Binder for battery electrodes, and electrode and battery using same
Provided is a binder for battery electrodes which includes a polymer including: structural units (1) derived from a (meth)acrylate monomer (A) having a hydroxyl group; structural units (2) derived from a polyfunctional (meth)acrylate monomer (B); and structural units (3) derived from a reactive surfactant (C). This binder is used to prepare electrodes, and produce batteries such as lithium ion secondary batteries. Provided are: an aqueous binder which has a low environmental impact, exhibits excellent binding properties, and, notably, does not cause oxidation degradation under an electrode environment; and an electrode and a battery which use said binder.
1. A battery electrode binder comprising a polymer comprising:
(I) structural units derived from a hydroxyl group-containing (meth)acrylate monomer (A) represented by the general formula,
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 1 to 30,
(II) structural units derived from a polyfunctional (meth) acrylate monomer (B), and
(III) structural units derived from a reactive surface active agent (C) which is at least one selected from a reactive anionic surface active agent, a reactive nonionic surface active agent, a reactive cationic surface active agent and a reactive amphoteric surface active agent,
wherein the reactive nonionic surface active agent is at least one selected from polyoxyalkylene alkenyl ether, polyoxyethylene alkyl propenylphenyl ether and α-hydro-ω-(1-alkoxymethyl-2-(2-propenyloxy)ethoxy)-poly(oxy-1,2-ethanediyl), and
the monomers used in the polymer do not have a carbon-carbon double bond including an aromatic carbon-carbon double bond and a carbon-carbon triple bond, other than ethylenically unsaturated double bonds contained in the (meth)acrylic group.
2. The battery electrode binder according to claim 1 , wherein the hydroxyl group-containing (meth)acrylate monomer (A) is an alkylene glycol mono(meth)acrylate having a molecular weight of 100 to 1,000.
3. The battery electrode binder according to claim 1 , wherein the polyfunctional (meth)acrylate monomer (B) is di-functional to penta-functional (meth)acrylates.
4. The battery electrode binder according to claim 1 , wherein the polyfunctional (meth)acrylate monomer (B) is a compound represented by the formula:
wherein, R 11 each is, the same or different, 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 of 5 or less.
5. The battery electrode binder according to claim 1 , wherein the reactive surface active agent (C) is a compound which has an ethylenically unsaturated double bond and a group exhibiting surface activity.
6. The battery electrode binder according to claim 1 , wherein the reactive surface active agent (C) is a reactive anionic surface active agent or a reactive nonionic surface active agent.
7. The battery electrode binder according to claim 1 , wherein the polymer further comprises one or both of:
(IV) structural units derived from a (meth)acrylate ester monomer (D), and
(V) structural units derived from a (meth)acrylic acid monomer (E).
8. The battery electrode binder according to claim 7 , wherein the (meth)acrylate ester monomer (D) is a compound represented by the formula:
wherein R 21 is hydrogen or a methyl group, and
R 22 is a hydrocarbon group having 1 to 50 carbon atoms,
and
the (meth)acrylic acid monomer (E) is a compound represented by the formula:
wherein R 31 is hydrogen or a methyl group.
9. The battery electrode binder according to claim 7 , wherein the amounts of the structural units derived from the monomers (A) to (E) are (A) 10 to 90 wt %, (B) 1 to 70 wt %, (C) 0.01 to 25 wt % and (D) 0 to 70 wt % and (E) 0 to 70 wt %, based on the polymer.
10. The battery electrode binder according to claim 1 , wherein a battery is a secondary battery.
11. A battery electrode comprising the binder according to claim 1 , and an active material.
12. A battery comprising the battery electrode according to claim 11 .
13. The battery electrode binder according to claim 6 , wherein the reactive anionic surface active agent is at least one selected from the group consisting of a sulfate ester-type, a sulfonic acid-type, a carboxylic acid-type, a phosphate ester-type alkali metal salt, alkaline earth metal salt, alkanolamine salt and ammonium salt.
14. The battery electrode binder according to claim 6 , wherein the reactive anionic surface active agent is a sulfate ester-type alkali metal salt, alkaline earth metal salt, alkanolamine salt or ammonium salt.
15. The battery electrode binder according to claim 7 , wherein the polymer consists of essentially of:
the structural units (I), (II) and (III), and optionally
at least one of the structural units (IV) and (V).