed that the binder resin composition for an electrode may be significantly dissolved or swollen in an electrolyte used in a secondary battery.

  Moreover, in the binder composition for electrodes of the said patent document 5, the swelling degree was too high, and the discharge rate characteristic and cycling characteristics of the battery which were obtained were inadequate.

  Accordingly, an object of the present invention is to provide a binder resin composition for an electrode having good resistance to an electrolytic solution, and having excellent storage stability and coating smoothness of an electrode material slurry, and An object of the present invention is to provide a binder resin composition for an electrode which is excellent in discharge rate characteristics and cycle characteristics of a battery.

  As a result of repeated studies to achieve the above object, the present inventors are polymers (polymers) containing a structural unit derived from a monomer (monomer) described later, and the crosslink density of the polymer is specified. It has been found that if the polymer in the range is used as a binder resin for an electrode, the above problems are solved, and the present invention has been completed.

  Therefore, the present invention includes the following (1):

（式中、−Ｘ−は、炭素数３〜１２の直鎖もしくは分岐のアルキレン基、または炭素数４〜１２のシクロアルキレン基であり、Ｒ¹及びＲ²はそれぞれ独立に水素原子又はメチル基である）
に由来する単量体単位と、
（ｂ）エチレン性不飽和スルホン酸化合物
に由来する単量体単位とを、
含有するポリマーを含み、
上記ポリマーの架橋密度が、１×１０^-4ｍｏｌ／ｃｃ以上１×１０^-3ｍｏｌ／ｃｃ未満である、電極用バインダー樹脂組成物。 (1)
(A) Ethylenically unsaturated carboxylic acid ester compound having a structure of the following formula I

(Wherein, -X- is a linear or branched alkylene group having 3 to 12 carbon atoms or a cycloalkylene group having 4 to 12 carbon atoms, and R ¹ and R ² are each independently a hydrogen atom or a methyl group Is)
Monomer units derived from
(B) a monomer unit derived from an ethylenically unsaturated sulfonic acid compound,
Containing polymers,
A binder resin composition for an electrode, wherein a crosslinking density of the polymer is 1 × 10 ⁻⁴ mol / cc or more and 1 × 10 ⁻³ mol / cc or less.

(2)
The above-mentioned polymer is further contained as component (c),
(C1) a monomer unit derived from an ethylenically unsaturated carboxylic acid ester compound having a hydroxyl group at an alcohol-derived site in an ester structure,
(C2) The compound according to (1), which contains any one or more of monomer units derived from an ethylenically unsaturated carboxylic acid ester compound having an alkyl group having 8 or more carbon atoms in an alcohol-derived site in an ester structure Binder resin composition for electrodes.

(3)
The binder resin composition for electrodes as described in (2) whose content of the monomer unit of (c1) component is 1-10 mass% in the said polymer.

(4)
The polymer described in (2) or (3), wherein the proportion of the monomer units of the (c2) component is 10 to 98.9% by mass in the total of the (a) component and the (c) component. Binder resin composition for electrodes.

(5)
For the electrode according to any one of (1) to (4), the content of monomer units of the component (a) is 0.1 to 10% by mass with respect to the total mass of the polymer Binder resin composition.

(6)
In the above polymer, the mass ratio of the content of the monomer unit of the component (a) and the component (c) when present to the content of the monomer unit of the component (b) {(a) + (c)}: (B) is in the range of 98-91: 2-9,
In the above polymer, the ratio of the total amount of the monomer units of the component (a) and the monomer units of the component (b) and the monomer units of the component (c) is 70% by mass or more. The binder resin composition for electrodes as described in any one of (1)-(5).

(7)
Further, the above-mentioned polymer is used as the component (c)
(1) to (1) containing 1 to 30% by mass of a monomer unit derived from an ethylenically unsaturated carboxylic acid ester compound having an alkyl group of 1 to 7 carbon atoms at a site derived from alcohol in the ester structure (c3) 6) The binder resin composition for electrodes as described in any one of 6).

(8)
Further, the above-mentioned polymer is
(D) The binder resin composition for electrodes as described in any one of (1)-(7) which contains 0.1-10 mass% of monomer units derived from an ethylenically unsaturated carboxylic acid compound.

(9)
The binder resin composition for electrodes as described in any one of (1)-(8) whose binder resin for electrodes is a form of the polymer emulsion which the particle | grains of a polymer disperse | distribute in an aqueous solvent.

(10)
The electrode material slurry containing the binder resin composition for electrodes as described in any one of (1)-(9), and an active material.

(11)
(10) An electrode containing the application dry layer of the electrode material slurry as described in (10).

(12)
The secondary battery containing the electrode as described in (11).

(13)
An electric double layer capacitor comprising the electrode according to (11).

  According to the present invention, it is possible to provide a binder resin composition for an electrode having good resistance to an electrolytic solution, high binding property and high slurry stability, and capable of dramatically improving the discharge rate characteristics and cycle characteristics of the battery. It is.

  Hereinafter, embodiments of the present invention will be described in detail. The present invention is not limited to the embodiments described below.

  In the present specification, "(meth) acrylic" means that both "acrylic and methacrylic" are included, and "(meth) allyl" includes both "allyl and methallyl". means.

  In the present specification, the symbol “to” (tilde) indicating a numerical range is meant to include the lower limit value and the upper limit value unless otherwise specified.

  In the present specification, for the sake of easy understanding, a symbol indicating a monomer unit (component) contained in a polymer may also be diverted to a raw material compound.

ここで式中、−Ｘ−は、炭素数３〜１２、より好ましくは炭素数６〜１０の直鎖もしくは分岐のアルキレン基、または炭素数４〜１２のシクロアルキレン基であり、またＲ¹及びＲ²はそれぞれ独立に水素原子又はメチル基である。 [Binder resin composition for electrode]
The binder resin composition for electrodes according to the embodiment of the present invention (hereinafter sometimes referred to simply as “binder resin”) is an ethylenically unsaturated carboxylic acid represented by the structural formula of the following formula I as component (a) It contains a monomer unit derived from an acid ester compound.

Here, in the formula, -X- is a linear or branched alkylene group having 3 to 12 carbon atoms, more preferably 6 to 10 carbon atoms, or a cycloalkylene group having 4 to 12 carbon atoms, and R ¹ and Each R ² is independently a hydrogen atom or a methyl group.

  Furthermore, the said binder resin also contains the monomer unit derived from an ethylenically unsaturated sulfonic acid compound as (b) component.

In one embodiment, the binder resin is a monomer unit derived from an ethylenically unsaturated carboxylic acid ester compound having a hydroxyl group at a site derived from alcohol in (c1) ester structure as component (c).
(C2) a monomer unit derived from an ethylenically unsaturated carboxylic acid ester compound having an alkyl group having 8 or more carbon atoms in an alcohol-derived site in an ester structure (c3) an alcohol-derived site in an ester structure It may contain any one or more of monomer units derived from the ethylenically unsaturated carboxylic acid ester compound having an alkyl group of 7.

