Synthesis and electrochemical characterization of mesoporous Li$_{\mathbf{2}}$FeSiO$_{\mathbf{4}}$/C composite cathode material for Li-ion batteries

Lithium iron silicate (Li$_{2}$FeSiO$_{4})$ has the potential as cathode for Li ion batteries due to its high theoretical capacity ($\sim$ 330 mAh/g) and improved safety. The application of Li$_{2}$FeSiO$_{4}$ as cathode material has been challenged by its poor electronic conductivity and slow lithium ion diffusion in the solid phase. In order to solve these problems, we have synthesized mesoporous Li$_{2}$FeSiO$_{4}$/C composites by sol-gel method using the tri-block copolymer (P123) as carbon source. The phase purity and morphology of the composite materials were characterized by x-ray diffraction, SEM and TEM. The XRD pattern confirmed the formation of $\sim$ 12 nm size Li$_{2}$FeSiO$_{4}$ crystallites in composites annealed at 600 $^{\circ}$C for 6 h under argon atmosphere. The electrochemical properties are measured using the composite material as positive electrode in a standard coin cell configuration with lithium as the active anode and the cells were tested using AC impedance spectroscopy, cyclic voltammetry, and galvanostatic charge/discharge cycling. The Li$_{2}$FeSiO$_{4}$/C composites showed a discharge capacity of $\sim$ 240 mAh/g at a rate of C/30 at room temperature. The effect of different annealing temperature and synthesis time on the electrochemical performance of Li$_{2}$FeSiO$_{4}$/C will be presented.