Preparation And Modification Of Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂

Li[Li0.2Mn0.54Ni0.13Co0.13]O2cathode materials were successfully synthesized via a simple sol-gel-combustion method, and the electrode process kinetics was studied. Carbon surface modified Li[Li0.2Mn0.54Ni0.13Co0.13]O2cathode materials were fabricated through a liquid phase route using polyvinylpyrrolidone (PVP) as carbon source. Meanwhile the effects of Li2MnO3and rGO surface modified LiMn1/3Ni1/3Co1/3O2were also studied.The results showed that the sample which synthesized at850℃for10h had the best electrochemical performance. At0.1C rate, the first discharge capacity was283.3mAh g-1, the capacity retention rate was80%after30cycles.Cyclic voltammetry (CV) analysis indicated that the lithium ion diffusion coefficient (Du+) of oxidation and reduction processes were9.79×10-12and3.58×10-12cm2s-1,respectively. Electrochemical impedance spectroscopy (EIS) results indicated that the Rct had minimum at4.0V, and the charge transfer resistance increased quickly with cycles. Du+calculated by EIS were1.91×10-11～9.17×10-13cm2s-1between3.8and4.2V. DLi+calculated by capacity intermittent titration technique (CITT) were3.45×10-14～1.02×10-15cm2s-1during the charge between2nd and10th cycle.The effects of carbon modification on the performance of the materials were investigated. The results showed that the structure of materials was not changed, but the electrochemical performances were improved by carbon modification. The initial discharge capacity of the carbon modified sample was293mAh g-1at0.1C, the capacity retention rate was81.3%after30cycles.The effects of LiMn1/3Ni1/3Co1/3O2surface modified by Li2MnO3and rGO were also studied. The results showed that the Li2MnO3+rGO hybrid surface modified sample had the best electrochemical performance. The first discharge capacity of LiMn1/3Ni1/3Co1/3O2hybrid surface modified by Li2MnO3+rGO was159.2mAh g-1at1C rate, the capacity retention rate was95.0%after40cycles.