Structural and Electrochemical Studies on Tavorite Crystal LiFePO4F Synthesized by Sol-Gel Process

Abstract

 LiFePO₄F as a cathode material for Li-ion (Li⁺) batteries is prepared by a novel sol-gel process followed by calcinations. The obtained crystalline powder is isostructural with amblygonite and tavorite, adopting a triclinic  space group that can apply a three-dimensional (3D) channel system for Li⁺ insertion/extraction. The particle size of the obtained material is 300-500 nm. The diffusion coefficient of the as-prepared sample, studied by electrochemical impedance spectroscopy (EIS), is higher than that of raw LiFePO₄ by three orders of magnitude, which confirms the fast Li⁺ migration in this material. The galvanostatic discharge-charge capacity is 145 mAh g^-1, which is close to the theoretical capacity of 152 mAh g^-1. Furthermore, the cyclic performance is excellent as well.