Synthesis And Modification Study Of Lithium-rich Manganese Based Cathode Material Li[Li_0.2Ni_0.2Mn₍0.6]O₂

Abstract:Because of the high specific capacity, low cost, environment-friend and other advantages, Lithium-rich manganese based Lithium-ion battery cathode material Li[Li0.2Ni0.2Mn0.6]O2has become a new research hotspot in the field of power battery cathode materials. But the lower first columbic efficiency, poor rate and cycle performance has blocked its development. In this paper, Li[Li0.2Ni0.2Mn0.6]O2was synthesized by co-precipitation combined with high-temperature process. Ti and Co was doped to improve the electrochemical performance, simultaneously; the modified mechanism has been studied.MnSO4·H2O, NiSO4·6H2O, NH3·H2O, Na2CO3were used as raw marerials to synthesize precursor Ni0.25Mn0.75CO3by carbonate co-precipitation method, then mixed with Li2CO3, via high temperature, Li[Li0.2Ni0.2Mn0.6]O2was obtained. The structure and morphologies were characterized by XRD and SEM. Studies show the particle size of well-distributed precursor Ni0.25Mn0.75CO3is about20μm, and have the same crystal structure with MnCO3, The material Li[Li0.2Ni0.2Mn0.6]O2obtained at800℃for10h exhibited fine particle sizes and good electrochemical performance, its discharge specific capacity reach as high as247.4mAh/g at first cycle, The specific capacity of the material delivers190mAh/g at1C, capacity retention rate is over90%after50cycles. Initial exploration indicates the discharge specific capacity increases with the charge cut-off voltage increases.Li[Li0.2Ni0.2Mn0.6-xTix]O2(x=0.01,0.02,0.05,0.10) is synthesized by solid state method, the study reveal that the sample of x=0.02has the best electrochemical performance, The optimum sample delivers a specific capacity of232mAh/g,220mAh/g and203mAh/g at0.2C,0.5C and1.0C, discharge specific capacity is over230mAh/g in35cycles at0.1C; When x=0.10, the first coulomb efficiency can reach96.4%, but electrochemical performance declined, Further research is needed.Li[Li0.2Ni0.2-0.5xMn0.6-0.5xCox]O2(x=0.01,0.02,0.05,0.10) is synthesized by liquid phase doping method, the study show that discharge specific capacity has been improved as a result of Co doping, x=0.05is the best, the highest discharge specific capacity is270.5mAh/g, the capacity more than250mAh/g is released after35cycles at0.1C, the discharge specific capacity is exceeded210mAh/g after35cycles at1.0C, to a certain extent, Co-doping has improved the rate performance of this material.