Patent ID: 8748041

Claim:
A positive electrode active material for a lithium ion battery, said active material having a layered structure represented by the following compositional formula: Li x (Ni y M 1-y )O z in which M is one or more selected from the group consisting of Mn, Co, Mg, Al, Ti, Cr, Fe, Cu and Zr with the proviso that at least Mn is selected, x is within the range of 0.9-1.2, y is within the range of 0.5-0.95 and z is within the range of 1.8-2.4 wherein when A is defined as a value which is obtained by dividing an average of the peak intensities observed at 1420-1450 cm −1 and 1470-1500 cm −1 by the maximum peak intensity which appears at 520-620 cm −1 in an infrared absorption spectrum obtained by FT-IR, A satisfies the following relational formula: 0.24 y− 0.05≦ A≦ 0.48 y− 0.08.