Non-aqueous electrolyte and lithium secondary battery comprising same

• US 20040259002A1
• Filed: 04/02/2004
• Published: 12/23/2004
• Est. Priority Date: 04/03/2003
• Status: Active Grant

• Current Assignee: Panax Etec Co., Ltd. (DONGWHA ENTERPRISE Co., Ltd.), Samsung SDI Company Limited
• Original Assignee: Cheil Industries Incorporated, Samsung SDI Company Limited
• Inventors: Hwang, Sang-Moon, Kim, Hak-Soo, Kim, Jin-Sung, Kim, Jin-Hee, Paik, Meen-Seon
• Granted Patent: US 7,745,054 B2
• Time in Patent Office: Days
• US Class Current: 429/326
• 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 10/0567 characterised by the additives
• CPC Class Codes: H01M 10/0568 characterised by the solutes
• CPC Class Codes: H01M 10/0569 characterised by the solvents
• 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 2300/0037 Mixture of solvents
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

An electrolyte for a lithium secondary battery includes lithium salts, a non-aqueous organic solvent, and additive compounds, which initiates decomposition at 4V to 5V and show a constant current maintenance plateau region of more than or equal to 0.5V at measurement of LSV (linear sweep voltammetry). The additive compounds added to the electrolyte of the present invention decompose earlier than the organic solvent to form a conductive polymer layer on the surface of a positive electrode by increased electrochemical energy and heat at overcharge. The conductive polymer layer prevents decomposition of the organic solvent. Accordingly, the electrolyte inhibits gas generation caused by decomposition of the organic solvent during high temperature storage, and also improves safety of the battery during overcharge.

Claims

1. A non-aqueous electrolyte for a lithium secondary battery, comprising:

a lithium salt;

an organic solvent; and

an additive compound which initiates decomposition at between 4V and 5V and shows a constant current maintenance plateau region of at least 0.5V at measurement of LSV (linear sweep voltammetry).

2. The non-aqueous electrolyte for a lithium secondary battery according to claim 1, wherein the additive compound has a second constant current maintenance at a voltage of at least 6.5V.

3. The non-aqueous electrolyte for a lithium secondary battery according to claim 1, wherein the additive compound initiates decomposition at between 4.5V and 5V.

4. The non-aqueous electrolyte for a lithium secondary battery according to claim 1, wherein the electrolyte shows exothermic peaks of less than or equal to about 100°

C. at overcharge of more than 12V.

5. The non-aqueous electrolyte for a lithium secondary battery according to claim 1, wherein the additive compound is selected from the group consisting of bisphenol A, 2,5-dimethylfuran, 2,3-dichloro-1,4-naphthoquinone, and combinations thereof.

6. The non-aqueous electrolyte for a lithium secondary battery according to claim 1, wherein the additive compound is provided in an amount from 0.01 to 10 wt %, based on the total weight of electrolyte.

7. The non-aqueous electrolyte for a lithium secondary battery according to claim 6, wherein the additive compound is provided in an amount from 0.01 to 5 wt %, based on the total weight of electrolyte.

8. The non-aqueous electrolyte for a lithium secondary battery according to claim 7, wherein the additive compound is provided in an amount from 0.01 to 1 wt %, based on the total weight of electrolyte.

9. The non-aqueous electrolyte for a lithium secondary battery according to claim 8, wherein the additive compound is provided in an amount from 0.01 to 0.5 wt %, based on the total weight of electrolyte.

10. The non-aqueous electrolyte for a lithium secondary battery according to claim 1, wherein the additive compound forms a passivation layer on a surface of a positive electrode.

11. The non-aqueous electrolyte for a lithium secondary battery according to claim 1, wherein the lithium salt is selected from the group consisting of LiPF₆, LiBF₄, LiSbF₆, LiAsF₆, LiClO₄, LiCF₃SO₃, Li(CF₃SO₂)₂N, LiC₄F₉SO₃, LiSbF₆, LiAlO₄, LiAlCl₄, LiN(C_xF_2x+1SO₂)(C_yF_2y+1SO₂) wherein x and y are natural numbers, LiCl, LiI, and combinations thereof.

