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 Nb2O5 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 Nb2O5 nanoparticles are formed on the surface of raw Nb2O5 after annealing treatment. Density functional theory (DFT) analysis indicates that the oxygen vacancies could improve the conductivity of Nb2O5. The oxygen vacancy-rich Nb2O5 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 Nb2O5 with capacity retention of 23.3%. The improved reversible capacity and cycling stability are mainly attributed to oxygen vacancies, increased conductivity, and newly formed Nb2O5 nanoparticles.