POROUS FILM FOR SEPARATOR, BATTERY SEPARATOR, BATTERY ELECTRODE, AND MANUFACTURING METHODS THEREFOR, AND LITHIUM SECONDARY BATTERY

• US 20110039145A1
• Filed: 06/09/2009
• Published: 02/17/2011
• Est. Priority Date: 07/04/2007
• Status: Active Grant

• Current Assignee: Maxell, Ltd.
• Original Assignee: Hitachi Maxell Limited (Maxell, Ltd.)
• Inventors: Abe, Toshihiro, Abe, Hiroshi, Matsumoto, Nobuaki, Katayama, Hideaki
• Granted Patent: US 8,920,960 B2
• Time in Patent Office: Days
• US Class Current: 429/144
• CPC Class Codes: H01M 10/052 Li-accumulators
• CPC Class Codes: H01M 50/403 Manufacturing processes of separators, membranes or diaphragms
• CPC Class Codes: H01M 50/417 Polyolefins
• CPC Class Codes: H01M 50/44 Fibrous material
• CPC Class Codes: H01M 50/446 Composite material consisting of a mixture of organic and inorganic materials
• CPC Class Codes: H01M 50/449 having a layered structure
• CPC Class Codes: H01M 50/491 Porosity
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product

Abstract

The present invention provides a lithium secondary battery using a separator including a porous film formed by binding inorganic oxide particles together with a binder. The inorganic oxide particles are treated so that an amount of alkali metal elements eluted therefrom when they are immersed in ion exchange water is reduced to 1000 ppm or less. As a result, it is possible to provide a lithium secondary battery with a high degree of reliability, whose characteristics deteriorate less when it is used or stored for an extended period.

Claims

1. A porous film for a separator comprising inorganic oxide particles and a binder for binding the inorganic oxide particles together,

wherein the inorganic oxide particles include boehmite, and

an amount of Na contained in the porous film is 1000 ppm or less.

2. The porous film for a separator according to claim 1, wherein a total amount of alkali metal elements contained in the porous film is 1000 ppm or less.

3. The porous film for a separator according to claim 1, wherein an amount of Na included in the inorganic oxide particles is 600 ppm or less.

4. The porous film for a separator according to claim 1, wherein the inorganic oxide particles include plate-like particles.

5. The porous film for a separator according to claim 1, wherein a proportion of the inorganic oxide particles is 50% by volume or more.

6. The porous film for a separator according to claim 1, wherein a proportion of the inorganic oxide particles is 99.5% by volume or less.

7. The porous film for a separator according to claim 1, wherein an average particle size of the inorganic oxide particles is in a range of 0.01 μ

m to 10 μ

m.

8. The porous film for a separator according to claim 1, wherein the porous film for a separator has a thickness of 1 μ

m or more.

9. The porous film for a separator according to claim 8, wherein the porous film for a separator has a thickness of 3 μ

m or more.

10. The porous film for a separator according to claim 1, wherein the porous film for a separator has a thickness of 10 μ

m or less.

11. A battery separator comprising the porous film for a separator according to claim 1 and a microporous film including a heat-melting resin layer having a melting point of 80 to 140°

C.

12. The battery separator according to claim 11, wherein the porous film for a separator is formed on the microporous film.

13. The battery separator according to claim 11, wherein a thickness of the porous film for a separator is 10% or more of a thickness of the microporous film.

14. The battery separator according to claim 11, wherein a thickness of the porous film for a separator is 50% or less of a thickness of the microporous film.

15. The battery separator according to claim 11, wherein the microporous film has a thickness of 30 μ

m or less.

16. The battery separator according to claim 11, wherein the melting point of the heat-melting resin is 130°

C. or less.

17. The battery separator according to claim 11, wherein a proportion of the inorganic oxide particles is 10% by volume or more.

18. The battery separator according to claim 17, wherein the proportion of the inorganic oxide particles is 30% by volume or more.

19. The battery separator according to claim 11, wherein a proportion of the inorganic oxide particles is 80% by volume or less.

20. The battery separator according to claim 11, wherein the battery separator has a thickness of 50 μ

m or less.

21. A battery electrode comprising an active material containing layer and the porous film for a separator according to claim 1,

wherein the active material layer and the porous film for a separator are integrated with each other.

22. A lithium secondary battery comprising a positive electrode, a negative electrode, a separator and a nonaqueous electrolyte,

wherein the separator is the battery separator according to claim 11.

23. A lithium secondary battery comprising a positive electrode, a negative electrode, a separator and a nonaqueous electrolyte,

wherein at least one of the positive electrode and the negative electrode is the battery electrode according to claim 21.

24. A method for manufacturing a porous film for a separator, comprising steps of:

washing inorganic oxide particles with water to reduce an amount of alkali metal elements included in the inorganic oxide particles to 1000 ppm or less; and

binding the inorganic oxide particles together with a binder to form a porous film containing the inorganic oxide particles.

25. The method for manufacturing a porous film for a separator according to claim 24, wherein the inorganic oxide particles include boehmite.

26. A method for manufacturing a battery separator, comprising steps of:

washing inorganic oxide particles with water to reduce an amount of alkali metal elements included in the inorganic oxide particles to 1000 ppm or less; and

binding the inorganic oxide particles together with a binder to form a porous film containing the inorganic oxide particles on a microporous film including a heat-melting resin layer having a melting point of 80 to 140°

C.

27. A method for manufacturing a battery electrode, comprising steps of:

washing inorganic oxide particles with water to reduce an amount of alkali metal elements included in the inorganic oxide particles to 1000 ppm or less; and

binding the inorganic oxide particles together with a binder to form a porous film containing the inorganic oxide particles on an electrode including an active material containing layer.