Negative active material for a rechargeable lithium battery, a method of preparing the same, and a rechargeable lithium battery comprising the same

• US 20050186475A1
• Filed: 02/24/2005
• Published: 08/25/2005
• Est. Priority Date: 02/25/2004
• Status: Active Grant

• Current Assignee: Samsung SDI Company Limited
• Original Assignee: Samsung SDI Company Limited
• Inventors: Lee, Sang-Min, Kim, Sung-Soo, Jeong, Goo-Jin, Nitta, Yoshiaki
• Granted Patent: US 7,432,015 B2
• Time in Patent Office: Days
• US Class Current: 429/231.600
• CPC Class Codes: C01B 33/24 Alkaline-earth metal silicates
• 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 10/054 Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium
• CPC Class Codes: H01M 2004/021 Physical characteristics, e.g. porosity, surface area
• 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 4/131 Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
• CPC Class Codes: H01M 4/133 Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
• CPC Class Codes: H01M 4/1391 of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
• CPC Class Codes: H01M 4/1393 of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
• CPC Class Codes: H01M 4/364 as mixtures
• 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

Abstract

The negative active material for a rechargeable lithium battery of the present invention includes a carbonaceous material and a silicon-based compound represented by Formula 1:
Si_(1-y)M_yO_1+x  (1) where 0<y<1, −0.5≦x≦0.5, and M is selected from the group consisting of Mg, Ca, and mixtures thereof.

Claims

1. A negative active material for a lithium secondary battery, comprising:

a carbonaceous material and a silicon-based compound represented by the following formula;

Si<sub>(1−

y)</sub>M_yO_1+x

where 0<

y<

1, −

0.5≦

x≦

0.5 and M is selected from the group consisting of Mg, Ca, and mixtures thereof.

2. The negative active material for a lithium secondary battery according to claim 1, wherein the negative active material has an amorphorization degree of 70% or more, and a diffusion rate of Li measured by GITT (Galvanostatic Intermittent Titration Technique) of 10⁻

8 cm²/sec or more.

3. The negative active material for a lithium secondary battery according to claim 1, wherein the negative active material has an amorphorization degree of between 70% and 99%, and a diffusion rate of Li measured by GITT (Galvanostatic Intermittent Titration Technique) of between 10⁻

8 and 10<sup>−

6</sup> cm²/sec.

4. The negative active material for a lithium secondary battery according to claim 1, wherein y is between 0 and 0.5, and x is between −

0.2 and 0.2.

5. The negative active material for a lithium secondary battery according to claim 1, wherein the carbonaceous material is selected from crystalline carbon and amorphous carbon.

6. The negative active material for a lithium secondary battery according to claim 1, wherein the silicon-based compound and the carbonaceous material are mixed in a weight ratio of between 95:

5 and 50;

50.

7. The negative active material for a lithium secondary battery according to claim 1, wherein the carbonaceous material is coated on the surface of the silicon-based compound.

8. The negative active material for a lithium secondary battery according to claim 1, wherein the negative active material is a mixture of the silicon-based compound and the carbonaceous material.

32. A lithium secondary battery comprising:

a negative electrode comprising the negative active material according to claim 1;

a positive electrode comprising a positive active material capable of reversibly intercalating/deintercalating the lithium; and

an electrolyte.

9. A method of preparing a negative active material for a lithium secondary battery comprising:

mixing SiO₂, Si, and a compound including Mg, Ca, or mixtures thereof;

heating the mixture to provide a silicon-based compound represented by the formula;

Si<sub>(1−

y)</sub>M_yO_1+x

where 0<

y<

1, −

0.5≦

x≦

0.5, and M is selected from the group consisting of Mg, Ca, and mixtures thereof;

quenching the heated silicon-based compound; and

coating the quenched silicon-based compound with a carbonaceous material.

10. The method of preparing a negative active material for a lithium secondary battery according to claim 9, wherein the SiO₂ and Si are mixed in a molar ratio of between 1:

1 and 1;

3.

