Binder for battery electrode, and electrode and battery using same
This binder for battery electrodes is characterized by containing a polymer including: (A) a structural unit represented by general formula (1) and derived from a monomer having a hydroxyl group (in the formula, R1 is a hydrogen or a C1-C4 straight-chain or branched alkyl group, R2 and R3 are each a hydrogen or a C1-C4 straight-chained or branched alkyl group, and n is an integer of 2-30); (B) a structural unit derived from an ethylenically unsaturated monomer having at least one functional group selected from the group consisting of a difunctional carboxylic acid group, a nitrile group and a ketone group; and (C) a structural unit derived from a polyfunctional (meth)acrylate monomer having at most five functional groups.
1. A binder for battery electrode, comprising a polymer comprising:
1 to 89.9% by weight of (A) constitutional units derived from a monomer having a hydroxyl group, of the formula (1):
wherein R 1 is hydrogen, or a linear or branched alkyl group having 1 to 4 carbon atoms,
R 2 and R 3 each is hydrogen, or a linear or branched alkyl group having 1 to 4 carbon atoms, and
n is an integer of 2 to 30,
40 to 10% by weight of (B) constitutional units derived from an ethylenically unsaturated monomer having at least one functional group selected from the group consisting of a difunctional carboxylic acid group, a nitrile group and a ketone group, and
20 to 0.1% by weight of (C) constitutional units derived from a polyfunctional (meth)acrylate monomer having penta- or less functionality.
2. The binder for battery electrode according to claim 1 , wherein n is an integer of 4 to 20, in the formula (1).
3. The binder for battery electrode according to claim 1 , wherein the functional group-containing ethylenically unsaturated monomer (B) is a compound of the formula (2):
(A 1 -)(A 2 -)C═C(-A 3 )(-A 4 ) (2)
wherein A 1 is a group having a nitrile group (—CN group), a carboxylic acid group (—COOH group) or a ketone group (>C═O group),
A 2 and A 3 are each independently a hydrogen atom, a halogen atom, an alkyl group having 1-6 carbon atoms, or a group having a nitrile group (—CN group) or a carboxylic acid group (—COOH group),
A 4 is a hydrogen atom, a halogen atom, or an alkyl group having 1-6 carbon atoms, and
A 1 and A 2 , or A 1 and A 3 may be joined together to form a cyclic hydrocarbon group having two carboxylic acid groups.
4. The binder for battery electrode according to claim 1 , wherein the group having a nitrile group (—CN group) is a —B—CN group wherein B 2 is a direct bond or an alkylene group having 1-6 carbon atoms,
the group having a difunctional carboxylic acid group (—COOH group) (dicarboxylic acid group) is a —B 1 —COOH group wherein B 1 is a direct bond or an alkylene group having 1-6 carbon atoms, and
the group having a ketone group (>C═O group) is a —B 3 —CO—B 4 group wherein B 3 is a direct bond or an alkylene group having 1-6 carbon atoms, and B 4 is an alkyl group having 1-6 carbon atoms.
5. The binder for battery electrode according to claim 1 , wherein the ethylenically unsaturated monomer having a nitrile group (—CN group) is a compound of the formula:
(CN—)(X 11 —)C═C(—X 12 )(—X 13 )
wherein X 11 is a hydrogen atom, an alkyl group having 1-6 carbon atoms, a halogen atom or a cyano group,
X 12 is a hydrogen atom, an alkyl group having 1-6 carbon atoms or a cyano group, and
X 13 is a hydrogen atom, an alkyl group having 1-6 carbon atoms or a halogen atom.
6. The binder for battery electrode according to claim 1 , wherein the ethylenically unsaturated monomer having a difunctional carboxylic acid group is a compound of the formula:
(HOOC—X 21 —)(HOOC—X 22 —) m (—X 23 ) 1-m C═C(—X 22 —COOH) 1-m (—X 23 ) m (—X 24 )
wherein X 21 and X 22 are each independently a direct bond or an alkylene group having 1-6 carbon atoms,
X 23 and X 24 are each independently a hydrogen atom, an alkyl group having 1-6 carbon atoms or a halogen atom, and
m is 0 or 1.
7. The binder for battery electrode according to claim 1 , wherein the ethylenically unsaturated monomer having a ketone group is a compound of the formula:
(X 31 —CO—X 32 —)(X 33 —)C═C(—X 34 )(—X 35 )
wherein X 31 , X 33 , X 34 and X 35 are each independently a hydrogen atom, an alkyl group having 1-6 carbon atoms or a halogen atom, and
X 32 is a direct bond or an alkylene group having 1-6 carbon atoms.
8. The binder for battery electrode according to claim 1 , wherein the polyfunctional (meth)acrylate monomer (C) is a compound of the formula (3):
wherein R 11 is independently hydrogen or a methyl group,
R 12 is a penta- or less valent organic group having 2 to 100 carbon atoms, and
m is an integer less than or equal to 5.
9. The binder for battery electrode according to claim 1 , wherein the polyfunctional (meth)acrylate (C) is a (meth)acrylate having tri-functionality to penta-functionality.
10. The binder for battery electrodes according to claim 1 , wherein the polymer further comprises one or both of constitutional units (D) derived from a (meth)acrylate ester monomer and constitutional units (E) derived from a (meth)acrylic acid monomer.
11. The binder for battery electrode according to claim 10 , wherein the (meth)acrylate ester monomer (D) is a compound of the formula (4):
wherein R 21 is hydrogen or a methyl group, and
R 22 is a hydrocarbon group having 1 to 50 carbon atoms.
12. The binder for battery electrode according to claim 10 , wherein the (meth)acrylic acid monomer (E) is a compound of the formula (5):
wherein R 31 is hydrogen or a methyl group.
13. The binder for battery electrode according to claim 1 , wherein the battery is a secondary battery.
14. A battery electrode comprising the binder according to claim 1 , and an active material.
15. A battery comprising the electrode according to claim 14 .