  In one embodiment, the binder resin may further contain, as the component (d), a monomer unit derived from an ethylenically unsaturated carboxylic acid compound.

The above polymer has a crosslink density represented by the following formula:
Crosslink density (mol / cc) = G '/ RT
(Wherein, G ′ represents a storage elastic modulus (dyn / cm ² ), R represents a gas constant (8.31 × 10 ⁷ [(dyn · cm) / (mol · K)]), and T is an absolute Represents temperature (K))
Is in the range of 1 × 10 ⁻⁴ mol / cc to 1 × 10 ⁻³ mol / cc. Details of the crosslinking density will be described later.

Crosslink density
In a preferred embodiment, the ethylenically unsaturated carboxylic acid ester compound represented by the component (a) and the formula I functions as a crosslinking agent, and by adjusting the crosslink density in a predetermined range, in a small amount Even if it is present, the binder resin can exhibit high binding power.

The number of cross-linking molecules present per unit volume in the polymer which is the binder resin is also referred to as cross-linking density (unit: mol / cc). The crosslink density is a dynamic shear storage modulus G ′ (unit: dyn / cm ² ) which is an equilibrium region in a rubbery region observed by temperature dependence measurement of a dynamic shear storage modulus (frequency 1 Hz) of the binder resin. ) And the temperature T (unit: K) at which the equilibrium region is reached, according to the following equation:

Crosslink density (mol / cc) = G '/ RT
R in the formula is a gas constant (8.31 × 10 ⁷ [(dyn · cm) / (mol · K)]).

The value of the crosslink density can be adjusted by appropriately setting the type and amount of the crosslinking component and the polymerization conditions. In particular, the type and amount of the crosslinking component have a great influence on the value of the crosslinking density. When the value of the crosslink density is 1 × 10 ⁻⁴ mol / cc or more and less than 1 × 10 ⁻³ mol / cc, it becomes possible to obtain a binder resin which is hardly soluble in an electrolytic solution and hardly swells. Preferably, the crosslink density is in the range of 2 × 10 ^-4 mol / cc to 1 × 10 ^-3 mol / cc, more preferably 4 × 10 ^-4 mol / cc to 1 × 10 ^-3 mol / cc. It can be in the range of 5 × 10 ⁻⁴ mol / cc or more and 1 × 10 ⁻³ mol / cc or more. When the crosslinking density is low, the cycle characteristics and the discharge rate characteristics may be inferior.

  By setting the crosslink density of the binder resin in the above-mentioned range, high binding strength can be exhibited even if a small amount is used. In addition, since the binder resin is basically an insulator, the internal resistance can be reduced, for example, when applied to a lithium ion secondary battery, by setting the amount of the binder resin used to a small amount. It can improve.

[Dynamic shear storage modulus]
Specifically, the temperature dependence of the dynamic shear storage elastic modulus is a dynamic shear storage elastic modulus G ′ of the binder resin from the temperature of the glassy region of the resin to the temperature of the rubbery region (ie, It can be measured while changing the temperature from the temperature below the glass transition temperature of the resin to the temperature above the glass transition temperature. At this time, in the above temperature range, the equilibrium region (plateau) of high dynamic shear storage modulus continues to the glass transition point in the glassy region, and the dynamic shear storage modulus decreases from the vicinity of the glass transition point, and the rubbery region In the low dynamic shear storage modulus equilibrium region. The dynamic shear storage elastic modulus of the flat area in this rubbery area is the G '(dyn / cm ² ). In the present specification, G ′ is measured at 100 ° C. because around 100 ° C. is included in the equilibrium region regardless of the type of polymer used.

[Measurement of dynamic shear storage modulus]
The dynamic shear storage elastic modulus of the binder resin is, for example, drying a liquid binder composition containing the binder resin to prepare a film of the binder resin which is solid content, and using the binder resin film, the dynamic viscoelasticity is obtained. It is possible to measure by a measuring device.

  More specifically, the dynamic shear storage modulus of the binder resin can be measured by the following procedure.

  As a binder resin, for example, a polymer emulsion containing polymer particles is prepared, and this polymer emulsion is dried in a room temperature (5 to 35 ° C.) environment.

  Then, it is dried in a constant temperature bath at a high temperature (for example, a temperature in the range of 60 to 140 ° C. (for example, 105 ° C.)) for several dozen minutes to several hours (for example, 30 minutes to 2 hours (for example, 1 hour)) A resin film of 0.4 to 4 mm is produced.

  Subsequently, the film of the produced binder resin is cut | judged, a film piece is obtained, and it measures with a dynamic-viscoelasticity measuring apparatus with this film piece.

[Glass transition point]
The glass transition point of the binder resin is preferably as low as possible within the range in which the rigidity of the particles obtained in the electrode production process or the like can be maintained. A binder resin having a glass transition temperature in this range causes little change in large resin characteristics in a practical use temperature range, and leads to improvement of low temperature characteristics and durability when applied to a lithium ion secondary battery. In addition, a glass transition point can be adjusted to a desired range with the kind of monomer raw material which comprises binder resin, and its usage amount.

[Measurement of glass transition point]
In the present specification, the glass transition point (Tg) is measured as follows.

  The binder resin is poured into a mold and dried at 23 ° C. for 5 days to prepare a film having a thickness of 0.3 to 0.5 mm. Using the produced film as a sample, differential scanning calorimetry (DSC) measurement is performed according to JIS K 7121: 1987. And let the intersection of the tangent of the baseline in a DSC curve, and the tangent of the steep descent | fall position of the heat absorption area | region by glass transition be Tg.

[(A) Ethylenically Unsaturated Carboxylic Acid Ester Compound Having the Structure of Formula I]
An ethylenically unsaturated carboxylic acid ester compound having a structure of Formula I is composed of a moiety derived from an ethylenically unsaturated carboxylic acid compound and a moiety derived from an alcohol, and an ethylenically unsaturated carboxylic acid and (mono or di) It can be obtained from alcohol and a known method.

  The "alcohol-derived moiety" is based on that a carboxylic acid ester (R-COO-R ') is typically generated by the reaction of a carboxylic acid (R-COOH) with an alcohol (R'-OH). This refers to the site derived from this alcohol.

  Examples of the structure (portion) represented by X of the formula I of the component (a) include butylene glycol, pentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol and tricyclodecanedimethanol May be mentioned, but ethylene glycol and triethylene glycol etc. are not included.

  As the component (a), for example, 1,3-butylene glycol diacrylate, 1,6-hexanediol diacrylate, tricyclodecane glycol diacrylate, 3-methyl-1,5-pentanediol diacrylate, neopentyl glycol diacrylate Acrylate, 1,9-nonanediol diacrylate, 2-methyl-1,8-octanediol diacrylate, 1,10-decanediol diacrylate. Among these, 1,3-butylene glycol diacrylate, 1,6-hexanediol diacrylate, and tricyclodecane glycol diacrylate are preferable, and 1,6-hexanediol diacrylate is more preferable. The components (a) may be used in combination of two or more.

