This work presents the effects of O2 flow rate and S-doping on structural and electrochemical properties of LiNiO2. Layered LiNiO2 were prepared using a sol-gel method. It was found that oxygen plays an important role in the crystallization of layered LiNiO2. The deficiency of oxygen in the crystallization process induced the inclusions of impurities and cubic rock-salt structure in LiNiO2 powders. For LiNiO2 prepared at high O2 flow rates, the electrode delivered high initial discharge capacity with a relatively good retention rate. S-doped LiNiO2 not only stabilized the structural integrity of the electrode material, but also increased the electrode performance.