Positive electrode active material, method of manufacturing the positive electrode active material, and lithium battery employing the positive electrode active material
In one aspect, a positive electrode active material is provided, a method of manufacturing the positive electrode active material, and a lithium battery employing the positive electrode active material. The positive electrode active material may have high thermal stability and low capacity deterioration despite repetitive charging and discharging.
1. A positive electrode active material comprising:
a core having a total average composition and a surface, wherein the a total average composition of the core is represented by Formula 2 and the composition of the surface is represented by Formula 2′; and
a complex coating layer formed on the surface and comprising titanium dioxide (TiO 2 ) and lithium titanium oxide (LiTi x O y ),
wherein 1≦x≦2 and 2.5≦y≦3,
Li a Ni 1-b-c Co b M c A p [Formula 2]
wherein a, b, c, and p each respectively satisfy 0.95≦a≦1.05, 0<b≦0.5, 0<c≦0.5, p=2, M is manganese (Mn), and A is oxygen (O), and
Li a′ Ni 1-b′-c′ Co b′ Mn c′ O 2 [Formula 2′]
wherein a′, b′, and c′ each respectively satisfy 1.08≦a′≦1.35, 0<b′≦0.5, 0<c′≦0.5, and a′>a.
2. The positive electrode active material of claim 1 , wherein is manganese the total average composition of the core is represented by Li 1.00 Ni 0.5 Co 0.2 Mn 0.3 O 2 .
3. The positive electrode active material of claim 2 , wherein the composition of the surface is represented by Li 1.09 Ni 0.53 Co 0.19 Mn 0.28 O 2 .
4. The positive electrode active material of claim 1 , wherein the complex coating layer has a structure in which LiTi x O y crystals are distributed in a TiO 2 matrix.
5. The positive electrode active material of claim 4 , wherein, in the complex coating layer, the LiTi x O y crystals in the TiO 2 matrix are adjacent to the surface of the core.
6. The positive electrode active material of claim 1 , wherein a total amount of TiO 2 and LiTi x O y is from about 0.01 to about 50 wt % based on a total weight of the positive electrode active material.
7. The positive electrode active material of claim 1 , wherein a total amount of TiO 2 and LiTi x O y is from about 0.01 to about 20 wt % based on a total weight of the positive electrode active material.
8. The positive electrode active material of claim 1 , wherein a total amount of TiO 2 and LiTi x O y is from about 0.01 to about 10 wt % based on a total weight of the positive electrode active material.
9. An electrode for a lithium battery, the electrode comprising the positive electrode active material of claim 1 .
10. The electrode for a lithium battery of claim 9 , wherein the composition of the surface is represented by Li 1.09 Ni 0.53 Co 0.19 Mn 0.28 O 2 .
11. A lithium battery comprising a positive electrode that comprises the positive electrode active material of claim 1 .
12. The electrode for a lithium battery of claim 11 , wherein the composition of the surface is represented by Li 1.09 Ni 0.53 Co 0.19 Mn 0.28 O 2 .
13. The positive electrode active material of claim 11 , wherein a total amount of TiO 2 and LiTi x O y is from about 0.01 to about 50 wt % based on a total weight of the positive electrode active material.