12. The non-aqueous electrolyte for a lithium secondary battery according to claim 11, wherein the lithium salt is provided at a concentration in the range of 0.6 to 2.0 M.

13. The non-aqueous electrolyte for a lithium secondary battery according to claim 1, wherein the non-aqueous organic solvent is selected from the group consisting of carbonates, esters, ethers, ketones, and combinations thereof.

14. The non-aqueous electrolyte for a lithium secondary battery according to claim 13, wherein the carbonate is selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methylethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), and mixtures thereof.

15. The non-aqueous electrolyte for a lithium secondary battery according to claim 13, wherein the carbonate comprises a mixed solvent of a cyclic carbonate and a chain carbonate.

16. The non-aqueous electrolyte for a lithium secondary battery according to claim 1, wherein the organic solvent comprises a mixed solvent of a carbonate solvent and an aromatic hydrocarbon solvent.

17. The non-aqueous electrolyte for a lithium secondary battery according to claim 16, wherein the aromatic hydrocarbon solvent is a compound of Formula (1):

18. The non-aqueous electrolyte for a lithium secondary battery according to claim 16, wherein the aromatic hydrocarbon solvent is selected from the group consisting of benzene, fluorobenzene, toluene, fluorotoluene, trifluorotoluene, chlorobenzene, nitrobenzene, xylene, and mixtures thereof.

19. The non-aqueous electrolyte for a lithium secondary battery according to claim 16, wherein the carbonate solvent and the aromatic hydrocarbon solvent are mixed in a volume ratio from 1:

1 to 30;

1.

20. The non-aqueous electrolyte for a lithium secondary battery according to claim 1, wherein the electrolyte further comprises an organic sulfone-based compound.

21. The non-aqueous electrolyte for a lithium secondary battery according to claim 20, wherein the organic sulfone-based compound is represented by the following formula (2):

22. The non-aqueous electrolyte for a lithium secondary battery according to claim 21, wherein R₂ and R₃ are independently selected from the group consisting of C₁ to C₄ alkyls, C₂ to C₄ alkenyls, C₆ to C₁₄ aryls, and C₃ to C₆ cycloalkyls.

23. The non-aqueous electrolyte for a lithium secondary battery according to claim 21, wherein one of R₂ and R₃ is selected from the group consisting of halogen-substituted alkyls, alkenyls, aryl group, and cycloalkyls.

24. The non-aqueous electrolyte for a lithium secondary battery according to claim 21, wherein one of R₂ and R₃ is an alkenyl.

25. The non-aqueous electrolyte for a lithium secondary battery according to claim 21, wherein the organic sulfone-based compound is provided in an amount from 0.01 to 5 wt % based on the total weight of electrolyte.

26. A non-aqueous electrolyte for a lithium secondary battery, comprising:

a lithium salt;

an organic solvent; and

bisphenol A as an additive compound.

27. A lithium secondary battery comprising:

a positive electrode including a material that reversibly intercalates/deintercalates lithium ions;

a negative electrode selected from the group consisting of lithium metal, a lithium-containing alloy, a material that reversibly forms a lithium-containing compound as a positive active material, a material that reversibly intercalates/deintercalates the lithium ions, and combinations thereof; and

a non-aqueous electrolyte wherein the non-aqueous electrolyte comprises;

a lithium salt;

an organic solvent; and

an additive compound which initiates decomposition at from 4V to 5V and shows a constant current maintenance plateau region of at least 0.5V at measurement of LSV (linear sweep voltammetry).

28. The lithium secondary battery according to claim 27, wherein the positive electrode is selected from the group consisting of lithium-nickel-based and lithium-nickel-manganese-based oxide.

29. The lithium secondary battery according to claim 27, wherein the lithium secondary battery is a lithium ion battery or lithium polymer battery.