Binder for electrode of lithium secondary cell

Patent metadata

Field	Value
Publication number	US-10026963-B2
Application number	US-201414903614-A
Country	US
Kind code	B2
Filing date	Jul 1, 2014
Priority date	Jul 18, 2013
Publication date	Jul 17, 2018
Grant date	Jul 17, 2018

Abstract

A binder for an electrode of a lithium secondary battery contains a polyurethane aqueous dispersion. The polyurethane aqueous dispersion contains a hydrophilic group-containing polyurethane obtained by using at least (A) an organic polyisocyanate and (B) a compound having one or more active hydrogen groups. (A) the organic polyisocyanate has a content of 50 mass % or more and 80 mass % or less based on the hydrophilic group-containing polyurethane. (B) the compound having one or more active hydrogen groups contains (B1) a compound having one or more active hydrogen groups and (B2) a compound having one or more active hydrogen groups and one or more ionic hydrophilic groups.

First claim

The invention claimed is:

1. A binder for an electrode of a lithium secondary battery, comprising a polyurethane aqueous dispersion, wherein
the polyurethane aqueous dispersion comprises a hydrophilic group-containing polyurethane obtained by using at least (A) an organic polyisocyanate and (B) a compound having one or more active hydrogen groups,
(A) the organic polyisocyanate has a content of 54.2 mass % or more and 80 mass % or less based on the hydrophilic group-containing polyurethane, and
(B) the compound having one or more active hydrogen groups comprises (B1) a compound having two or more active hydrogen groups and (B2) a compound having one or more active hydrogen groups and one or more ionic hydrophilic groups,
wherein the hydrophilic group-containing polyurethane has a crosslinking density of 0.3 or more and 1.0 or less per 1,000 molecular weights of the polyurethane, and
wherein the hydrophilic group-containing polyurethane comprises an aromatic ring structure or an alicyclic structure, and a total content ratio of the aromatic ring structure and the alicyclic structure is 40 mass % or more.

2. The binder for an electrode of a lithium secondary battery according to claim 1 , wherein (B) the compound having one or more active hydrogen groups has an average hydroxyl value of 300 mgKOH/g or more.

3. The binder for an electrode of a lithium secondary battery according to claim 1 , wherein when a coating film is formed from the hydrophilic group-containing polyurethane and dipped in an electrolytic solution under a condition of 60° C. for 3 days, a weight increase rate of the coating film is 50% or less.

4. The binder for an electrode of a lithium secondary battery according to claim 1 , wherein when a coating film is formed from the hydrophilic group-containing polyurethane and dipped in an electrolytic solution under a condition of 60° C. for 3 days, a modulus of elasticity at 60° C. of a swollen coating film is 10 MPa or more.

5. The binder for an electrode of a lithium secondary battery according to claim 1 , wherein when a coating film is formed from the hydrophilic group-containing polyurethane, dipped in an electrolytic solution under a condition of 60° C. for 3 days and then vacuum-dried at 80° C. for 24 hours, a weight loss rate of the coating film is 10% or less.

6. The binder for an electrode of a lithium secondary battery according to claim 1 , wherein the hydrophilic group-containing polyurethane has a crosslinking density of 0.41 or more and 1.0 or less per 1,000 molecular weights of the polyurethane.

Assignees

• Dai Ichi Kogyo Seiyaku Co Ltd

Inventors

• Takahashi Katsuo
• Miyamura Takeshi

Classifications

• C08G18/6659

  with compounds of group C08G18/34 · CPC title

• C08G18/755

  and at least one isocyanate or isothiocyanate group linked to a secondary carbon atom of the cycloaliphatic ring, e.g. isophorone diisocyanate · CPC title

• C09D175/04

  Polyurethanes · CPC title

• C08G18/758

  containing two or more cycloaliphatic rings · CPC title

• C08G18/6674

  with compounds of group C08G18/3203 · CPC title