Negative electrode active material for lithium secondary battery and method of preparing the same
The present specification relates to a negative electrode active material which includes a silicon-based composite represented by SiO a (0≤a<1), and a carbon coating layer distributed on a surface of the silicon-based composite, and which has a bimodal pore structure including nanopores and mesopores. In a lithium secondary battery including the negative electrode active material, an oxygen content in the silicon-based composite can be controlled to improve initial efficiency and capacity characteristics, and a specific surface area can also be controlled, and thus a side reaction with electrolyte can be reduced.
1. A negative electrode active material, consisting of:
particles represented by SiO a (0<a<1), wherein in the particles, a ratio of crystalline silicon and crystalline silica contained therein is expressed as 1−(a/2):(a/2), and wherein the particles represented by SiO a (0<a<1) consist of crystalline silicon and crystalline silica, and no amorphous silicon is present; and
wherein each particle has a carbon coating layer distributed on a surface of each particle,
wherein each particle has a bimodal pore structure inside each particle including mesopores and macropores,
wherein a specific surface area of the negative electrode active material is in a range of 1 m 2 /g to 20 m 2 /g, and
wherein each particle has the bimodal pore structure formed uniformly from an inner central portion to a surface portion of each particle.
2. The negative electrode active material according to claim 1 , wherein a diameter of the mesopores is in a range of 2 nm to 50 nm.
3. The negative electrode active material according to claim 1 , wherein a diameter of the macropores is in a range of 50 nm to 700 nm.
4. The negative electrode active material according to claim 1 , wherein a thickness of the carbon coating layer is in a range of 0.003 μm to 3.0 μm.
5. A secondary battery comprising the negative active material of claim 1 .