Synthesis And Electrochemical Performances Of Orthosilicate As Cathode Material For Lithium Ion Batteries

In this work, Li2MnSiO4/C, Li2Mn1-xMgxSiO4/C composite cathode materials for lithium-ion batteries were prepared. The different factors that affect the structure, morphology and electrochemical performances of the silicate materials were studied. In addition, the deterioration mechanisms for Li2MnSiO4/C material were also investigated.Li2MnSiO4/C composite material was synthesized by sol-gel method with the optimized conditions. The precursor of Li2MnSiO4 was mixed with a certain amount of sucrose and ballmilled for 3 h, followed by a calcination in Ar/H2 at 600℃for 12 h. The as-prepared material delievers an initial discharge capacity of 203 mAh g-1 at a rate of 0.05C. About 1.22 Li per FU (formula unit) is reversibly exchanged during the first cycle.69% of the initial discharge capacity was remained after 20 cycles. The initial discharge specific capacity achieved up to 191 and 142 mAh g-1 respectively at a rate of 0.1 C and 0.5C.The deterioration mechanisms for Li2MnSiO4/C material were also investigated by ex-XRD, ex-XPS and CV technologies. The deterioration of the silicate crystal caused by Jahn-Teller effect and oxygen loss during the electrochemical cycle have been found to be the main reasons that account for the poor capacity retention.Mg doping orthosilicate materials, Li2Mn1-xMgxSiO4/C, were synthesized. The conductivity of the material increases by Mg doping, which benefit the performance of the orthosilicate material. A high initial charge/discharge capacity of 323/229 mAh g-1 has been achieved for the Li2Mn0.9Mg0.1SiO4/C sample.