Preparation And Electrochemical Properties Of LiNi_0.8Co_0.2O₂ By Microwave Co-Precipitation Method

A novel microwave co-precipitation method was used to synthesize LiNi_0.8Co_0.2O₂ cathode materials for lithium ion batteries. The LiNi_0.8Co_0.2O₂ powders were obtained by sintering the mixture of LiOH·H2O and Ni_0.8Co_0.2(OH)₂ precursor prepared by urea precipitation in nickel nitrate and cobalt nitrate solution. The Co²⁺ and Ni²⁺ co-precipitation in aqueous solution using urea as precipitator was carried out by microwave heating to allow the decomposition of urea. The prepared Ni_0.8Co_0.2(OH)₂ has the similar structure withα-Ni(OH)2 which is known as hydrated nickel hydroxide with an big interlayer separation(7.231?). The XRD patterns of the final LiNi_0.8Co_0.2O₂ product could be indexed by a hexagonalα–NaFeO2 structure (space group: 166, R 3? m) and no obvious impurity phase peaks could be observed, indicating that the synthesized samples were single phase.The sample LiNi_0.8Co_0.2O₂ has excellent electrochemical properties, which has an initial discharge capacity of 187.8 mAh/g with charging/discharging current of 16mA/g and voltage window of 3.0-4.3V at 25℃. After 40 cycles, the discharge capacity remains 161.8mAh/g, showing good cycling stability. However the rate performance of the prepared LiNi_0.8Co_0.2O₂ samples was not satisfying. It is necessary to dope the material to improve the high rate performance.In order to improve the high rate performance, aluminum and manganese were chosen to dope LiNi_0.8Co_0.2O₂ cathode material. The...