LITHIUM SECONDARY BATTERY AND METHOD OF MANUFACTURING THE SAME

• US 20080124631A1
• Filed: 06/29/2007
• Published: 05/29/2008
• Est. Priority Date: 06/30/2006
• Status: Active Grant

• Current Assignee: Panasonic Energy (Shanghai) Co., Ltd. (Panasonic Holdings Corporation)
• Original Assignee: Sanyo Electric Company Limited (Panasonic Holdings Corporation)
• Inventors: Kusumoto, Yasuyuki, Torimae, Mariko, Minami, Hiroshi, Fukui, Atsushi
• Granted Patent: US 8,771,873 B2
• Time in Patent Office: Days
• US Class Current: 429/217
• CPC Class Codes: H01M 2004/027 Negative electrodes
• CPC Class Codes: H01M 4/0404 by coating on electrode collectors
• CPC Class Codes: H01M 4/134 Electrodes based on metals, Si or alloys
• CPC Class Codes: H01M 4/38 of elements or alloys
• CPC Class Codes: H01M 4/505 of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
• CPC Class Codes: H01M 4/525 of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
• CPC Class Codes: H01M 4/587 for inserting or intercalating light metals
• CPC Class Codes: H01M 4/622 being polymers
• CPC Class Codes: H01M 4/625 Carbon or graphite
• CPC Class Codes: H01M 4/64 Carriers or collectors
• CPC Class Codes: H01M 4/661 Metal or alloys, e.g. alloy coatings H01M4/669 take precedence
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A lithium secondary battery includes an electrode assembly having a positive electrode (1), a negative electrode (2) having a negative electrode current collector and a negative electrode active material layer formed on a surface of the negative electrode current collector and composed of a binder and negative electrode active material particles containing silicon and/or a silicon alloy, and a separator (3) interposed between the electrodes. The electrode assembly is impregnated with a non-aqueous electrolyte. The binder contains a polyimide resin represented by the following chemical formula (1):

where R contains at least a benzene ring, and n is within the range of from 10 to 100,000, and the negative electrode active material particles have an average particle size of 5 μm or greater.

Claims

1. A lithium secondary battery comprising:

a positive electrode;

a negative electrode comprising a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector, the negative electrode active material layer comprising a binder and negative electrode active material particles containing silicon particles and/or silicon alloy particles;

a separator interposed between the electrodes; and

an electrode assembly comprising the positive electrode, the negative electrode, and the separator; and

a non-aqueous electrolyte impregnated in the electrode assembly, wherein

the binder contains a polyimide resin represented by the following chemical formula (1);

2. The lithium secondary battery according to claim 1, wherein R in the chemical formula (1) is a functional group represented by the following chemical formula (2) or (3):

3. The lithium secondary battery according to claim 1, wherein the polyimide resin represented by the chemical formula (1) has a molecular weight of 100,000 or less.

4. The lithium secondary battery according to claim 1, wherein the negative electrode current collector has a surface roughness Ra of 0.2 μ

m or greater.

5. The lithium secondary battery according to claim 1, wherein the negative electrode current collector is selected from the group consisting of a copper foil, a copper alloy foil, a metal foil having a copper layer formed on its surface, and a metal foil having a copper alloy layer formed on its surface.

6. The lithium secondary battery according to claim 1, wherein the positive electrode contains a positive electrode active material comprising a lithium-transition metal composite oxide.

7. The lithium secondary battery according to claim 6, wherein the lithium-transition metal composite oxide is a lithium-transition metal composite oxide represented by the chemical formula Li_aNi_xMn_yCO_zO₂, wherein 0≦

a≦

1, x+y+z=1, 0≦

x≦

1, 0≦

y≦

1, and 0≦

z≦

1.

8. The lithium secondary battery according to claim 6, wherein the theoretical electrical capacity ratio of the positive electrode to the negative electrode is 1.2 or less.

9. The lithium secondary battery according to claim 1, wherein the silicon particles and the silicon alloy particles have an average particle size of 25 μ

m or less.

10. The lithium secondary battery according to claim 1, wherein the silicon particles and the silicon alloy particles have a crystallite size of 100 nm or less.

11. The lithium secondary battery according to claim 10, wherein the silicon particles and the silicon alloy particles are prepared by thermally decomposing or thermally reducing a material containing a silane compound.

12. The lithium secondary battery according to claim 11, wherein the silicon particles and/or the silicon alloy particles are prepared by pulverizing an ingot of silicon and/or an ingot of a silicon alloy that is/are prepared by thermally decomposing or thermally reducing a material containing a silane compound, and classifying the pulverized material.

13. The lithium secondary battery according to claim 11, wherein the silane compound is monosilane and/or trichlorosilane.

14. The lithium secondary battery according to claim 1, wherein the negative electrode active material layer contains 3 weight % to 20 weight %, based on the weight of the negative electrode active material, of graphite powder having an average particle size of from 3 μ

m to 15 μ

m.

15. The lithium secondary battery according to claim 1, wherein the negative electrode active material particles comprise silicon particles having a purity of 95 weight % or greater.

16. A method of manufacturing a lithium secondary battery, comprising:

dispersing negative electrode active material particles containing silicon particles and/or silicon alloy particles in a solution containing a binder precursor to prepare a negative electrode active material slurry;

applying the negative electrode active material slurry onto a surface of a negative electrode current collector;

heat-treating the negative electrode current collector on which the negative electrode active material slurry is applied under a non-oxidizing atmosphere to polymerize the binder precursor, so as to prepare a negative electrode containing as a binder a polyimide resin represented by the following chemical formula (1);

17. The method according to claim 16, wherein R in the chemical formula (1) is a functional group represented by the following chemical formula (2) or (3):

18. The method according to claim 16, wherein the binder precursor comprises a mixture of a diamine component and an esterified product of an acid anhydride component by an alcohol.

19. The method according to claim 18, wherein the heat-treating is conducted at a temperature higher than the glass transition temperature of the polyimide resin.

20. The method according to claim 19, wherein R in the chemical formula (1) of the polyimide resin is a functional group represented by the chemical formula (2), and the temperature of the heat-treating is within the range of from 300°

C. to 450°

C.

21. The method according to claim 19, wherein R in the chemical formula (1) of the polyimide resin is a functional group represented by the chemical formula (3), and the temperature of the heat-treating is within the range of from 275°

C. to 450°

C.

22. The method according to claim 16, wherein the silicon particles and the silicon alloy particles are prepared by thermally decomposing or thermally reducing a material containing a silane compound.

23. The method according to claim 22, wherein the silicon particles and/or the silicon alloy particles are prepared by pulverizing an ingot of silicon and/or an ingot of a silicon alloy that is/are prepared by thermally decomposing or thermally reducing a material containing a silane compound, and classifying the pulverized material.

24. The method according to claim 22, wherein the silane compound is monosilane and/or trichlorosilane.