Layered Of Lini <sub> 0.8 </ Sub> The Co <sub> 0.2 </ Sub> O <sub> 2 </ Sub> Doped Cathode Materials

LiCoO₂ has been widely used as a cathode material in commercial lithium ion battery layed .But due to the high cost and toxicity of Co , many efforts have been made to replace it. In practice, it is regularly argued that LiNi_0.8Co_0.2O₂ is a promising cathode materials to replace LiCoO₂, because it possess the merit of LiCoO₂ and LiNiO₂.The reaction conditions in co-precipitation process, pretreatment process and calcination process were analyzed and optimized. The precussor was prepared by control the pH value about 8,the ammonia concentration. Layered LiNo_0.8Co_0.2O₂ was synthesized with 5 % excess lithium under 750℃for 15h in atmosphere. The results of LiNo_0.8Co_0.2O₂ indicated that the LiNo_0.8Co_0.2O₂ delivered 179.2 mAh·g^-1at the rate of 0.1C during the voltage range of 2.7-4.3V.The capacity retention rateswas 93.2% after 10 cycles. The material shows an initial discharge capacity of 159.7 mAh·g^-1at the rate of 0.2C charge and 0.5C discharge during the voltage range of 2.7-4.3V. The capacity retention rates were 70.3% after 30 cycles.Doped LiNi_0.8Co_0.2O₂ were studied. The effect of Fe,Mg,Al on the performance of LiNi_0.8Co_0.2O₂ were explored. in Li (Ni_0.8Co_0.2) _0.95Al_0.05O₂,Li[(Ni_0.8Co_0.2)_0.95Al_0.05]_1-xFe_xO₂(x=0.02, 0.05, 0.1, 0.2),Li[(Ni_0.8Co_0.2)_0.95Al_0.05]_1-xMg_xO₂(x=0.02, 0.05). The performance of Li (Ni_0.8Co_0.2)_0.95Al_0.05O₂ was the best. The prepared Li (Ni_0.8Co_0.2) _0.95Al_0.05O₂ delivered the intial capacity of 155.7 mAh·g^-1 at 0.1C. The capacity retention rate was 98.3% after 10 cycles at the rate of 0.1C. it delivered the intial capacity of 142.8 mAh·g^-1 at the rate of 0.2C charge and 0.5C discharge during the voltage range of 2.7-4.3V. The capacity retention rate was 92.3% after 30 cycles.The doping of Fe and Mg deteriorates the performance of Li (Ni_0.8Co_0.2)_0.95Al_0.05O₂.