Patent ID: 7655357

Claim:
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 comprises 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 a Ni x Mn y O 2 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; or a mixture of the first lithium-containing transition metal oxide and a lithium cobalt oxide, wherein, in the first lithium-containing transition metal oxide, the mole ratio (x/y) of Ni/Mn is less than 1, and x+y<1.