Patent ID: 7939203

Claim:
A lithium ion secondary battery comprising: (a) an anode; (b) an electrolyte; and (c) a cathode, said cathode comprising a lithium transition metal oxide cathode active material of the general formula Li x ((Ni 1−a−b (Ni 1/2 Mn 1/2 ) a Co b ) 1−k A k ) 2−x O 2 , wherein 0.65≦a+b≦0.85, 0.1≦b≦0.4, A is a dopant, 0≦k<0.05, and 0.95≦x≦1.05, said lithium transition metal oxide being substantially free of soluble bases such that less than 10 ml of 0.1M HCl is necessary to titrate 200 ml of a solution containing substantially all of the soluble bases present in 10 g of said lithium transition metal oxide to a pH less than 5, said solution being prepared by repeated soaking and decanting of said lithium transition metal oxide.