  The component (a) is used, for example, in an amount of 0.1 to 10% by mass, preferably 3 to 10% by mass, more preferably 3 to 8% by mass, based on the total mass of the monomer raw material used. be able to. As a result, the content of structural units derived from monomers relative to the mass of the polymer can be in the same range. By incorporating in this manner, the coatability of the electrode material slurry becomes very good, and it is possible to obtain a secondary battery electrode having good resistance to electrolyte solution swelling and further excellent in heat resistance. This contributes to obtaining a secondary battery with good battery output characteristics.

[(B) Ethylenically unsaturated sulfonic acid compound]
(B) As the ethylenically unsaturated sulfonic acid compound, for example, vinyl sulfonic acid, p-styrene sulfonic acid, (meth) allyl sulfonic acid, polyoxyethylene-1-allyloxymethyl alkyl sulfonic acid ester, polyoxyalkylene alkenyl Ether sulfonic acid ester, polyoxyethylene allyloxy methyl alkoxyethyl sulfonic acid ester, alkyl allyl sulfosuccinic acid, polyoxyalkylene (meth) acrylate sulfonic acid ester, etc. 1 type, or 2 or more types of thing, salts thereof, etc. Can be mentioned. Examples of this salt include alkali metal salts (Na, K etc.), alkaline earth metal salts and ammonium salts.

  Among the above-mentioned examples, p-styrenesulfonic acid, polyoxyethylene-1- (allyloxymethyl) alkylsulfonic acid ester, polyoxyalkylene alkenyl ether sulfonic acid ester, polyoxyethylene allyloxymethyl alkoxyethyl sulfonic acid ester, and those Salts thereof are preferred, and polyoxyethylene-1- (allyloxymethyl) alkylsulfonic acid esters and salts thereof are preferred. The components (b) may be used in combination of two or more.

  The content of the component (b) is, for example, 1 to 10% by mass, preferably 1 to 9% by mass, and more preferably 1 to 7% by mass, based on the total mass of the monomer raw material used it can. As a result, the content of structural units derived from monomers relative to the mass of the polymer can be in the same range. In a preferred embodiment, monomer units of components (a) and (b) and components (c) (including components (c1), (c2) and (c3)) which are optional inclusions described later The mass ratio of the content {(a) + (c)}: (b) can be in the range of 98-91: 2-9. At this time, the ratio of the total amount of the monomer units of the component (a) and the monomer units of the component (b) and the monomer units of the component (c) is 70% of the total mass of the polymer % Or more is preferable, more preferably 80% by mass or more, still more preferably 90% by mass or more, and still more preferably 95% by mass or more. By setting it as such content, binder resin can be used conveniently as a slurry for secondary battery electrodes.

[(C1) Ethylenically unsaturated carboxylic acid ester compound having a hydroxyl group at an alcohol-derived site in the ester structure]
In the component (c1), the alkyl group is preferably linear or branched, and more preferably linear. It is preferable that it is 1-8, and, as for carbon number of an alkyl group, it is more preferable that it is 1-3. Further, the number of hydroxyl groups is not particularly limited, but is preferably 1 to 2. Preferably, the ethylenically unsaturated carboxylic acid moiety is acrylic acid.

  As the component (c1), 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, (meth) Examples thereof include hydroxycyclohexyl acrylate and the like. Among these, 2-hydroxyethyl methacrylate is more preferable. The component (c1) may be used in combination of two or more.

  The component (c1) may be used, for example, in an amount of 1 to 10% by mass, preferably 2 to 8% by mass, and more preferably 3 to 7% by mass, based on the total mass of the monomer raw material used. it can. As a result, the content of structural units derived from monomers relative to the mass of the polymer can be in the same range.

[(C2) Ethylenically unsaturated carboxylic acid ester compound having an alkyl group having 8 or more carbon atoms at an alcohol-derived site in an ester structure]
As the component (c2), components corresponding to the component (c1) are excluded.

  The carbon number of the alkyl group of the alcohol-derived portion in the ester structure of the component (c2) is 8 or more, preferably 8 to 18, 8 to 12, 8 to 10, and the like. The alkyl group may be linear or branched, preferably branched.

  Examples of the component (c2) include 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, t-octyl (meth) acrylate, n-dodecyl (meth) acrylate, n-octadecyl acrylate Nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate and the like. Among these, 2-ethylhexyl methacrylate is preferable, and 2-ethylhexyl acrylate is more preferable. The component (c2) may be used in combination of two or more.

  The component (c2) is 10 to 98.9% by mass, preferably 60 to 90.9% by mass, more preferably 70 to 85.9% by mass based on the total of the components (a) and (c) used. % Can be used. The proportion of monomer units in the polymer obtained from the component (c2) can also be in the same range.

[(C3) Ethylenically unsaturated carboxylic acid ester compound having an alkyl group of 1 to 7 carbon atoms at an alcohol-derived site in an ester structure]
As the component (c3), components corresponding to the component (c1) are excluded.

  The alkyl group can be linear or branched, preferably linear. Carbon number of the alkyl group of the site | part derived from the alcohol in ester structure is 1-7, Preferably it can be set to 1-3. The ethylenically unsaturated carboxylic acid moiety may be (meth) acrylic acid, preferably methacrylic acid.

  Examples of the component (c3) include (meth) acrylic esters having an alkyl group of 1 to 7 carbon atoms at the alcohol-derived site in the ester structure, and examples include methyl (meth) acrylate and (meth) acrylic acid Mention may be made of ethyl, propyl (meth) acrylate, butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate and heptyl (meth) acrylate. Preferably, methyl methacrylate can be mentioned. The component (c3) may be used in combination of two or more.

  The component (c3) can be used, for example, in an amount of 1 to 30% by mass, preferably 1 to 10% by mass, based on the total mass of the monomer raw material used. As a result, the content of the monomer-derived structural unit relative to the mass of the polymer can be in the same range.

[(D) Ethylenically unsaturated carboxylic acid]
Examples of the component (d) include (meth) acrylic acid. The component (d) is, for example, 0.1 to 10% by mass, preferably 0.1 to 1.5% by mass, and more preferably 0.2 to 1.% by mass based on the total mass of the monomer raw material used. 0% by weight can be used. As a result, the content of structural units derived from monomers relative to the mass of the polymer can be in the same range. By incorporating the component (d) at such a low content, the electrode material slurry of the binder resin is excellent in storage stability, and when the slurry is applied, the smoothness of the coating film is excellent. can do.

