Effects of carbon on the structure and electrochemical performance of Li₂FeSiO₄ cathode materials for lithium-ion batteries

A Li₂FeSiO₄/C composite cathode material was prepared by a solid-state method with sucrose as a carbon source. The effect of carbon on the structure and electrochemical performance of Li₂FeSiO ₄/C cathode materials for lithium-ion batteries was investigated. The materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), galvanostatic charge-discharge tests and electrochemical impedance spectroscopy (EIS). SEM images show that the obtained Li₂FeSiO₄/C materials consist of partially agglomerated nanoparticles with an average particle size of 100 nm. TEM images confirm that the carbon layer formed on the surface of Li₂FeSiO₄/C particles enhances the electronic conductivity and inhibits the agglomeration of the active particles during the annealing process. The electrochemical measurement results reveal that the Li ₂FeSiO₄/C composite with 7.5 wt% carbon shows a good electrochemical performance with an initial discharge capacity of 141 mA h g^-1 at 0.1 C. After 50 cycles, the discharge capacity of the Li ₂FeSiO₄/C composite remains 94.2% of the initial capacity at a discharge rate of 0.5 C.