Wet-Chemical Synthesis And Properties Of Li₂MSiO₄（M=Fe,Mn） As Cathode Materials For Lithium-ion Battery

The silicate Li₂MSiO₄（M=Fe, Mn） materials have attracted much attention due to theirhigh specific capacity. However, because it is difficult to synthesize the pure active phase, andthey exhibit a poor electrochemical cycling performance, hindering their application. In thisstudy, we investigate the wet-chemical synthesis process, in order to control theirmicro-nanostructure and enhance their electrochemical properties.The Li₂FeSiO₄/C nanocomposite material is obtained by sol-gel method. It has a porousaggregates structure at a microscale consisting on Li₂FeSiO₄nanoparticles. The dischargecapacity is154.6mAh/g in the first cycle and150.1mAh/g after the140th cycles at0.1C,with capacity retention near to97.1%. In addition, it would results in poor cyclingperformances when pre-hydrolyzing TEOS in the synthesis process. However, this shortensthe synthesis periods. In addition, the first specific capacity and efficiency increased due tobetter particle morphology.Using P123as addictive, the carbon coated Li₂FeSiO₄/C nanocomposite powder withgood dispersion is obtained though hydrothermal treatment, followed by calination at650℃.This material shows a good rate cycle performance. According to the chelating mechanism ofEDTA with Mn²⁺, the well-crystallinity and purity of Li₂MnSiO₄/C nanocomposite materialsare prepared. The materials exhibit an uniform nanoparticle size （⁵0nm）. The first andsecond discharge specific capacities are223mAh/g and310mAh/g at30mA/g, respectively.The materials maintain a charge capacity of94mAh/g at60mA/g, and the specific capacityloss is only14%after the20th cycles.