[Combination of Preferred Raw Material Monomers]
In a preferred embodiment, as a monomer that is a raw material of a polymer that is a binder resin,
(A) an ethylenically unsaturated carboxylic acid ester compound represented by the formula I
(B) Ethylenically unsaturated sulfonic acid compounds,
(C1) an ethylenically unsaturated carboxylic acid ester compound having a hydroxyl group at an alcohol-derived site in an ester structure,
(C2) an ethylenically unsaturated carboxylic acid ester compound having an alkyl group having a carbon number of 8 or more at an alcohol-derived site in an ester structure,
(C3) an ethylenically unsaturated carboxylic acid ester compound having an alkyl group of 1 to 7 carbon atoms at an alcohol-derived site in an ester structure, and (d) an ethylenically unsaturated carboxylic acid,
Can be used in combination. In this case, it is considered that the component (a) and the other monomer crosslink.

[Form of binder resin]
The binder resin has a function of binding an active material in an electrode formed of an electrode material slurry containing the binder resin and an active material. In a preferred embodiment, the binder resin can be in the form of polymer particles dispersed in a dispersing medium. In a preferred embodiment, the binder resin can be in the form of a polymer emulsion in which polymer particles which are binder resin are dispersed in an aqueous solvent. That is, this polymer emulsion is also a composition containing a binder resin.

[Polymer emulsion]
The polymer which is the binder resin of the present invention can, in a preferred embodiment, be in the form of a polymer emulsion in which the polymer particles are dispersed in an aqueous solvent. In the form of a polymer emulsion, the content (resin content) of polymer particles (binder resin) in the polymer emulsion is not particularly limited as long as it can be dispersed in a solvent, for example, 0.2 to 80% by mass It can be 0.5 to 70% by mass and 10 to 60% by mass.

  The polymer emulsion preferably has a pH of 5 to 10, preferably 5 to 9 in view of the corrosiveness of the collector metal and the dispersion stability of the active material. It may be prepared by adding a basic aqueous solution in which ammonia, alkali metal hydroxide and the like are dissolved. Examples of the alkali metal hydroxide include sodium hydroxide and potassium hydroxide.

  The polymer emulsion may also contain an additive such as a polymer other than the above-described polymer particles to be dispersed, a viscosity modifier, and a fluidizing agent.

[Aqueous solvent]
An aqueous solvent can be suitably used as a dispersion medium for the polymer emulsion. As an aqueous solvent, for example, water can be mentioned. However, within the dispersible range, examples of the dispersion medium include alcohols such as ethyl alcohol, isopropyl alcohol and n-propyl alcohol, ketones such as diacetone alcohol and γ-butyrolactone, ethers, and glycol ethers These can also be used as a mixture with water as a main dispersion medium.

[Polymerization of Monomer]
The above monomers can be polymerized to obtain the polymer according to the present invention. In a preferred embodiment, the polymerized monomers can be obtained as a polymer emulsion. The polymer emulsion can be produced by a known method such as an emulsion polymerization method, a suspension polymerization method, or an emulsion dispersion method. In order to polymerize each said monomer and to obtain the polymer emulsion which concerns on this invention, additives, such as a polymerization initiator, a molecular weight modifier, and an emulsifier, can be used.

Emulsion polymerization
Among polymerization methods, emulsion polymerization can be suitably used for producing the polymer emulsion according to the present invention. In particular, a polymer emulsion having good properties can be obtained by emulsion polymerization by an emulsion dropping method in which a monomer raw material, water, and part of an emulsifier are mixed and dispersed in advance and added during polymerization.

[Polymerization initiator]
Examples of polymerization initiators include organics such as lauroyl peroxide, diisopropyl peroxydicarbonate, di-2-ethylhexylperoxydicarbonate, t-butylperoxypivalate and 3,3,5-trimethylhexanoyl peroxide. Peroxides, azo compounds such as α, α'-azobisisobutyronitrile, ammonium persulfate, potassium persulfate and the like can be mentioned. A polymerization initiator may be used individually by 1 type, and may be used in combination of 2 or more types.

[Electrode material slurry]
If the binder resin for electrodes of this invention and the binder composition for electrodes are used, the electrode material slurry excellent in storage stability and excellent in the smoothness of the coating film to a collector can be obtained. Furthermore, by using this electrode material slurry, it is possible to obtain an electrode which is particularly excellent in the adhesion (binding ability) between the current collector and the active material and the pencil hardness of the film. By using this electrode for a secondary battery or a capacitor, it is possible to obtain a secondary battery or a capacitor excellent in cycle characteristics and discharge rate characteristics.

  The electrode material slurry may further contain additives and the like. The electrode material slurry can be suitably used for formation of electrodes in secondary batteries such as lithium ion secondary batteries and nickel hydrogen secondary batteries, and electric double layer capacitors. An electrode material slurry can be used for an electrode as a coating dry layer.

[Active material in electrode material slurry]
As the active material contained in the electrode material slurry, those used in ordinary secondary batteries and capacitors can be used. As the active material, a positive electrode active material and a negative electrode active material are used.

As the positive electrode active material, as a general _{formula, A a M m Z z O} o N n F f (A is an alkali metal element; M is a transition metal element (Fe, Mn, V, Ti , Mo, W, Zn) or The complex; Z is a nonmetallic element (P, S, Se, As, Si, Ge, B); O is an oxygen element; N is a nitrogen element; F is a fluorine element; a, m, z, n, f ≧ The compound represented by 0; o> 0) is mentioned.

As the positive electrode active material of a lithium ion secondary battery, for example, lithium metal composite oxide composed mainly of Li _x MetO ₂ and the like. In this case, Met is one or more transition metals, and is, for example, one or more selected from cobalt, nickel, manganese and iron, and x is usually 0.05 ≦ x ≦ 1. It is in the range of 0. Specific examples of such lithium metal composite oxides include LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , LiFeO _{2 and the} like.

Also, for example, olivine lithium compounds such as olivine lithium phosphate compounds represented by olivine lithium iron phosphate (LiFePO ₄ ) and LiMetPO ₄ (Met = V, Fe, Ni, Mn), TiS ₂ , MoS ₂ Well-known positive electrode active materials such as metal sulfides and metal oxides not containing lithium such as NbS ₂ and V ₂ O ₅ , composite metals such as NbSe _{2, and the} like. Among these positive electrode active materials, LiFePO ₄ is preferable.

The negative electrode active material of the lithium ion secondary battery is selected from lithium metal, an alloy of Li and a low melting point metal such as Pb, Bi and Sn, a lithium alloy such as a Li-Al alloy, a carbonaceous material, etc. 1 There may be mentioned species or two or more species. As the carbonaceous negative electrode active material, any material that can occlude and release lithium ions that are main components of battery operation can be used, and carbon-based compounds such as graphitizable carbon, non-graphitizable carbon, polyacene and polyacetylene, pyrene, Aromatic hydrocarbon compounds containing an acene structure such as perylene are preferably used. Various carbonaceous materials can be used. Further, lithium titanate represented by Li _x Ti _y O _z or the like, and metal oxide compounds such as SiO _x and SnO _x can also be used.

