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

Abstract

In this study, V⁵⁺ 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 V⁵⁺ doping significantly affects the phase formation of sodium titanate samples and leads to the alteration of the major phase of Na₂Ti₃O₇ to a single Na₂Ti₆O₁₃ phase with increasing doping concentrations. Electrochemical investigations clearly showed that the optimized 15 wt% V⁵⁺ 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 V⁵⁺ in sodium titanate produces oxygen vacancies along with partial reduction of Ti⁴⁺ to Ti³⁺, resulting in improved electronic conductivity. The utilization of oxygen vacancies also preserves the integrity of the electrode, giving rise to long term cycling. Thereby, V⁵⁺ doping was found to be an effective strategy to enhance the electrochemical performance of the sodium titanate anode for SIBs.