The optimum preparation condition and electrochemical properties of LiNiO 2 as the cathode material for lithium secondary batteries were investigated. LiNiO 2 samples were prepared from Li(OH) 2·H 2O and Ni(OH) 2 in the range from 500 to 900 °C. The compound prepared in an oxygen atmosphere at 700 °C exhibited the highest discharge capacity of 200 mAh/g in the voltage range from 3.0 to 4.3 V. The structure and charge-transfer resistance of the Li 1− x NiO 2 compound were examined at each state-of-charge by X-ray diffractometry and a.c. impedance spectroscopy. The charge-transfer resistances were low in the range of 0.15< x<0.75, which was related to the expansion of the interlayer distance between NiO 2 layers.