Oxygen Vacancy-Rich Nb2O5 as Cathode for Mg-Li Hybrid Ion Batteries

Due to the safe magnesium anode and fast Li + intercalation cathode, Mg-Li hybrid ion batteries (MLIBs) are considered to be one of the most promising candidates for electrical energy devices. However, developing cathode materials with good electrochemical properties is still a challenge for MLIBs. In this work, oxygen vacancy-rich Nb 2 O 5 cathode material was synthesized by a simple annealing treatment at high temperature. The results indicate that abundant oxygen vacancies are generated and a mass of original Nb 2 O 5 nanoparticles are formed on the surface of raw Nb 2 O 5 after annealing treatment. Density functional theory (DFT) analysis indicates that the oxygen vacancies could improve the conductivity of Nb 2 O 5 . The oxygen vacancy-rich Nb 2 O 5 delivers a high reversible capacity of 204.6 mA h g −1 at a current of 50 mA g −1 , and a cycling stability with capacity retention of 58.1% at 50 mA g −1 after 200 cycles, obviously higher than the oxygen vacancy-free Nb 2 O 5 with capacity retention of 23.3%. The improved reversible capacity and cycling stability are mainly attributed to oxygen vacancies, increased conductivity, and newly formed Nb 2 O 5 nanoparticles.