Transport and electrochemical properties of high potential tavorite LiVPO4F

Abstract Tavorite-structured 4 V-class LiVPO 4 F as a safe and durable cathode material for lithium-ion batteries (LIBs) has been studied. The electrical transport and ionic diffusion properties of LiVPO 4 F at different temperature and at different charge–discharge states have been systemically investigated for the first time. At room temperature, LiVPO 4 F shows a relatively high bulk ionic conductivity of ~ 8 × 10 − 7  S cm − 1 but a poor electronic conductivity of ~ 10 − 11  S cm − 1 . This work uncovers an abnormal non-Arrhenius temperature dependence of electrical conductivity in the temperature range of 30–90 °C for tavorite LiVPO 4 F. Li + diffusivity of Li 1 −  x VPO 4 F (0 ≤  x  ≤ 1) at different delithiated/lithiated states and have been comprehensively studied for the first time, through galvanostatic charge–discharge, galvanostatic intermittent titration technique (GITT), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The electronic insulating nature may be the main bottleneck towards high rate performances for LiVPO 4 F at room temperature. To tackle this challenge, the strategy of carbon coating has been adopted in this work. The LiVPO 4 F/C composite exhibits impressive rate capability and good long-term cyclability at both room temperature and elevated temperature (55 °C).