Enhanced Electrochemical Properties of Li₃ VO₄ with Controlled Oxygen Vacancies as Li-Ion Battery Anode

Li₃ VO₄ , as a promising intercalation-type anode material for lithium-ion batteries, features a desired discharge potential (ca. 0.5-1.0 V vs. Li/Li⁺ ) and a good theoretical storage capacity (590 mAh g^-1 with three Li⁺ inserted). However, the poor electrical conductivity of Li₃ VO₄ hinders its practical application. In the present work, various amounts of oxygen vacancies were introduced in Li₃ VO₄ through annealing in hydrogen to improve its conductivity. To elucidate the influence of oxygen vacancies on the electrochemical performances of Li₃ VO₄ , the surface energy of the resulting material was measured with an inverse gas chromatography method. It was found that Li₃ VO₄ annealed in pure hydrogen at 400 °C for 15 min exhibited a much higher surface energy (60.7 mJ m^-2 ) than pristine Li₃ VO₄ (50.6 mJ m^-2 ). The increased surface energy would lower the activation energy of phase transformation during the charge-discharge process, leading to improved electrochemical properties. As a result, the oxygen-deficient Li₃ VO₄ achieved a significantly improved specific capacity of 495 mAh g^-1 at 0.1 Ag^-1 (381 mAh g^-1 for pristine Li₃ VO₄ ) and retains 165 mAh g^-1 when the current density increases to 8 Ag^-1 .