Electrochemical characteristics of layered LiNi_1/3Co_1/3Mn_1/3O₂ and with different synthesis conditions

LiNi_1/3Mn_1/3Co_1/3O₂ had been successfully prepared from spherical composite carbonate via a simple uniform-phase precipitation method [P. He, H. Wang, L. Qi, T. Osaka, J. Power Sources, in press] at normal pressure, using nickel, cobalt and manganese sulfate and ammonia bicarbonate as reactants. The preparation of spherical composite carbonate was significantly dependant on synthetic condition, such as the reaction temperature, feed rate, molar ratio of these reactants, etc. The optimized condition resulted in spherical composite carbonate of which the particle size distribution was uniform, as observed by scanning electronic microscopy (SEM). Calcination of the uniform composite carbonate with lithium carbonate at high temperature led to a well-ordered layer structured LiNi_1/3Mn_1/3Co_1/3O₂ as confirmed by X-ray diffraction (XRD), without obvious change in shape. Due to the homogeneity of the composite carbonate, the final product, LiNi_1/3Mn_1/3Co_1/3O₂, was also significantly uniform, i.e., the average particle size was of about 10 μm in diameter and the distribution was relatively narrow. As a result, the corresponding tap density was also high, approximately 2.32 g cm^-3, of which the value is very near to that of commercialized LiCoO₂. In the voltage range of 2.8-4.2, 2.8-4.35 and 2.8-4.5 V, the discharge capacities of LiNi_1/3Mn_1/3Co_1/3O₂ electrode were 159, 168 and 179 mAh g^-1, respectively, with good cyclability.