Graphene oxide, positive electrode for nonaqueous secondary battery using graphene oxide, method of manufacturing positive electrode for nonaqueous secondary battery, nonaqueous secondary battery, and electronic device

Patent metadata

Field	Value
Publication number	US-9293770-B2
Application number	US-201313826710-A
Country	US
Kind code	B2
Filing date	Mar 14, 2013
Priority date	Apr 10, 2012
Publication date	Mar 22, 2016
Grant date	Mar 22, 2016

Abstract

A graphene oxide used as a raw material of a conductive additive for forming an active material layer with high electron conductivity with a small amount of a conductive additive is provided. A positive electrode for a nonaqueous secondary battery using the graphene oxide as a conductive additive is provided. The graphene oxide is used as a raw material of a conductive additive in a positive electrode for a nonaqueous secondary battery and, in the graphene oxide, the atomic ratio of oxygen to carbon is greater than or equal to 0.405.

First claim

The invention claimed is:

1. A method of manufacturing a positive electrode for a nonaqueous secondary battery, comprising:
forming a paste including a dispersion medium, a plurality of active materials, a plurality of graphene oxides and a binding agent, wherein an atomic ratio of oxygen to carbon in the plurality of graphene oxides is 0.405 or more;
applying the paste on a current collector; and
reducing the plurality of graphene oxides after or at the same time when the dispersion medium included in the applied paste is volatilized, whereby an active material layer comprising a plurality of graphenes is formed over the current collector.

2. The method of manufacturing a positive electrode for a nonaqueous secondary battery according to claim 1 ,
wherein the paste is manufactured by the following steps:
dispersing the plurality of graphene oxides into the dispersion medium,
adding the plurality of active materials to the dispersion medium into which the plurality of graphene oxides are dispersed and performing mixing to form a mixture; and
adding the binding agent to the mixture and performing mixing.

3. The method of manufacturing a positive electrode for a nonaqueous secondary battery according to claim 1 ,
wherein the plurality of graphene oxides comprise one or more groups selected from an epoxy group, a carbonyl group, a carboxyl group, and a hydroxyl group.

4. The method of manufacturing a positive electrode for a nonaqueous secondary battery according to claim 1 ,
wherein the plurality of active materials are lithium iron phosphate.

5. The method of manufacturing a positive electrode for a nonaqueous secondary battery according to claim 1 ,
wherein a compounding ratio of A:B:C=X:Y:Z is satisfied in the paste, where A is the plurality of graphene oxides, B is the plurality of active materials, C is the binding agent, X is 2 to 10, Y is 85 to 93, and Z is 1 to 5.

6. The method of manufacturing a positive electrode for a nonaqueous secondary battery according to claim 1 ,
wherein a compounding ratio of A:B:C=P:Q:R is satisfied in the active material layer, where A is the plurality of graphenes, B is the plurality of active materials, C is the binding agent, P is 1 to 5, Q is 90 to 94, and R is 1 to 5.

7. The method of manufacturing a positive electrode for a nonaqueous secondary battery according to claim 1 ,
wherein, in the active material layer:
at least one of the plurality of graphenes is larger than an average particle diameter of the plurality of active materials,
the plurality of graphenes are dispersed in the active material layer such that at least one of the plurality of graphenes makes surface contact with one or more adjacent graphenes, and
at least one of the plurality of graphenes makes surface contact with at least one of the plurality of active materials in such a way as to wrap part of a surface thereof.

8. A method of manufacturing a positive electrode for a nonaqueous secondary battery, comprising:
forming a paste including a dispersion medium, a plurality of active materials, a plurality of graphene oxides and a binding agent, wherein an atomic ratio of oxygen to carbon in the plurality of graphene oxides is 0.405 or more;
applying the paste on a current collector; and
electrochemically reducing the plurality of graphene oxides after the dispersion medium included in the applied paste is volatilized, whereby an active material layer comprising a plurality of graphenes is formed over the current collector,
wherein, as bonding states of carbon included in the active material layer, a proportion of a C═C bond is 35% or more and a proportion of a C—O bond is 5% or more and 20% or less.

9. The method of manufacturing a positive electrode for a nonaqueous secondary battery according to claim 8 ,
wherein the paste is manufactured by the following steps:
dispersing the plurality of graphene oxides into the dispersion medium,
adding the plurality of active materials to the dispersion medium into which the plurality of graphene oxides are dispersed and performing mixing to form a mixture; and
adding the binding agent to the mixture and performing mixing.

10. The method of manufacturing a positive electrode for a nonaqueous secondary battery according to claim 8 ,
wherein, in the active material layer:
at least one of the plurality of graphenes is larger than an average particle diameter of the plurality of active materials,
the plurality of graphenes are dispersed in the active material layer such that at least one of the plurality of graphenes makes surface contact with one or more adjacent graphenes, and
at least one of the plurality of graphenes makes surface contact with at least one of the plurality of active materials in such a way as to wrap part of a surface thereof.

11. The method of manufacturing a positive electrode for a nonaqueous secondary battery according to claim 8 ,
wherein the plurality of graphene oxides comprise one or more groups selected from an epoxy group, a carbonyl group, a carboxyl group, and a hydroxyl group.

12. The method of manufacturing a positive electrode for a nonaqueous secondary battery according to claim 8 ,
wherein the plurality of active materials are lithium iron phosphate.

13. The method of manufacturing a positive electrode for a nonaqueous secondary battery according to claim 8 ,
wherein a compounding ratio of A:B:C=X:Y:Z is satisfied in the paste, where A is the plurality of graphene oxides, B is the plurality of active materials, C is the binding agent, X is 2 to 10, Y is 85 to 93, and Z is 1 to 5.

14. The method of manufacturing a positive electrode for a nonaqueous secondary battery according to claim 8 ,
wherein a compounding ratio of A:B:C=P:Q:R is satisfied in the active material layer, where A is the plurality of graphenes, B is the plurality of active materials, C is the binding agent, P is 1 to 5, Q is 90 to 94, and R is 1 to 5.

Assignees

• Semiconductor Energy Lab

Inventors

• Todoriki Hiroatsu
• Yukawa Mikio
• Saito Yumiko
• Yamakaji Masaki
• Yatabe Rika
• Ikenuma Tatsuya

Classifications

• H01M10/052

  Li-accumulators · CPC title

• H01M4/625 Primary

  Carbon or graphite · CPC title

• H01M4/136

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

• H01M4/624

  Electric conductive fillers · CPC title

• H01M4/364

  as mixtures · CPC title