Self-supported Se-doped Na2Ti3O7 arrays for high performance sodium ion batteries

Na2Ti3O7, a titanium-based compound for sodium ion batteries (SIBs), stands out among anode materials because of its ultralow voltage plateau which leads to advanced energy density. However, the poor electronic conductivity and mediocre sodium ion storage capability are the main bottlenecks for its large-scale development. In this regard, self-supported Se doped Na2Ti3O7 arrays are innovatively proposed and different Se doping amounts are designed. It is concluded that the appropriate Se doping (Na2Ti3O6Se) could significantly enlarge the interlayer spacing, narrow the bandgap and decrease Na+ diffusion barrier, leading to enhanced reaction kinetics, which is also validated by the theoretical calculations in this work. As expected, the 0 anode exhibits a reversible capacity of 207 mAh g−1 after 100 cycles at 0.2 A g−1 in the voltage range of 0.01–3 V. A capacity of 155 mAh g−1 can be achieved after 1000 cycles at 1 A g−1. The experimental findings combined with theoretical calculations state that the Se doping protocol is an effective mean to modify the electrode materials.