Structural Analysis during Charge-Discharge Process of Li2FeSiO4Synthesized by Molten Carbonate Flux Method

A Li 2 FeSiO 4 cathode material for lithium-ion batteries was synthesized by a molten carbonate flux method at 500°C. The Li 2 FeSiO 4 showed reversible capacity of 160 mAh g −1 at the 0.07 C rate in the voltage range of 1.5 − 4.2 V. Crystal structural change during charge–discharge process for the Li 2 FeSiO 4 was investigated using high-resolution synchrotron X-ray diffraction in order to understand charge-discharge performance. It was found that crystal structure of the Li 2 FeSiO 4 transformed to a new structure of a charged phase and a discharged one during the first charge-discharge. Crystal structure of the charged phase and the discharged one was supposed to have a monoclinic system with space group P 2 1 /n based on models of cations disordering of Li + , Fe 2+ and Fe 3+ .