Negative electrode comprising vapor grown carbon fiber and polymer materials and nonaqueous electrolyte secondary battery

1. A negative electrode comprising:

a negative electrode mixture layer including:

a negative electrode active material;

a binder comprising a polymer containing vinylidene fluoride as a repeating unit and a polymer containing acrylonitrile as a repeating unit; and

a vapor-grown carbon fiber, wherein:

a content of the polymer containing acrylonitrile as a repeating unit is from 1 to 20% by mass relative to a total content of the polymer containing vinylidene fluoride as a repeating unit and the polymer containing acrylonitrile as a repeating unit, and

the polymer containing acrylonitrile as a repeating unit is selected from the group consisting of polyacrylonitrile, a copolymer having an acrylate group and a copolymer having an acrylamide group.

2. The negative electrode according to claim 1 , wherein

a total content of the polymer containing vinylidene fluoride as a repeating unit and the polymer containing acrylonitrile as a repeating unit is from 2.5 to 8% by mass relative to the total content of the negative electrode mixture layer.

3. The negative electrode according to claim 1 , wherein

a content of the vapor-grown carbon fiber in the negative electrode mixture layer is from 1 to 5% by mass relative to the total content of the negative electrode mixture layer.

4. The nonaqueous electrolyte secondary battery according to claim 1 , wherein the vapor-grown carbon fiber has an average fiber diameter of 150 nm and an average fiber length of 10-20 μm.

5. The negative electrode according to claim 1 , wherein a content of the vapor-grown carbon fiber in the negative electrode mixture layer is from 2 to 3.5% by mass relative to the total content of the negative electrode mixture layer.

6. The negative electrode according to claim 1 , wherein the polymer containing acrylonitrile as a repeating unit is polyacrylonitrile.

7. A nonaqueous electrolyte secondary battery comprising:

a positive electrode;

a negative electrode; and

a nonaqueous electrolyte, wherein

the negative electrode has a negative electrode mixture layer including a negative electrode active material; a binder comprising a polymer containing vinylidene fluoride as a repeating unit and a polymer containing acrylonitrile as a repeating unit; and a vapor-grown carbon fiber, wherein:

a content of the polymer containing acrylonitrile as a repeating unit is from 1 to 20% by mass relative to a total content of the polymer containing vinylidene fluoride as a repeating unit and the polymer containing acrylonitrile as a repeating unit

the nonaqueous electrolyte contains a fluorocarbon based polymer compound, and

the polymer containing acrylonitrile as a repeating unit is selected from the group consisting of polyacrylonitrile, a copolymer having an acrylate group and a copolymer having an acrylamide group.

8. The nonaqueous secondary electrolyte secondary battery according to claim 7 , wherein a total content of the polymer containing vinylidene fluoride as a repeating unit and the polymer containing acrylonitrile as a repeating units from 2.5 to 8% by mass relative to the total content of the negative electrode mixture layer.

9. The nonaqueous electrolyte secondary battery according to claim 7 , wherein a content of the vapor-grown carbon fiber in the negative electrode mixture layer is from 1 to 5% by mass relative to the total content of the negative electrode mixture layer.

10. The nonaqueous electrolyte secondary battery according to claim 7 , wherein the fluorocarbon based polymer compound is a copolymer of vinylidene fluoride and hexafluoropropylene containing from 3 to 7.5% by mass of hexafluoropropylene.

11. The nonaqueous electrolyte secondary battery according to claim 7 , wherein the vapor-grown carbon fiber has an average fiber diameter of 150 nm and an average fiber length of 10-20 μm.

12. The nonaqueous electrolyte secondary battery according to claim 7 , wherein a content of the vapor-grown carbon fiber in the negative electrode mixture layer is from 2 to 3.5% by mass relative to the total content of the negative electrode mixture layer.

13. The nonaqueous electrolyte secondary battery according to claim 7 , wherein the polymer containing acrylonitrile as a repeating unit is polyacrylonitrile.