  As a positive electrode active material of a nickel hydrogen secondary battery, nickel hydroxide etc. are mentioned, for example. As a negative electrode active material of a nickel hydrogen secondary battery, a hydrogen storage alloy is mentioned, for example. Examples of the positive electrode active material and the negative electrode active material of the electric double layer capacitor include activated carbon and the like.

[Content of binder resin in electrode material slurry]
The content of the binder resin composition for electrodes in the electrode material slurry can be, for example, 0.1 to 10 parts by mass with respect to 100 parts by mass of the active material. When the amount of the binder resin is 0.1 parts by mass or more, an active material such as LiFePO ₄ can be easily dispersed uniformly in the coating liquid, and the strength of the dried film after coating can easily be obtained. When the amount of the binder resin is 10 parts by mass or less, the decrease in the amount of active material in the positive electrode can be suppressed, so that the decrease in the charge capacity can be suppressed.

[Conductive agent in electrode material slurry]
The electrode material slurry may optionally contain a conductive additive and the like. Examples of the conductive additive include carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black and thermal black, carbon nanotubes, graphite powder, and various types of graphite. One or two or more of these conductive assistants may be used.

[Composite material in electrode material slurry]
The electrode material slurry may contain a composite material in which a plurality of conductive aids and active materials are connected in order to improve the conductivity and conductivity of the conductive aid and the active material. This composite material is, for example, in the case of a lithium ion secondary battery electrode material slurry, a carbon black composite in which fibrous carbon and carbon black are connected, and a composite of olivine-type lithium iron phosphate carbon coated on this composite. An integrated composite material etc. are mentioned. The carbon black composite in which fibrous carbon and carbon black are connected can be obtained, for example, by firing a mixture of fibrous carbon and carbon black. Alternatively, a mixture of the carbon black composite and a positive electrode active material such as olivine-type lithium iron phosphate can be fired to form a composite.

  A carbon black composite and a composite material in which a carbon-coated lithium olivine type iron phosphate is further integrated with the carbon black composite are generally used as a water-based electrode material having good properties generally due to problems of dispersibility and the like. It was difficult to obtain a slurry. However, a good electrode material slurry can be obtained by using the binder composition.

[Additives in electrode material slurry]
The electrode material slurry of the present embodiment may contain a viscosity modifier, a fluidizing agent, and the like, as necessary. Examples of such additives include water-soluble polymers such as polyvinyl alcohol, carboxymethyl cellulose, methyl cellulose and polymethacrylic acid.

[electrode]
The present invention also resides in an electrode manufactured using the above electrode material slurry. The electrode can be obtained by applying an electrode material slurry on a current collector, drying it, and laminating it as an electrode mixture layer. The positive electrode is manufactured by the electrode material slurry containing the positive electrode active material, and the negative electrode is manufactured by the electrode material slurry containing the negative electrode active material. The electrode can be suitably used for the production of secondary batteries such as lithium ion secondary batteries and nickel hydrogen secondary batteries, and electric double layer capacitors.

[Current collector]
A well-known material can be used as a material of a positive electrode collector, for example, aluminum can be used. For the negative electrode current collector, known materials can be used, and for example, copper or aluminum can be used. The shape of the current collector is not particularly limited, but foil-like, net-like, expanded metal, etc. can be used. The shape of the current collector is preferably a mesh-like or expanded metal having a large void area from the viewpoint of facilitating holding of the electrolytic solution after bonding, and a thickness of about 0.001 to 0.03 mm is preferable.

[Production of electrode]
A general method can be used for the method of applying the electrode material slurry. For example, reverse roll method, direct roll method, blade method, knife method, extrusion method, curtain method, gravure method, bar method, dip method and squeeze method can be mentioned. Among them, the blade method (comma roll or die cut), the knife method and the extrusion method are preferable. Under the present circumstances, the surface state of a favorable application layer can be obtained by selecting the said application method according to the solution physical property of a binder, and dryness. The application may be performed on one side or both sides, and in the case of both sides, one side may be sequentially or both sides simultaneously. The application may be continuous, intermittent or stripe. The application thickness, length, and width of the electrode material slurry may be appropriately determined in accordance with the size of the battery. For example, the coating thickness of the electrode material slurry, that is, the thickness of the mixture layer can be in the range of 10 μm to 500 μm.

  The electrode material slurry can be dried by a commonly employed method. In particular, it is preferable to use hot air, vacuum, infrared, far infrared, electron beam and low temperature air singly or in combination. In the present embodiment, by using the electrode material slurry prepared with water as the solvent, drying can be performed at a temperature of about 50 to 130 ° C., and energy for drying can be reduced.

The electrodes can be pressed as needed. As the pressing method, a commonly employed method can be used, but in particular, a die pressing method and a calendar pressing method (cold or hot roll) are preferable. The pressing pressure is not particularly limited, but is preferably 0.2 to 3 t / cm ² .

[Secondary battery and capacitor]
The present invention is also in a secondary battery and a capacitor manufactured using the above electrode. Examples of secondary batteries include lithium ion secondary batteries and nickel hydrogen secondary batteries. Examples of capacitors include electric double layer capacitors. Among these, the electrode is preferably used for a lithium ion secondary battery.

  In addition, the secondary battery and the capacitor of the present embodiment are configured to include the electrodes (a positive electrode and a negative electrode), a separator, and an electrolyte solution (hereinafter sometimes referred to simply as “electrolyte”). It is suitable. In addition, you may combine the positive electrode or negative electrode which concerns on the said embodiment with electrodes other than the said embodiment.

[separator]
As the separator, any electrically insulating porous film, mesh, non-woven fabric, etc. may be used as long as it has sufficient strength. In particular, it is preferable to use one which is low in resistance to ion migration of the electrolyte and excellent in solution retention. The material is not particularly limited, but examples thereof include inorganic fibers such as glass fibers or organic fibers, polyethylene, polypropylene, polyester, synthetic resins such as polytetrafluoroethylene and polyflon, or layered composites of these. Polyethylene, polypropylene or a layered composite film thereof is desirable from the viewpoint of adhesion and safety.

[Electrolyte solution]
As an electrolytic solution in the case of a lithium ion secondary battery, one configured to have a non-aqueous solvent such as an organic solvent containing a supporting electrolyte of lithium salt (hereinafter sometimes referred to simply as “electrolyte”) is preferable It is. The electrolyte in the electrolyte solution in this case, any known lithium salt can be _{used, LiClO 4, LiBF 4, LiBF} 6, LiPF 6, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF 6, LiSbF 6, LiB 10 _{Cl 10, LiAlCl 4, LiCl,} LiBr, LiI, LiB (C 2 H 5) 4, LiCF 3 SO 3, LiCH 3 SO 3, LiCF 3 SO 3, LiC 4 F 9 SO 3, LiN (CF 3 SO 2) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , lithium lower fatty acid carboxylate and the like, but not particularly limited.

