Effect of vanadium doping on the electrochemical performances of sodium titanate anode for sodium ion battery application.

In this study, V 5+ doped sodium titanate nanorods were successfully synthesized by a sol-gel method with different optimized vanadium concentrations. Before testing as a promising anode material for sodium ion battery (SIB) application, the samples were systematically characterized. It was clearly observed that V 5+ doping significantly affects the phase formation of sodium titanate samples and leads to the alteration of the major phase of Na 2 Ti 3 O 7 to a single Na 2 Ti 6 O 13 phase with increasing doping concentrations. Electrochemical investigations clearly showed that the optimized 15 wt% V 5+ doped sample exhibits the highest capacity of 136 mA h g -1 at 100 mA g -1 after 900 cycles as well as better rate capability than the undoped sample by delivering 101 mA h g -1 capacity at a high current density of 1000 mA g -1 . It is believed that the incorporation of highly charged V 5+ in sodium titanate produces oxygen vacancies along with partial reduction of Ti 4+ to Ti 3+ , resulting in improved electronic conductivity. The utilization of oxygen vacancies also preserves the integrity of the electrode, giving rise to long term cycling. Thereby, V 5+ doping was found to be an effective strategy to enhance the electrochemical performance of the sodium titanate anode for SIBs.