Synthesis and Electrochemical properties of Li[(Ni0.5Mn0.5)1-xCox]O2 cathode materials prepared by ultrasonic spray pyrolysis

초록

The layered lithium metal oxides, LiMO2 (M=Co, Ni, Mn) and the LiMn2O4 are most widely studied 4 V class cathode materials for lithium secondary batteries with high energy density. The LiCoO2 has been commercialized but has still some problems, such as its high cost, moderate, and toxicity. The LiNiO2 and LiMnO2 have been extensively studied as possible alternatives to LiCoO2. However, LiNiO2 still has some severe problems, such as difficulty in the synthesis of stoichiometric LiNiO2, capacity decay due to the formation of NiO2 phases and thermal instability. LiMnO2 is not thermodynamically stable as the layered structure. Manganese layered oxide are transformed to spinel phase during cycling. Accordingly, these materials have some problems for practical applications. Recently, Ohzuku et al. reported that the concept of Li[Ni1/2Mn1/2]O2 and Li[Ni1/3Co1/3Mn1/3]O2 were prepared by co-precipitation of nickel, manganese double hydroxide and nickel, cobalt, manganese triple hydroxide. In this work, the layered Li[(Ni0.5Mn0.5)1-xCox]O2 powders have been synthesized by ultrasonic spray pyrolysis method. We investigate the effects of synthesis condition, such as polymeric agents, calcination temperature and metal doping. The synthesis powers are delivered a discharge capacity of 170 mAh/g in the voltage range of 2.8 - 4.4 V.