Non-aqueous electrolyte secondary battery
A non-aqueous electrolyte secondary battery uses as its positive electrode active material a mixture of a first lithium-containing transition metal oxide containing nickel and manganese as transition metals and having a crystal structure belonging to the space group R3m and a second lithium-containing transition metal oxide containing nickel, cobalt, and manganese as transition metals and having a crystal structure belonging to the space group R3m, or a mixture of the first lithium-containing transition metal oxide and a lithium cobalt oxide. The first lithium-containing transition metal oxide is Li a Ni x Mn y O 2 wherein 1≦a≦1.5, 0.5≦x+y≦1, 0<x<1, and 0<y<1. The second lithium-containing transition metal oxide is Li b Ni p Mn q Co r O 2 wherein 1≦b≦1.5, 0.5≦p+q+r≦1, 0<p<1, 0<q<1, and 0<r<1.
1. A non-aqueous electrolyte secondary battery comprising:
a positive electrode comprising a positive electrode active material;
a negative electrode comprising a negative electrode active material; and
a non-aqueous electrolyte having lithium ion conductivity,
wherein the positive electrode active material consists of a mixture of a first lithium-containing transition metal oxide containing nickel and manganese as transition metals and having a crystal structure belonging to the space group R3m, the first lithium-containing transition metal oxide being represented by the formula Li e Ni x Mn y O, wherein 1≦a≦1.5, 0.5≦x+y≦1, 0<x<1, and 0<y<1, and a second lithium-containing transition metal oxide containing nickel, cobalt, and manganese as transition metals and having a crystal structure belonging to the space group R3m, the second lithium-containing transition metal oxide being represented by the formula Li b Ni p Mn q Co r O 2 wherein 1≦b≦1.5, 0.5≦p+q+r≦1, 0<p<1, 0<q<1, and 0<r<1, wherein, in the first lithium-containing transition metal oxide, the mole ratio (x/y) of Ni/Mn is 1.
2. The non-aqueous electrolyte secondary battery according to claim 1 , wherein the weight ratio of the mixture of the first lithium-containing transition metal oxide and the second lithium-containing transition metal oxide (the first lithium-containing transition metal oxide:the second lithium-containing transition metal oxide) is in the range of 2:8 to 8:2.