Abstract:A Li₂FeSiO₄/C composite cathode for lithium ion batteries was synthesized at 650 ℃ by solid-state reaction. The effects of carbon sources and carbon content on the properties of the Li₂FeSiO₄/C composites were investigated. The crystalline structure, morphology, carbon content and charge/discharge performance of Li₂FeSiO₄/C composites were determined by X-ray diffraction(XRD), scanning electron microscopy(SEM), carbon/sulfur analyzer and electrochemical measurements. As carbon content increases in the range of 5%−20%, the amount of Fe₃O₄ impurity phase decreases. The SEM micrographs show that the addition of the carbon is favorable for reducing the Li₂FeSiO₄ grain size. Using sucrose as carbon source, the Li₂FeSiO₄/C composite with 14.5% carbon synthesized at 650 ℃ shows good electrochemical performance with an initial discharge capacity of 144.8 mA∙h/g and a capacity retention ratio of 94.27% after 13 cycles.

Key words: lithium ion battery; cathode; Li₂FeSiO₄