  As an electrolyte solution in the case of a nickel hydrogen battery, the aqueous solution of electrolytes, such as sodium hydroxide, lithium hydroxide, potassium hydroxide, is mentioned. The electrolytic solution in the case of the electric double layer capacitor is configured to have a non-aqueous solvent such as an organic solvent containing an electrolyte such as ammonium salt and sulfonium salt. As the organic solvent in this case, one or more mixed solvents of carbonates, alcohols, nitriles, amides, ethers and the like can be used.

  Examples of the organic solvent which dissolves the electrolyte in the case of a lithium ion secondary battery include carbonates, lactones such as γ-butyrolactone, ethers, sulfoxides such as dimethyl sulfoxide, oxolanes, nitrogen-containing compounds, and esters , Inorganic acid esters, amides, glymes, ketones, sulfolanes such as sulfolane, oxazolidinones such as 3-methyl-2-oxazolidinone, mixed solvents of one or more kinds such as sultones Can.

  Specifically, as carbonates, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate and the like can be mentioned.

  Examples of ethers include trimethoxymethane, 1,2-dimethoxyethane, diethyl ether, 2-ethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran and the like.

  As oxolanes, 1,3-dioxolane, 4-methyl-1,3-dioxolane and the like can be mentioned.

  As nitrogen-containing compounds, acetonitrile, nitromethane, N-methyl-2-pyrrolidone and the like can be mentioned.

  Examples of esters include methyl formate, methyl acetate, ethyl acetate, butyl acetate, methyl propionate, ethyl propionate, phosphoric acid triester and the like.

  Examples of inorganic acid esters include sulfuric acid esters and nitric acid esters.

  Examples of the amides include dimethylformamide, dimethylacetamide and the like.

  Examples of glymes include diglyme, triglyme, tetraglyme and the like.

  Examples of ketones include acetone, diethyl ketone, methyl ethyl ketone, methyl isobutyl ketone and the like.

  Examples of sultones include 1,3-propane sultone, 4-butane sultone, naphtha sultone and the like.

As these non-aqueous electrolytes, in the case of a lithium ion secondary battery, non-aqueous electrolytes in which LiPF ₆ is dissolved in carbonates are preferable, and the electrolyte concentration varies depending on the electrode used and the electrolyte, but 0.5 to 3 mol / L is preferred.

  Hereinafter, the embodiment will be described in more detail by way of examples and comparative examples related to the embodiment of the present invention, but the embodiment is not limited thereto.

[Preparation of Binder Composition]
Example 1
In a temperature-controllable container with a stirrer,
100 parts by mass of water (hereinafter simply referred to as "part"),
Charge 0.2 parts of ammonium persulfate,
5 parts of 1,3-butylene glycol diacrylate as component (a),
(B) 3 parts of polyoxyethylene-1- (allyloxymethyl) alkylene sulfonic acid ester ammonium salt (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., trade name “Aqualon KH-10”) as a component (b)
5 parts of 2-hydroxyethyl methacrylate as component (c1),
81 parts of 2-ethylhexyl acrylate as component (c2),
5 parts of methyl methacrylate as component (c3),
5% of 0.8 parts of methacrylic acid as component (d) was added and polymerized at 80 ° C. for 6 hours. The polymerization conversion was 99%. The mixture was neutralized to pH 7 with a 10% aqueous potassium hydroxide solution to obtain a polymer emulsion having a solid content of 50% by mass. The solid content was measured in accordance with JIS K 6828-1: 2003.

Example 2
In a temperature-controllable container with a stirrer,
100 parts of water,
Charge 0.2 parts of ammonium persulfate,
6 parts of 1,6-hexanediol diacrylate as component (a) 80 parts of 2-ethylhexyl acrylate as component (c2),
The polymerization was carried out in the same manner as in Example 1 using the other components, polymerization conditions and procedures. The polymerization conversion was 99%. The mixture was neutralized to pH 7 with a 10% aqueous potassium hydroxide solution to obtain a polymer emulsion having a solid content of 50% by mass.

Example 3
In a temperature-controllable container with a stirrer,
100 parts of water,
Charge 0.2 parts of ammonium persulfate,
3 parts of 1,6-hexanediol diacrylate as component (a) 83 parts of 2-ethylhexyl acrylate as component (c2),
The polymerization was carried out in the same manner as in Example 1 using the other components, polymerization conditions and procedures. The polymerization conversion was 99%. The mixture was neutralized to pH 7 with a 10% aqueous potassium hydroxide solution to obtain a polymer emulsion having a solid content of 50% by mass.

Example 4
In a temperature-controllable container with a stirrer,
100 parts of water,
Charge 0.2 parts of ammonium persulfate,
8 parts of tricyclodecanedimethanol diacrylate as component (a) 78 parts of 2-ethylhexyl acrylate as component (c2),
The polymerization was carried out in the same manner as in Example 1 using the other components, polymerization conditions and procedures. The polymerization conversion was 99%. The mixture was neutralized to pH 7 with a 10% aqueous potassium hydroxide solution to obtain a polymer emulsion having a solid content of 50% by mass.

Comparative Example 1
In a temperature-controllable container with a stirrer,
100 parts of water,
Charge 0.2 parts of ammonium persulfate,
Ethylene glycol dimethacrylate 2 parts instead of component (a) 84 parts of 2-ethylhexyl acrylate as component (c2),
The polymerization was carried out in the same manner as in Example 1 using the other components, polymerization conditions and procedures. The polymerization conversion was 99%. The mixture was neutralized to pH 7 with a 10% aqueous potassium hydroxide solution to obtain a polymer emulsion having a solid content of 50% by mass.

  The ethylene glycol dimethacrylate used in Comparative Example 1 is not a compound corresponding to the component (a) of the present invention, but in Table 1 below, for the purpose of comparison, the composition comparison, calculation, etc. went. The comparative example 1 corresponds to the example 1 of the above-mentioned patent document 5 (however, the electrolytic solution is different).

Comparative Example 2
In a temperature-controllable container with a stirrer,
100 parts of water,
Charge 0.2 parts of ammonium persulfate,
7 parts of triethylene glycol diacrylate instead of the component (a) 79 parts of 2-ethylhexyl acrylate as the component (c2),
The polymerization was carried out in the same manner as in Example 1 using the other components, polymerization conditions and procedures. The polymerization conversion was 99%. The mixture was neutralized to pH 7 with a 10% aqueous potassium hydroxide solution to obtain a polymer emulsion having a solid content of 50% by mass.

  The triethylene glycol diacrylate used in Comparative Example 2 is not a compound corresponding to the component (a) of the present invention, but in the following table, for comparison, the composition comparison, calculation, etc. went.

