Negative active material for a rechargeable lithium battery, a method of preparing the same, and a rechargeable lithium battery comprising the same
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 y O 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.
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 (1−y) M y O 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 cm 2 /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 −6 cm 2 /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.
9. 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.