Cathode active material and lithium secondary battery containing the same

摘要

Disclosed herein is a cathode active material for secondary batteries and a secondary battery including the same, the cathode active material including lithium manganese oxide (A) having a spinel crystal structure and at least two types of lithium nickel-manganese-cobalt composite oxides (B) containing Ni, Mn, and Co as transition metals, wherein the lithium nickel-manganese-cobalt composite oxides (B) are different from each other in terms of at least one selected from the group consisting of elemental composition, particle diameter, and density.

主权项

1. A cathode active material for secondary batteries, the cathode active material being a mixture comprising at least one type of lithium manganese oxide (A) having a spinel crystal structure and at least two types of lithium nickel-manganese-cobalt composite oxides (B) containing Ni, Mn, and Co as transition metals,
wherein the lithium nickel-manganese-cobalt composite oxides (B) are different from each other in terms of at least one selected from the group consisting of particle diameter, and density, wherein the lithium manganese oxide has a spinel crystal structure and has an elemental composition represented by Formula (1) and the lithium nickel-manganese-cobalt composite oxides are selected from compounds having an elemental composition represented by Formula (2):
Li1+xMn2−yMyO4  (1)Li1+zNiaMnbCo1−(ab)O2  (2) where 0≦x≦0.2 and 0≦y≦1, where M is at least one element selected from the group consisting of Al, Mg, Ni, Co, Fe, Cr, V, Ti, Cu, B, Ca, Zn, Zr, Nb, Mo, Sr, Sb, W and Bi, and where 0≦z≦0.1, 0.2≦a≦0.7, 0.2≦b≦0.7 and a+b<1, wherein the lithium nickel-manganese-cobalt composite oxides (B) comprise two types of oxides having the same elemental composition and different particle diameters, wherein the lithium nickel-manganese-cobalt composite oxides (B) comprising a first oxide (B1) and a second oxide (B2) have an average particle diameter in a range from 3 to 10 μm and an average particle diameter of the first oxide (B1) is 10 to 70% of an average particle diameter of the second oxide (B2), and wherein the mixture ratio of the first oxide (B1) and the second oxide (B2) is 50:50 by weight.