Negative electrode active material for secondary battery and method for manufacturing same
Provided is an anode active material for a secondary battery and a method of fabricating the anode active material. A silicon-based active material composite according to an embodiment of the inventive concept includes silicon and silicon oxide obtained by oxidizing at least a part of the silicon, and an amount of oxygen with respect to a total weight of the silicon and the silicon oxide is restricted to 9 wt % to 20 wt %.
1. A method of fabricating a silicon-based active material, the method comprising:
providing silicon particles; and
oxidizing the silicon particles to form a silicon-based active material comprising particles with a silicon core and a shell of silicon oxide surrounding the core,
wherein the shell of silicon oxide is obtained by oxidizing at least a part of the silicon particles,
wherein an amount of oxygen with respect to a total weight of the silicon core and the shell of silicon oxide is restricted to 9 wt % to 20 wt %,
wherein the oxidizing of the silicon particles is performed by chemically oxidizing the silicon particles in a liquid solvent comprising oxygen,
wherein the silicon particles are miniaturized through a grinding process or a pulverizing process performed on a slurry comprising the silicon particles and the liquid solvent comprising oxygen,
wherein the chemically oxidizing of silicon particles is induced by at least one of compressive stress and shearing stress induced from the grinding process or the pulverizing process at a same time as the silicon particles are miniaturized.
2. The method of claim 1 , wherein the liquid solvent containing oxygen comprises methanol, isopropyl alcohol (IPA), hydrogen peroxide (H 2 O 2 ), water, or a mixed solvent including two or more thereof.
3. The method of claim 1 , wherein the oxidizing of the silicon particles is performed by implanting oxygen ions into the silicon particles.
4. The method of claim 3 , further comprising performing a thermal treatment at a low temperature of 50° C. to 200° C. for combining a silicon matrix and implanted oxygen while excluding a possibility of thermal oxidation of the silicon.
5. The method of claim 1 , wherein the shell of silicon oxide has a thickness in a range of 2 nm to 30 nm.
6. The method of claim 1 , wherein the particles of the silicon-based active material have an average diameter in a range of 30 nm to 300 nm.
7. The method of claim 1 , further comprising forming a conductive layer on an outermost portion of the particles of the silicon-based active material.
8. The method of claim 7 , wherein the conductive layer comprises a carbon-based conductive layer.
9. The method of claim 7 , wherein the conductive layer comprises an amorphous carbon layer.
10. The method of claim 7 , wherein the conductive layer comprises a crystalline carbon layer.
11. The method of claim 7 , wherein the conductive layer comprises SP 2 carbon and SP 3 carbon, wherein the mole fraction of SP 2 carbon is greater than the mole fraction of SP 3 carbon.
12. The method of claim 7 , wherein the conductive layer comprises conductive metal oxide particles.
13. The method of claim 1 , further comprising a step of forming secondary particles that are an agglomerate of the particles of the silicon-based active material.