Improved battery performance of Fe-doped LiVPO₄F with high capacity and stable cycling

LiVPO₄F is considered as an upgrade of current LiFePO₄ cathode for rechargeable lithium batteries due to its superior thermal stability and mildly high voltage plateau. However, the low intrinsic electric conductivity and sluggish electrochemical kinetics constrain its battery performance and practical development. Partial substitution of vanadium with iron is designed in this paper given the similarity of LiVPO₄F and LiFePO₄OH. The phase structure, particle size, battery performance and electrochemical kinetics of LiV_1-xFe_xPO₄F (0 ≤ x < 1) are comparatively studied. LiV_0.9Fe_0.1PO₄F is found having the optimal electrochemical performance, and delivers a reversible specific capacity of 132 mA h g⁻¹ and 80 mA h g⁻¹ at C/8 and 6C, respectively. After 300 cycles at 0.5C rate, the capacity slowly reduces from 119 mA h g⁻¹ to 108 mA h g⁻¹ with a retention of 90.8%.