Negative electrode active material, negative electrode including the negative electrode active material, and secondary battery including the negative electrode
A negative electrode active material which includes a core including SiO x (0<x<2), a shell disposed on the core and includes lithium silicate, and a coating layer disposed on the shell and includes carbon nanotubes. Also, a method of preparing a negative electrode active material as well as a negative electrode and a battery including the same.
1 . A method of preparing a negative electrode active material, the method comprising:
mixing SiO x particles and Li 2 CO 3 , wherein 0<x<2; and
performing a heat treatment on the mixed SiO x particles and Li 2 CO 3 with a catalyst in a H 2 gas atmosphere to form lithium silicate and carbon nanotubes in the negative electrode active material,
wherein the lithium silicate and the carbon nanotubes are simultaneously formed from the Li 2 CO 3 in the heat treatment step.
2 . The method of claim 1 , wherein a weight ratio of the SiO x particles to the Li 2 CO 3 is in a range of 1:0.111 to 1:0.667.
3 . The method of claim 1 , wherein the heat treatment is performed at a temperature range of 800° C. to 1,200° C.
4 . The method of claim 1 , wherein the catalyst comprises at least one oxide selected from the group consisting of iron (Fe) and calcium (Ca).
5 . The method of claim 1 , wherein the H 2 gas atmosphere is formed by introducing H 2 into the mixed SiO x particles and Li 2 CO 3 at a flow rate of 500 sccm to 1,000 sccm for a time period of 30 minutes to 2 hours.
6 . The method of claim 1 , further comprising:
performing an acid treatment on the heat-treated SiO x particles and Li 2 CO 3 after performing the heat treatment.
7 . The method of claim 1 , wherein the carbon nanotubes are formed by reaction of H 2 gas in the H 2 gas atmosphere with CO 2 generated during the formation of the lithium silicate.
8 . The method of claim 1 , wherein the lithium silicate comprises at least one of Li 2 SiO 3 and Li 2 Si 2 O 5 .
9 . The method of claim 1 , wherein the catalyst comprises at least one oxide selected from the group consisting of FeO and CaO.
10 . The method of claim 1 , wherein 0<x<1.
11 . The method of claim 1 , wherein 0.3≤x≤0.6.