Negative electrode active material for lithium secondary battery and method for preparing the same
A negative electrode active material including a core, an intermediate layer on a surface of the core, and a shell layer on a surface of the intermediate layer, wherein the core includes a silicon oxide of SiO x (0<x<2); the intermediate layer includes a lithium silicate, the shell layer includes lithium fluoride (LiF) and the intermediate layer is present in an amount of 5 wt %-15 wt % based on a total weight of the negative electrode active material. Also, a method for preparing the negative electrode active material, and a negative electrode and lithium secondary battery including the same. The negative electrode active material provides excellent initial efficiency and life characteristics.
1. A negative electrode active material, comprising:
a core;
an intermediate layer on a surface of said core; and
a shell layer on a surface of said intermediate layer,
wherein the core comprises a silicon oxide of formula SiO x wherein 0<X<2;
the intermediate layer comprises a lithium silicate;
the shell comprises lithium fluoride (LiF); and
the intermediate layer is present in an amount of 5 wt %-15 wt % based on a total weight of the negative electrode active material.
2. The negative electrode active material according to claim 1 , wherein the silicon oxide comprises a nanocomposite structure in which Si is present in combination with SiO 2 .
3. The negative electrode active material according to claim 1 , wherein the lithium silicate comprises lithium silicate represented by the formula of Li a Si b O c , wherein 2<a≤4, 0<b≤2, 2<c≤5 and SiO y , wherein 0<y<2.
4. The negative electrode active material according to claim 3 , wherein the lithium silicate comprises Li 2 Si 2 O 5 , Li 2 SiO 3 and Li 4 SiO 4 .
5. The negative electrode active material according to claim 1 , wherein the intermediate layer has a thickness of 1 nm-1,000 nm.
6. The negative electrode active material according to claim 1 , wherein the shell layer is present in an amount of 0.1 wt %-3 wt % based on the total weight of the negative electrode active material.
7. The negative electrode active material according to claim 1 , wherein the shell layer has a thickness of 10 nm-200 nm.
8. The negative electrode active material according to claim 1 , which further comprises a carbon coating layer on a surface of the shell layer.
9. A negative electrode comprising a current collector and an electrode layer formed on at least one surface of the current collector, wherein the electrode layer comprises the negative electrode active material as defined in claim 1 .
10. A lithium secondary battery comprising the negative electrode as defined in claim 9 .