Lithium secondary battery

• US 6,620,553 B2
• Filed: 07/10/2001
• Issued: 09/16/2003
• Est. Priority Date: 07/10/2000
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kasiha Toyota CHUO Kenkyusho, Kabushiki Kaisha Toyota Chuo Kenkyusho (Toyota Motor Corporation)
• Original Assignee: Kabushiki Kaisha Toyota Chuo Kenkyusho (Toyota Motor Corporation)
• Inventors: Shiga, Tohru, Koiwai, Akihiko, Kawauchi, Shigehiro
• Primary Examiner(s): Gulakowski, Randy
• Assistant Examiner(s): WILLS, MONIQUE M
• Application Number:
  US09/900,875
• Publication Number:
  US 20020018926A1
• Time in Patent Office: 798 Days
• Field of Search: 429/188, 429/303, 429/324, 429/327, 429/330, 429/331, 429/332, 429/333, 429/334, 429/335, 429/336, 429/337, 429/338, 429/347
• US Class Current: 429/303
• CPC Class Codes: H01M 10/0525 Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
• CPC Class Codes: H01M 10/0565 Polymeric materials, e.g. gel-type or solid-type
• CPC Class Codes: H01M 10/4235 Safety or regulating additives or arrangements in electrodes, separators or electrolyte H01M10/4242 takes precedence
• CPC Class Codes: H01M 10/446 Initial charging measures
• CPC Class Codes: H01M 2300/004 Three solvents
• CPC Class Codes: H01M 4/13 Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
• CPC Class Codes: H01M 4/485 of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy H01M4/505, H01M4/525 take precedence
• CPC Class Codes: H01M 4/587 for inserting or intercalating light metals
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries

Abstract

A lithium secondary battery exhibiting very high safety, which is ensured by restraining both the generation of flammable gas caused by the decomposition of an electrolyte, and the emission of oxygen from a positive active material even during overcharging. The lithium secondary battery includes a positive electrode of which an active material is a lithium transition metal composite oxide, a negative electrode of which an active material is a carbon material, and a nonaqueous electrolyte containing an organic solvent in which a lithium salt is dissolved. The nonaqueous electrolyte contains at least one kind of conductive polymer-forming monomers which have an alkyl group and is electrochemically polymerizable on the positive electrode within a battery operation voltage, and at least one kind of film-forming agents which electrochemically decompose within the battery operation voltage to form films on a surface of the negative electrode.

Claims

1. A lithium secondary battery comprising:

a positive electrode of which an active material is a lithium transition metal composite oxide;

a negative electrode of which an active material is a carbon material; and

a nonaqueous electrolyte composed of an organic solvent in which a lithium salt is dissolved, said non aqueous electrolyte containing at least one kind of conductive polymer-forming monomers which have an alkyl group and are electrochemically polymerizable on said positive electrode within a battery operation voltage, and at least one kind of film-forming agents which electrochemically decompose within said battery operation voltage to form films on a surface of said negative electrode.

2. A lithium secondary battery as claimed in claim 1, wherein said at least one kind of conductive polymer-forming monomers is added in the ratio of 0.1 to 5 volume %.

3. A lithium secondary battery as claimed in claim 2, wherein said at least one kind of conductive polymer-forming monomers is added in the ratio of 0.25 to 2 volume %.

4. A lithium secondary battery as claimed in claim 1, wherein said conductive polymer-forming monomers include at least one kind of derivatives of thiophene and derivatives of pyrrole, each having an alkyl group of which the carbon number is 4 to 10.

5. A lithium secondary battery as claimed in claim 4, wherein said conductive polymer-forming monomers include at least one kind of derivatives of pyrrole, having an alkyl group of which the carbon number is 4 to 10.

6. A lithium secondary battery as claimed in claim 4, wherein said conductive polymer-forming monomers include at least one kind of derivatives of thiophene, having an alkyl group of which the carbon number is 4 to 10.

7. A lithium secondary battery as claimed in claim 6, wherein said at least one kind of derivatives of thiophene is 3-hexyl thiophene.

8. A lithium secondary battery as claimed in claim 1, wherein said at least one kind of film-forming agents is added in the ratio of 0.1 to 5 volume %.

9. A lithium secondary battery as claimed in claim 8, wherein said at least one kind of film-forming agents is added in the ratio of 0.25 to 2 volume %.

10. A lithium secondary battery as claimed in claim 1, wherein said film-forming agents are at least one kind of methyl perfluorooctanate, methyl difluorobenzoate, propane sultone, 1,4-butane sultone and vinylene carbonate.

11. A lithium secondary battery as claimed in claim 10, wherein said film-forming agents include methyl perfluorooctanate.

12. A lithium secondary battery as claimed in claim 1, wherein said lithium transition metal composite oxide is a lithium nickel composite oxide having a basic composition of LiNiO₂ and a layered rock-salt structure.

13. A lithium secondary battery as claimed in claim 1, wherein said lithium transition metal composite oxide is a mixture of a lithium nickel composite oxide having a basic composition of LiNiO₂ and a layered rock-salt structure, and a lithium manganese composite oxide having a basic composition of LiMn₂O₄ and a spinel structure.

14. A lithium secondary battery as claimed in claim 1, wherein said organic solvent is a mixture of propylene carbonate, dimethyl carbonate and hexaetoxy tricyclo phosphazene.

15. A lithium secondary battery as claimed in claim 1, wherein said organic solvent is a mixture of propylene carbonate and ethylene carbonate.