Investigation On Synthesis And Performance Of LiNi_0.6Co_0.2Mn_0.2O₂ For Lithium-ion Batteries

The high-nickel cathode material LiNi_0.6Co_0.2Mn_0.2O₂has great potential in the field of vehicles and energy storage because of its high specific capacity,low cost and environmental friendliness.However,poor cycle stability has become a major obstacle to the entry of the high nickel cathode material LiNi_0.6Co_0.2Mn_0.2O₂ into the application market.Therefore,in this experiment,the properties of materials are supposed to be improved by optimizing the preparation.Then,the conditions of co-precipitation,sintering and modified material LiNi_0.6Co_0.2Mn_0.2O₂were explored systematically.In this paper,spherical precursor Ni_0.6Co_0.2Mn_0.2（OH）₂ with homogeneous composition and high tap-density was successfully prepared by hydroxide co-precipitation method.The effects of pH value,ammonia concentration and other technological conditions on the morphology and particle size of precursor Ni_0.6Co_0.2Mn_0.2（OH）₂ were systematically studied.The prepared precursor was investigated by SEM,Size,Tap density and other analysis methods,and the optimized conditions of hydroxide co-precipitation method were finally determined.Secondly,LiNi_0.6Co_0.2Mn_0.2O₂ was prepared by solid-state sintering.First,the precursor prepared under the optimal technological conditions was taken as the research object.The precursor Ni_0.6Co_0.2Mn_0.2（OH）₂ was calcined for 12 h at T1,T2,T3 and T4respectively to explore the effects of sintering temperature on the morphology,structure and electrochemical properties.The results show that NCM622-2 has high capacity and excellent cyclic stability.The first discharge capacity is 176.5 mAh·g^-1 at 1C current density,the capacity retention rate is as high as 92.0%after 100 cycles.In addition,NCM622-2 has excellent rate performance.The initial discharge capacity of NCM622-2 is103.6 mAh·g^-1 at 10 C current density.What’s more,the initial discharge capacity is still201.6 mAh·g^-1 when the current density restores to 0.1C which shows NCM622-2 has excellent structural stability.Therefore,the optimum sintering temperature was T2.Finally,NCM622-Gx was obtained by a simple and efficient electrostatic adsorption method,and the different amount of GONR was investigated thoroughly.The results of SEM shows that GONR wraps LiNi_0.6Co_0.2Mn_0.2O₂ particles in a three-dimensional network structure,and the morphology and structure of the modified LiNi_0.6Co_0.2Mn_0.2O₂ hardly changed.When the amount of GONR is 5 wt%,the cycle performance was the best.At the current density of 1 C,the first discharge capacity of NCM622-G5 is 179.4 mAh·g^-1,and the capacity retention rate is as high as 93.6%after100 cycles.Therefore,the optimal amount of GONR is 5 wt%.