Negative electrode active material, preparation method thereof, and negative electrode and secondary battery including same
The present invention relates to a negative electrode active material including silicon-based oxide particles and a metal distributed on a surface, inside, or on the surface of and the inside the silicon-based oxide particles, wherein compressive fracture strength measured at a pressure of 100 mN is 170 MPa to 380 MPa, and the silicon-based oxide particles contain Si crystal grains having a crystal grain size of 3 nm to 20 nm.
1. A negative electrode active material comprising:
silicon-based oxide particles; and
a metal distributed on a surface, inside, or on the surface of and the inside the silicon-based oxide particles,
wherein compressive fracture strength measured at a pressure of 100 mN is 170 MPa to 380 MPa, and
the silicon-based oxide particles contain Si crystal grains having a crystal grain size of 3 nm to 20 nm.
2. The negative electrode active material of claim 1 , wherein the metal is included in the negative electrode active material in an amount of 0.1 wt % to 25 wt % with respect to 100 wt % of the negative electrode active material.
3. The negative electrode active material of claim 1 , wherein the metal is at least one selected from the group consisting of Li, Mg, and Al.
4. The negative electrode active material of claim 1 , wherein the metal is Mg, and the Mg is present in the negative electrode active material in a form of at least one magnesium silicate selected from the group consisting of MgSiO 3 and Mg 2 SiO 4 .
5. The negative electrode active material of claim 4 , wherein:
Mg is present in the negative electrode active material in the forms of MgSiO 3 and Mg 2 SiO 4 ;
MgSiO 3 is included in the negative electrode active material in an amount of 5 wt % to 25 wt % with respect to 100 wt % of the negative electrode active material; and
Mg 2 SiO 4 is included in the negative electrode active material in an amount of 3 wt % to 30 wt % with respect to 100 wt % of the negative electrode active material.
6. The negative electrode active material of claim 4 , wherein Mg is present in the negative electrode active material in the forms of MgSiO 3 and Mg 2 SiO 4 , and a weight ratio of Mg 2 SiO 4 to MgSiO 3 is 0.3 to 1.2.
7. The negative electrode active material of claim 1 , wherein a Brunauer Emmett Teller (BET) specific surface area of the negative electrode active material is 0.5 m 2 /g to 7.5 m 2 /g.
8. The negative electrode active material of claim 1 , wherein the silicon-based oxide particles include a compound represented by Formula 1 below:
SiO x [Formula 1]
wherein in Formula 1, 0<x<2.
9. The negative electrode active material of claim 1 , further comprising a carbon coating layer formed on the silicon-based oxide particles.
10. A method for preparing the negative electrode active material according to claim 1 , the method comprising:
mixing silicon-based oxide particles and a metal-containing material; and
heat-treating the mixture at 1,050° C. to 1,350° C.,
wherein the silicon-based oxide particles and the metal-containing material are subjected to solid mixing.
11. The method of claim 10 , wherein the metal-containing material is at least one selected from the group consisting of a metal and a metal oxide.
12. The method of claim 10 , wherein the heat-treatment is performed for 1 hour to 8 hours.
13. A negative electrode comprising:
a negative electrode current collector; and
a negative electrode active material layer formed on the negative electrode current collector, wherein
the negative electrode active material layer includes a negative electrode material containing the negative electrode active material according to claim 1 .
14. A secondary battery comprising:
the negative electrode according to claim 13 ;
a positive electrode opposing the negative electrode;
a separator interposed between the positive electrode and the negative electrode; and
an electrolyte.