Cathode binder composition, cathode slurry, cathode, and lithium ion secondary battery

Patent metadata

Field	Value
Publication number	US-9941518-B2
Application number	US-201415028115-A
Country	US
Kind code	B2
Filing date	Oct 6, 2014
Priority date	Oct 9, 2013
Publication date	Apr 10, 2018
Grant date	Apr 10, 2018

Abstract

Cathode binder composition having excellent binding properties and oxidation resistance. Also, cathode slurry, cathode, and lithium ion secondary battery produced using the cathode binder composition. The cathode binder composition contains a graft copolymer in which a monomer containing acrylonitrile as the main component is grafted onto polyvinyl alcohol having an average degree of polymerization of 300 to 3000 and a degree of saponification of 70 to 100% by mol. The cathode slurry contains the cathode binder composition, a cathode active material, and a conductive auxiliary. The cathode is produced using the cathode slurry. The lithium ion secondary battery contains a cathode prepared in this manner.

First claim

The invention claimed is:

1. A cathode binder composition, comprising: a graft copolymer in which a monomer containing acrylonitrile as a main component of 50% by mass or more and optionally one or more monomers selected from the group consisting of ethylenically unsaturated carboxylic acid esters, ethylenically unsaturated carboxylic acids, and styrene is grafted onto polyvinyl alcohol having an average degree of polymerization of 300 to 3000 and a degree of saponification of 70 to 100% by mol.

2. The cathode binder composition according to claim 1 , wherein a graft ratio of the graft copolymer is 20 to 150% and a weight average molecular weight of a homopolymer of polyacrylonitrile generated in the graft copolymerization is 30000 to 250000.

3. The cathode binder composition according to claim 2 , wherein an amount of the polyvinyl alcohol is 40 to 80% by mass and an amount of the polyacrylonitrile is 60 to 20% by mass in the graft copolymer.

4. A cathode slurry, comprising:
the binder composition according to claim 1 ;
a cathode active material; and
a conductive auxiliary.

5. The cathode slurry according to claim 4 , wherein the cathode active material contains at least one kind selected from the group consisting of LiCoO 2 , LiNiO 2 , Li(Co X Ni Y Mn Z )O 2 (wherein 0<X<1, 0<Y<1, 0<Z<1, and X+Y+Z=1), Li(Ni X Al Y Co Z )O 2 (wherein 0<X<1, 0<Y<1, 0<Z<1, and X+Y+Z=1), LiMn 2 O 4 , LiNi X Mn (2−X) O 4 (wherein 0<X<2), LiFePO 4 , LiMnPO 4 , LiFe X Mn (1−X) PO 4 (wherein 0<X<1), LiCoPO 4 , Li 3 V 2 (PO 4 ) 3 , and LiNiPO 4 .

6. The cathode slurry according to claim 4 , wherein the conductive auxiliary includes at least one or more kinds selected from the group consisting of
(i) fibrous carbon,
(ii) carbon black, and
(iii) a carbon composite in which the fibrous carbon and the carbon black are connected to each other.

7. A cathode, which is produced using the cathode slurry according to claim 4 .

8. A lithium ion secondary battery, comprising the cathode according to claim 7 .

Assignees

• Denka Company Ltd

Inventors

• Sakurai Yasuaki
• Yoshida Jun
• Watanabe Jun

Classifications

• H01M4/525

  of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy · CPC title

• H01M4/5825

  Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines · CPC title

• H01M4/136

  Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy · CPC title

• C08F261/04

  on to polymers of vinyl alcohol · CPC title

• H01M10/0525

  Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries · CPC title