Patent ID: 8758941

Claim:
A lithium ion secondary battery comprising: a positive electrode, a negative electrode, a separator located between the cathode and the anode, and a non-aqueous electrolyte, wherein the positive electrode has mixture of at least three kinds of transition metal oxides as a positive electrode active substance, said transition metal oxide represented by Li x Ni a Mn b Co c M d O 2 , in which 0.2≦x≦1.2, 0.2≦a≦0.9, 0.05≦b≦0.5, 0.05≦c≦0.5, 0≦d≦0.1, and a+b+c+d=1.0, and each transition metal oxide having different nickel contents, wherein M is Al or Ti or combinations thereof when d>0, wherein said transition metal oxides comprise first, second and third transition metal oxide, wherein the first transition metal oxide is represented by formula Li x1 Ni a1 Mn b1 Co c1 M d1 O 2 , in which 0.2≦x1≦1.2, 0.7≦a1≦0.9, 0.05≦b1≦0.25, 0.05≦c1≦0.25, 0≦d1≦0.1, and a1+b1+c1+d1=1.0, the second transition metal oxide is represented by formula Li x2 Ni a2 Mn b2 Co c2 M d2 O 2 , in which 0.2≦x2≦1.2, 0.55≦a2≦0.8, 0.05≦b2≦0.4, 0.05≦c2≦0.4, 0≦d2≦0.1, and a2+b2+c2+d2=1.0, the third transition metal oxide is represented by formula Li x3 Ni a3 Mn b3 Co c3 M d3 O 2 , in which 0.2≦x3≦1.2, 0.2≦a3≦0.65, 0.05≦b3≦0.5, 0.05≦c3≦0.5, 0≦d3≦0.1, a3+b3+c3+d3=1.0, and in which a3<a2<a1.