Negative electrode active material and lithium secondary battery comprising same
Provided is a negative active material and a lithium secondary battery including the negative active material. The negative active material for a secondary battery includes silicon particles, wherein circularities of the particles are determined by equation 1 below, and the circularities are 0.5 or greater and 0.9 or less, Circularity=2( pi×A ) 1/2 /P [Equation 1] where A denotes a projected area of the silicon particle that is two-dimensionally projected, and P denotes a circumferential length of the silicon particle that is two-dimensionally projected.
1. A negative active material for a secondary battery, the negative active material comprising silicon particles,
wherein an average diameter of the silicon particles is in a range from 30 nm to 300 nm, and
wherein circularities of the silicon particles are determined by Equation 1 below, and the circularities are 0.5 or greater and 0.9 or less,
Circularity=2( pi×A ) 1/2 /P [Equation 1]
where A denotes a projected area of a silicon particle that is two-dimensionally projected, and P denotes a circumferential length of the silicon particle that is two-dimensionally projected.
2. The negative active material of claim 1 , wherein the silicon particles comprise solid particles.
3. The negative active material of claim 1 , wherein the circularities of the silicon particles are 0.6 or greater and 0.8 or less.
4. The negative active material of claim 1 , wherein an area of a (110) surface of each of the silicon particles is greater than an area of a (100) surface and an area of a (111) surface.
5. The negative active material of claim 1 , wherein the silicon particles comprise a silicon oxide layer formed as a shell on the silicon particles.
6. The negative active material of claim 5 , wherein the silicon particles comprise a silicon carbide layer formed as a shell on the silicon oxide layer.
7. The negative active material of claim 5 , wherein a thickness of the silicon oxide layer is in a range of 0.5 nm to 20 nm.
8. The negative active material of claim 5 , wherein the silicon oxide layer is chemical silicon oxide that is artificially grown using a solvent comprising oxygen.
9. The negative active material of claim 8 , wherein the solvent comprising oxygen is alcohol, distilled water, or a peroxide compound.
10. The negative active material of claim 1 , further comprising a conductive layer formed on the silicon particles.
11. The negative active material of claim 10 , wherein the conductive layer comprises an amorphous carbon layer or conductive metal oxide particles.
12. The negative active material of claim 1 , wherein the silicon particles have a purity of 99% or greater.
13. A lithium secondary battery comprising the negative active material of claim 1 .
14. The negative active material of claim 1 , wherein the silicon particles have irregular shapes.
15. The negative active material of claim 1 , wherein a dominant external surface of each of the silicon particles is a {110} surface.