Preparation And Doping Modification Of LiNi Mn _0.3 Co _{O 2}

Layered cathode materials LiNi0.5Mn0.3Co0.2O2, with synergwastic effect of Ni, Mn and Co, shows a good electrochemical performance. However, its cycle stability, high rate current stability and high voltage stability need to be improved. In this paper, LiNi0.5Mn0.3Co0.2O2was synthesized by mixing nickel cobalt manganese hydroxide precursor prepared by co-precipitation with Li2CO3, roasting at high temperature. The influence of synthes conditions on its performance was discussed by changing factors one by one and optimized the synthes process. Modifying researches on lithium ion battery cathode materials by doping MgO, TiO2, Al(NO3)3was studied, and the structure, morphology, electrochemical performance was tested and analyzed.In this paper, the roasting temperature, lithium ratio and holding time of the LiNi0.5Mn0.3Co0.2O2cathode material was discussed, and the optimum process parameters as follows:roasting temperature of920℃, lithium ratio of1.06, holding time of15hours. Materials were synthesized under these conditions and tested at25℃,1C rate current between2.75and4.2V, the results show that the first discharge capacity was159.2mAh/g, the discharge capacity after100times cycles was141.0mAh/g, the capacity retention rate was88.6%. The cycling retention capacity after235times cycles was more than80%, indicating the material has good cycling performance. The discharge capacity of1C,2C,3C,4C rate under2.75-4.4V were174.2mAh/g,164.1mAh/g,155.1mAh/g and140.2mAh/g, respectively.In the experiments, the cycle performance of Mg2+doped LiNi0.5Mn0.3Co0.2O2cathode material at room temperature has been greatly improved. The cycling performance of the cathode materials when doped3%MgO was the best. The first discharge capacity reached150.6mAh/g at1C when charged at2.75-4.2V. The discharge capacity after100and200times was140.6mAh/g,135.4mAh/g, and the capacity retention rate was93.4%,89.9%, respectively.The cycling stability of Ti doped LiNi0.5Mn0.3Co0.2O2cathode materials charged at1C rate between2.75and4.2V were greatly improved. The first discharge capacity of LiNi0.5Mn0.3Co0.2O2cathode materials doped3%TiO2reach to a maximum of149.5mAh/g, and the discharge capacity after200times was142.3mAh/g, and the capacity retention rate was95.2%. The capacity retention rate after420times cycle was more than80%.The cycling stability was greatly improved of Li[Ni0.5Mn0.3Co0.2]1-xAlxO2which synthesized by doping Al. The best electrochemical performance of Al doped cathode material was doped with2%Al(NO3)3when charged at1C rate current between2.75and4.2V, which the first discharge capacity was150.0mAh/g and the capacity was137.0mAh/g after200cycles, the capacity retention rate was91.3%, and the cycling retention capacity after400times cycles was more than80%.