Silicon-based negative active material, preparing method of preparing same and rechargeable lithium battery including same

1. A silicon-based negative active material, comprising:

a core comprising silicon oxide represented by SiO x (0<x<2); and

a coating layer comprising metal oxide,

wherein:

the metal of the metal oxide comprises at least one selected from aluminum (Al), titanium (Ti), cobalt (Co), magnesium (Mg), calcium (Ca), potassium (K), sodium (Na), boron (B), strontium (Sr), barium (Ba), manganese (Mn), nickel (Ni), vanadium (V), iron (Fe), copper (Cu), phosphorus (P), scandium (Sc), zirconium (Zr), niobium (Nb), chromium (Cr), and molybdenum (Mo),

the core has a concentration gradient where an atom % concentration of a silicon (Si) element decreases according to increase of a depth from a surface contacting the coating layer to the center of the core, and an atom % concentration of an oxygen (O) element increases according to increase of the depth from the surface contacting the coating layer to the center of the core, and

the depth from the surface contacting the coating layer where a concentration of the silicon (Si) element is about 55 atom % corresponds to about 2% to about 20% of a diameter of the core.

2. The silicon-based negative active material of claim 1 , wherein in the coating layer, in an integration of an atom % concentration of the silicon (Si) element according to the depth from the surface contacting the coating layer to the center of the core, an integral value of the atom % concentration of the silicon (Si) element from the depth of 0 to the depth where the concentration of the silicon (Si) element is about 55 atom % is in a range from about 5000 nm atom % to about 40000 nm atom %.

3. The silicon-based negative active material of claim 1 , wherein the depth from the surface contacting the coating layer where the concentration of the silicon (Si) element is about 55 atom % corresponds to about 100 nm to about 1000 nm.

4. The silicon-based negative active material of claim 1 , wherein the core comprises crystalline silicon (Si) and non-crystalline silicon oxide.

5. The silicon-based negative active material of claim 4 , wherein an amount of Si is about 50 wt % to about 70 wt % based on 100 wt % of the core, and the amount of Si includes both the amount of Si in the crystalline Si and the amount of Si in the non-crystalline silicon oxide.

6. The silicon-based negative active material of claim 4 , wherein a concentration of the crystalline silicon (Si) increases toward the surface contacting the coating layer.

7. The silicon-based negative active material of claim 1 , wherein the core comprises SiO x , and wherein 0.5<x<1.5 and x indicates a content ratio of the silicon (Si) element to the oxygen (O) element.

8. The silicon-based negative active material of claim 1 , wherein the core has an average particle diameter of about 0.1 μm to about 100 μm.

9. The silicon-based negative active material of claim 1 , wherein the silicon-based negative active material has a specific surface area of about 10 m 2 /g to about 500 m 2 /g.

10. The silicon-based negative active material of claim 1 , wherein a pore is included in at least one part of the surface of contact between the core and coating layer.

11. The silicon-based negative active material of claim 1 , wherein the coating layer has a thickness of about 5 nm to about 100 nm.

12. The silicon-based negative active material of claim 1 , wherein a weight ratio of the core to the coating layer is in a range from about 99.9:0.1 to about 95:5.

13. The silicon-based negative active material of claim 1 , wherein the metal oxide is Ti oxide, and the Ti oxide is TiO 2 , TiO x (0<x<2), or a combination thereof.

14. The silicon-based negative active material of claim 1 , wherein the silicon-based negative active material further comprises an outermost coating layer comprising a carbon-based material.

15. A rechargeable lithium battery, comprising:

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

a positive electrode comprising a positive active material for intercalating and deintercalating lithium; and

a non-aqueous electrolyte.

16. The rechargeable lithium battery of claim 15 , wherein in the coating layer, in an integration of an atom % concentration of the silicon (Si) element according to the depth from the surface contacting the coating layer to the center of the core, an integral value of the atom % concentration of the silicon (Si) element from the depth of 0 to the depth where the concentration of the silicon (Si) element is about 55 atom % is in a range from about 5000 nm atom % to about 40000 nm atom %.

17. The rechargeable lithium battery of claim 15 , wherein the depth from the surface contacting the coating layer where the concentration of the silicon (Si) element is about 55 atom % corresponds to about 100 nm to about 1000 nm.