[Evaluation of binder resin]
[Insoluble fraction and swelling ratio to diethyl carbonate]
The polymer emulsions obtained in Examples 1 to 4 and Comparative Examples 1 and 2 are dried in an environment at room temperature (about 25 ° C.), and then dried in a thermostat at 105 ° C. for 1 hour, to a thickness of 0. A resin film of 4 to 4 mm was produced. The produced film was cut, and the mass W ₀ of the cut film piece was measured. At this time, the initial weight W ₀ of the film piece was in the range of 0.09 to 0.12 g. Next, this film piece was immersed in diethyl carbonate having a purity of 99% or more (hereinafter sometimes abbreviated as “DEC”) at 60 ° C. for 1 hour. Thereafter, the film pieces were taken out of the DEC by filtering with a 200 mesh wire mesh, and the mass W ₁ of the film pieces immediately after taking out was measured. Thereafter, the film pieces were dried at room temperature (about 25 ° C.) for one week, and then dried in a thermostat at 105 ° C. for one hour, and the mass W _{2 of the} film pieces was measured. From the measured W ₀ , W ₁ and W ₂ , the insoluble fraction and the swelling ratio with respect to DEC were respectively calculated by the following formulas described above.
Insoluble fraction (%) = W ₂ / W ₀ × 100
Swelling capacity _{(%) = W 1 / W} 2 × 100

[Dynamic viscoelasticity measurement (crosslink density)]
The polymer emulsions obtained in Examples 1 to 4 and Comparative Examples 1 and 2 are dried in an environment at room temperature (about 25 ° C.), and then dried in a thermostat at 105 ° C. for 1 hour, to a thickness of 0. A resin film of 4 to 4 mm was produced. The produced film was cut to obtain a film piece for dynamic viscoelasticity measurement. The measurement was carried out with a dynamic viscoelasticity measuring device with this film piece.

The measurement of dynamic viscoelasticity measured the temperature dependence of dynamic shear storage elastic modulus in temperature change of 100 degreeC-100 degreeC (however, Examples 2-5 in 150 degreeC-50 degreeC). The film piece was set in a jig heated to 50 ° C., and measurement was performed. The temperature change at the time of measurement is 50 ° C at the time of setting, then the temperature is raised to 100 ° C (but 150 ° C in Examples 2-5), and then the dynamic shear storage elastic modulus is measured at -100 ° C (However, in Examples 2-5, the temperature was lowered to -50 ° C). At the time of temperature rising from the time of film setting to 100 ° C. (but 150 ° C. in Examples 2-5), a force of 0.5 N was applied to the film piece. When measuring the dynamic shear storage modulus from 100 ° C. to -100 ° C. (but for Examples 2-5 at 150 ° C. to -50 ° C.), a force of 1 N was applied to the piece of film. Moreover, the frequency at the time of measurement was fixed at 1 Hz, and distortion was measured at an initial 0.5% to a final 5 × 10 ⁻³ %.

  The dynamic shear storage modulus G ′ at a temperature of 100 ° C., which is a rubbery region, was read from the obtained temperature dependency measurement result of the dynamic shear storage modulus at a frequency of 1 Hz. The crosslink density was calculated from this G 'and the measurement temperature according to the above-mentioned equation.

[Glass transition temperature (Tg)]
The glass transition temperature (Tg) was measured by the method shown below.
The polymer emulsions obtained in Examples 1 to 4 and Comparative Examples 1 to 2 were respectively poured into molds and dried at 23 ° C. for 5 days to produce films of 0.3 to 0.5 mm in thickness. The produced film was used as a sample, and in accordance with JIS K 7121: 1987, DSC (Seiko Electronic Industry EXSTAR 6000 DSC-6200) was measured. The intersection of the tangent of the baseline in the obtained DSC curve and the tangent of the steeply falling position of the endothermic region due to the glass transition was read as Tg.

[Preparation of positive electrode material slurry]
The polymer emulsions obtained in Examples 1 to 4 and Comparative Examples 1 to 2 were mixed with 5 parts by solid content, 2 parts of carboxymethylcellulose, 84 parts of LiFePO ₄ , 7 parts of acetylene black and 2 parts of fibrous carbon, respectively. Thus, a positive electrode material slurry having a solid content of 42% was prepared.

[Evaluation of positive electrode material slurry]
[Slurry storage stability]
The prepared positive electrode material slurry was sealed and allowed to stand, and after one week, the slurry properties were confirmed. Occurrence of gelation or coarse particles, or occurrence of extreme viscosity change is not acceptable, no occurrence of coarse particles, no occurrence of coarse particles, low viscosity change, good viscosity change, but no occurrence of coarse particles Visual evaluation was performed with the items as "OK".

[Smoothness of Coating]
The prepared positive electrode material slurry was applied to a 200 μm-thick positive electrode current collector (aluminum foil). At that time, visual evaluation was performed with coarse particles with streaks on the coated surface as "not good", those without streaks as "good" and those with slight traces as "good". The

[Production of positive electrode]
Next, the prepared positive electrode material slurry is applied on one side of a 20 μm-thick positive electrode current collector (aluminum foil) so that the applied amount after drying is 140 g / m ^2, and this is dried to form a positive electrode. The agent layer was formed. The resultant was pressed with a roll press so that the thickness of the positive electrode mixture layer was 64 μm, and cut into a circle having a diameter of 14 mm to prepare a mixture electrode plate. In order to completely remove the residual solvent and non-volatiles, vacuum drying was performed at 120 ° C. for 14 hours to obtain a positive electrode. About the produced positive electrode, the adhesiveness (binding property) of the positive mix layer was evaluated by the following method.

[Evaluation of positive electrode]
[Peel test]
Using the produced positive electrode, a rectangle having a length of 200 cm and a width of 15 mm was cut out as a test piece in the coating direction. An adhesive tape (3M 895T) was attached to the front surface of the test piece on the positive electrode mixture layer side. The positive electrode current collector foil end was fixed, and the stress was measured when the tape end at one end of the test piece was pulled upward at a tensile speed of 200 mm / min. It was determined that the larger the stress, the larger the binding strength of the positive electrode mixture layer to the positive electrode current collector. Unit N / m.

[Preparation of lithium ion battery]
A lithium ion battery was manufactured using the above-prepared positive electrode and further using a disk-shaped lithium metal with a diameter of 15 mm as the negative electrode. The positive electrode and the negative electrode were inserted into a coin cell, and a mixed solution of LiPF ₆ as an electrolyte and ethylene carbonate / diethylene carbonate / dimethylene carbonate = 1/1/1/1 (volume ratio) was injected as an electrolyte into the coin cell. The coin cell was crimped and sealed to produce a coin-type half cell lithium ion battery.

[Evaluation of lithium ion battery]
The prepared lithium ion battery was subjected to constant current and constant voltage charging at 4.0C and 0.2ltA (188mA) at 25 ° C., and then discharged to 2.0V with a constant current of 0.2ltA.

