Negative electrode active material, negative electrode comprising negative electrode active material, secondary battery comprising negative electrode, and method for preparing negative electrode active material
A negative electrode active material including: silicon-containing composite particles including (a) SiO x , wherein 0<x<2, (b) pores, and (c) a Mg compound or a Li compound; an outer carbon layer present on the surface of the silicon-containing composite particle; and an inner carbon layer present inside the pores, in which a BET specific surface area of the negative electrode active material is 3 m 2 /g to 15 m 2 /g, a negative electrode including the same, a secondary battery including the negative electrode and a method for preparing the negative electrode active material.
1 . A negative electrode active material comprising:
silicon-containing composite particles comprising (a) SiO x , wherein 0<x<2, (b) pores, and (c) a Mg compound or a Li compound;
an outer carbon layer present on a surface of the silicon-containing composite particles; and
an inner carbon layer present inside the pores,
wherein a pore size of the pores is 1 nm to 40 nm, and
wherein a BET specific surface area of the negative electrode active material is 3 m 2 /g to 15 m 2 /g.
2 . The negative electrode active material of claim 1 , wherein a Mg element is present in an amount of 0.1 wt % to 10 wt % based on a total 100 wt % of the silicon-containing composite particles.
3 . The negative electrode active material of claim 1 , wherein a Li element is present in an amount of 0.1 wt % to 10 wt % based on a total 100 wt % of the silicon-containing composite particles.
4 . The negative electrode active material of claim 1 , wherein a total wt % of the outer carbon layer and the inner carbon layer is 5 wt % to 40 wt % based on a total 100 wt % of the negative electrode active material.
5 . The negative electrode active material of claim 1 , wherein the outer carbon layer is present in an amount of 1 wt % to 10 wt % based on a total 100 wt % of the negative electrode active material.
6 . The negative electrode active material of claim 1 , wherein the inner carbon layer is present in an amount of 4 wt % to 35 wt % based on a total 100 wt % of the negative electrode active material.
7 . The negative electrode active material of claim 1 , wherein the negative electrode active material has an average particle diameter (D 50 ) of 2 μm to 15 μm.
8 . A method for preparing the negative electrode active material according to claim 1 , the method comprising:
forming silicon-containing composite particles comprising pores from preliminary silicon-containing composite particles comprising SiO x , where 0<x<2, and a Mg compound or a Li compound;
forming a preliminary negative electrode active material comprising an outer carbon layer and an inner carbon layer by disposing a carbonaceous precursor on the silicon-containing composite particles, and then subjecting the carbonaceous precursor to a first heat treatment; and
subjecting the preliminary negative electrode active material to a second heat treatment.
9 . The method of claim 8 , wherein the forming of the silicon-containing composite particles comprising pores from preliminary silicon-containing composite particles comprising SiO x , where 0<x<2, and a Mg compound or a Li compound comprises etching the preliminary silicon-containing particles using an acid or a base.
10 . The method of claim 8 , wherein the first heat treatment is performed at a temperature of 600° C. to 1100° C.
11 . The method of claim 8 , wherein the second heat treatment is performed at a temperature of 600° C. to 1100° C.
12 . A negative electrode comprising the negative electrode active material according to claim 1 .
13 . A secondary battery comprising the negative electrode of claim 12 .