11. The method of preparing a negative active material for a lithium secondary battery according to claim 9, wherein the compound including Mg, Ca or mixtures thereof is a glass network precursor.

12. The method of preparing a negative active material for a lithium secondary battery according to claim 9, wherein the compound including Mg, Ca or mixtures thereof is selected from the group consisting of MgO, CaO, and mixtures thereof.

13. The method of preparing a negative active material for a lithium secondary battery according to claim 9, wherein the compound including Mg, Ca or mixtures thereof is added at between 5 and 90 parts by weight-based on 100 parts by weight of the mixture of SiO₂ and Si.

14. The method of preparing a negative active material for a lithium secondary battery according to claim 9, wherein the heating is carried out at a temperature between 600 and 1000°

C.

15. The method of preparing a negative active material for a lithium secondary battery according to claim 14, wherein the heating is carried out at a temperature between 800 and 1000°

C.

16. The method of preparing a negative active material for a lithium secondary battery according to claim 9, wherein y is between 0 and 0.5, and x is between −

0.2 and 0.2.

17. The method of preparing a negative active material for a lithium secondary battery according to claim 9, wherein the quenching is performed by a melt-spinning technique.

18. The method of preparing a negative active material for a lithium secondary battery according to claim 9, wherein quenching is performed at a rate of between 102 and 107 K/sec.

19. The method of preparing a negative active material for a lithium secondary battery according to claim 9, wherein the carbonaceous material is selected from crystalline carbon or amorphous carbon.

20. A method of preparing a negative active material for a lithium secondary battery, comprising:

mixing SiO₂, Si, and a compound including Mg, Ca, or a mixture thereof;

heating the mixture to provide a silicon-based compound represented by the formula;

Si<sub>(1−

y)</sub>M_yO_1+x

where 0<

y<

1, −

0.5≦

x≦

0.5, and M is selected from the group consisting of Mg, Ca, and mixtures thereof;

quenching the heated silicon-based compound; and

mixing the quenched silicon-based compound and a carbonaceous material.

21. The method of preparing a negative active material for a lithium secondary battery according to claim 20, wherein the SiO₂ and Si are mixed in a molar ratio of between 1:

1 and 1;

3.

22. The method of preparing a negative active material for a lithium secondary battery according to claim 20, wherein compound including Mg, Ca, or mixtures thereof is a glass network precursor.

23. The method of preparing a negative active material for a lithium secondary battery according to claim 20, wherein the compound including Mg, Ca, or mixtures thereof is selected from the group consisting of MgO, CaO, and mixtures thereof.

24. The method of preparing a negative active material for a lithium secondary battery according to claim 20, wherein the compound including Mg, Ca, or mixtures thereof is added at between 5 and 90 parts by weight based on 100 parts by weight of the mixture of SiO₂ and Si.

25. The method of preparing a negative active material for a lithium secondary battery according to claim 20, wherein the heating is carried out at a temperature between 600 and 1000°

C.

26. The method of preparing a negative active material for a lithium secondary battery according to claim 25, wherein the heating is carried out at a temperature between 800 and 1000°

C.

27. The method of preparing a negative active material for a lithium secondary battery according to claim 20, wherein y is between 0 and 0.5, and x is between −

0.2 and 0.2.

28. The method of preparing a negative active material for a lithium secondary battery according to claim 20, wherein the quenching is performed by a melt-spinning technique.

29. The method of preparing a negative active material for a lithium secondary battery according to claim 20, wherein the quenching is performed at a rate of between 10² and 10⁷ K/sec.

30. The method of preparing a negative active material for a lithium secondary battery according to claim 20, wherein the carbonaceous material is selected from crystalline carbon and amorphous carbon.

31. The method of preparing a negative active material for a lithium secondary battery according to claim 20, wherein the silicon-based compound and the carbonaceous material are mixed in a weight ratio of 95:

5 to 50;

50.