[Evaluation of discharge rate characteristics (capacity maintenance rate)]
Next, the discharge current was changed to 0.2 ltA and 1 ltA, and the discharge capacity for each discharge current was measured. Recovery charge in each measurement was constant current constant voltage charging at 4.0 V (1 ltA cut). Then, the high-rate discharge capacity retention rate during 1 ltA discharge relative to 0.2 ltA discharge was calculated.

[Evaluation of cycle characteristics (capacity maintenance rate)]
At an environmental temperature of 25 ° C., constant current constant voltage charging at a charge voltage of 4.0 V and 1 ltA and constant current discharge at a final discharge voltage of 2.0 V at 1 ltA were performed. The cycle of charge and discharge was repeated, and the ratio of the discharge capacity at the 500th cycle to the discharge capacity at the first cycle was determined as the cycle capacity retention ratio.

  Each evaluation result is put together in following Table 1, and is shown.

[result]
As shown in Table 1, the binder compositions of Examples 1-4 use the diacrylate monomer represented by Formula I. Therefore, in the binder compositions of Examples 1 to 4, the insoluble matter ratio to DEC of the binder resin is 80% or more (more specifically, in the range of 80 to 99%), and the swelling of the binder resin to DEC is The magnification was 2000% or less (more specifically, in the range of 350 to 460%).

  Therefore, it is suggested that the binder compositions of Examples 1 to 4 can form a binder resin having good resistance to the electrolytic solution, and a positive electrode material slurry having excellent storage stability and smoothness of the coating film. I was able to get it. As a result, the lithium ion batteries of Examples 1 to 4 were both excellent in cycle characteristics and discharge rate characteristics. From these results, it was suggested that the binder composition according to the present technology can be suitably used as an electrode in a secondary battery or a capacitor, in particular, as a binder material for a lithium ion secondary battery.

  On the other hand, the binder composition of Comparative Example 1 uses ethylene glycol dimethacrylate monomer. Therefore, neither the insoluble matter ratio to DEC of the binder resin nor the swelling ratio gave a favorable result. As a result, the lithium ion battery of Comparative Example 1 was inferior in cycle characteristics and discharge rate characteristics to those of Examples.

  Furthermore, the binder composition of Comparative Example 2 is an ethylenic unsaturated carboxylic acid compound having a plurality of acrylic groups, and a triethylene glycol diacrylate monomer containing an ethylene glycol chain in a repeating structure is added. The viscosity increased when the slurry was blended, and neither the slurry storage stability nor the electrode plate coatability resulted in good results. In Comparative Example 2, the item “impossible” is an item that can not be measured because a dried product is brittle and uneven and a uniform film suitable for measurement can not be obtained.

  In the binder composition of Example 1, the insoluble matter ratio to DEC of the binder resin was 95% and the swelling ratio was 460%, and the discharge rate characteristics were good.

  In the binder compositions of Examples 2 and 3, the insoluble fraction of DEC to the binder resin is 95% or more, the swelling ratio is less than 400%, the discharge rate characteristics and the cycle characteristics are good, and particularly Example 3 The adhesion (binding) between the current collector and the active material was good.

  In the binder composition of Example 4, the insoluble matter ratio to DEC of the binder resin was 80% or more (more specifically, 80 to 99%), and the discharge rate characteristics were good. As a result, in Examples 1 to 4, it was confirmed that lithium ion batteries having good capacity retention rates such as cycle characteristics and discharge rate characteristics could be obtained.

  The binder resin for an electrode of the present invention makes the storage stability of the electrode material slurry and the smoothness of the coating film very good, and is particularly suitable for use as an aqueous binder. In addition, lithium ion secondary batteries, nickel-hydrogen secondary batteries, and electric batteries having excellent cycle characteristics and discharge rate characteristics have good resistance to the electrolyte and can suppress elution and swelling in the electrolyte. It is possible to obtain a multilayer capacitor or the like. The present invention is an industrially useful invention.

Claims (13)

(A) Ethylenically unsaturated carboxylic acid ester compound having a structure of the following formula I

(Wherein, -X- is a linear or branched alkylene group having 3 to 12 carbon atoms or a cycloalkylene group having 4 to 12 carbon atoms, and R ¹ and R ² are each independently a hydrogen atom or a methyl group Is)
Monomer units derived from
(B) a monomer unit derived from an ethylenically unsaturated sulfonic acid compound,
Containing polymers,
A binder resin composition for an electrode, wherein a crosslinking density of the polymer is 1 × 10 ⁻⁴ mol / cc or more and 1 × 10 ⁻³ mol / cc or less. The above-mentioned polymer is further contained as component (c),
(C1) a monomer unit derived from an ethylenically unsaturated carboxylic acid ester compound having a hydroxyl group at an alcohol-derived site in an ester structure,
The composition according to claim 1, which contains any one or more of monomer units derived from an ethylenically unsaturated carboxylic acid ester compound having an alkyl group having 8 or more carbon atoms in an alcohol-derived site in the ester structure (c2). Binder resin composition for electrodes.   The binder resin composition for electrodes of Claim 2 whose content of the monomer unit of (c1) component is 1-10 mass% in the said polymer.   The electrode according to claim 2 or 3, wherein in the polymer, the proportion of monomer units of component (c2) to the total of components (a) and (c) is 10 to 98.9 mass%. Binder resin composition.   The binder resin for electrodes as described in any one of Claims 1-4 whose content of the monomer unit of (a) component is 0.1-10 mass% with respect to the gross mass of the said polymer. Composition. In the above polymer, the mass ratio of the content of the monomer unit of the component (a) and the component (c) when present to the content of the monomer unit of the component (b) {(a) + (c)}: (B) is in the range of 98-91: 2-9,
In the above polymer, the ratio of the total amount of the monomer units of the component (a) and the monomer units of the component (b) and the monomer units of the component (c) is 70% by mass or more. The binder resin composition for electrodes as described in any one of Claims 1-5. Further, the above-mentioned polymer is used as the component (c)
The monomer unit derived from an ethylenically unsaturated carboxylic acid ester compound having an alkyl group having 1 to 7 carbon atoms at an alcohol-derived site in the ester structure (c3) is contained in an amount of 1 to 30% by mass. The binder resin composition for electrodes as described in any one of these. Further, the above-mentioned polymer is
The binder resin composition for electrodes as described in any one of Claims 1-7 which contains 0.1-10 mass% of monomer units originating in (d) an ethylenically unsaturated carboxylic acid compound.   The binder resin composition for electrodes according to any one of claims 1 to 8, wherein the binder resin for electrodes is in the form of a polymer emulsion in which particles of a polymer are dispersed in an aqueous solvent.   The electrode material slurry containing the binder resin composition for electrodes as described in any one of Claims 1-9, and an active material.   An electrode comprising the coated and dried layer of the electrode material slurry according to claim 10.   A secondary battery comprising the electrode according to claim 11.   An electric double layer capacitor comprising the electrode according to claim 11.