Electrochemical characteristics of LiNi1−xCoxO2 as positive electrode materials for lithium secondary batteries

Physical properties and electrochemical behavior of LiNi1−xCoxO2 (0.1≤x≤0.9) were investigated for use as positive electrode material in lithium secondary batteries with long cycle life. LiNi1−xCoxO2 are characterized by an α-NaFeO2 type structure. In a three-electrode test cell, LiNi0.7Co0.3O2 showed a large discharge capacity of 159 Ah kg−1, and good cycle performance, with a discharge capacity deterioration ratio of 0.73% per cycle. In a 2 Wh-class cell, LiNi0.7Co0.3O2 exhibited a discharge capacity of 520 mAh, and good cyclability, with a discharge capacity deterioration ratio of 0.026% per cycle. LiNi0.7Co0.3O2 is a promising positive electrode material, having the largest discharge capacity and the best cycle performance in the series of LiNi1−xCoxO2 compounds.