Crystal Structure and Electrochemical Performance of a New Lithium Trivalent Iron Silicate

A new lithium iron silicate cathode material with only trivalent iron was obtained by aging Li 2 FeSiO 4 /carbon composite for one year at room temperature. Crystal structure of the new material was supposed to belong to monoclinic system in space group P 2 1 /n with cation disordering of Li + and Fe 3+ based on the Rietveld refinement and transmission electron microscopy (TEM) observation. The new material evaluated using lithium foil as an anode showed initial charge and discharge capacities of 243 and 182 mAh g −1 and stable charge-discharge one of about 150 mAh g −1 at the second cycle. Only trivalent iron was observed for the new material after initial charge by 57 Fe Mössbauer spectroscopy, suggesting the contribution of other redox species except for Fe ion. The new material with trivalent iron is stable in air and can deliver stable charge-discharge capacity, promising to be potential cathode material for lithium-ion batteries.