Research On Synthesis And Modification Of Li-rich Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ As Lithium-ion Battery Cathode Material

Solid solution lithium-rich material Li2MnO3-LiMO2 (M=Ni, Co, Mn, Cr…etc) has been extensively investigated as one of the most promising cathode materials for lithium ion batteries, due to its high specific capacity and good cycle capability. In this study, we have investigated the preparation methods and Na-doping affect on the structure and the electrochemical performance of Li1.2Mno.54Ni0.13Co0.13O2.The precursor was synthesized by co-precipitation method. The raw materials were MnSO4·H2O, NiSO4·6H2O, CoSO4·7H2O and Na2CO3 as precipitant agent. The pH value and temperature of the solution were precisely controlled at 8 and 40℃, respectively. The dry carbonate precursor was then thoroughly mixed with stoichiometric LiOH and Na2CO3.The mixed powders were pre-heated at 480℃ for 10 h and sintered at 900℃ for 12 h.The synthesized materials were characterized by XRD. The electrochemical measurements were carried out using Landz tester. The synthesized material delivers initial discharge capacity of 254 mAh g-1 with 100% capacity retention after 35 cycles. At high current density of 200 mA g-1, the discharge capacity was 150 mAh g-1, and can reach 134.5 mAh g-1 after 60 cycles.In addition, LiyNaxMn0.54Ni0.13Co0.13O2 (x+y= 1.2, r= y/x) cathode materials were successfully synthesized. Sodium doping could decrease the impedance value of the electrode. The Na+-doped sample with r=9 showed the best electrochemical performance, and the highest discharge capacity is 233 mAh g-1 at current density of 20 mA g-1. At current density of 200 mA g-1, the material showed high capacity retention of 90.7% after 60 cycles of charge/discharge.