Ni2+-doped Na2Ti6O13 nanotubes to enhance the electrochemical performance of sodium ion batteries

Here, Ni2+-doped Na2Ti6O13 nanotubes (NNTONT) were successfully synthesized by a simple hydrothermal ultrasound method. It could be found that Na2Ti6O13 partly transformed to TiO2 with the addition of Ni2+, and affected the electrochemical properties of sodium ion batteries (SIBs). When the added Ni source got to 40 wt% (NNTONT-40), the capacity of charge–discharge approached the best value: 130.4 mAh/g after 100 cycles at 1C (1C = 177 mA g−1 in this paper), and increased by 41 % compared with undoped NTONT (92.2 mAh/g), and increased by 76 % even at a high rate (10C) after 1000 cycles. Subsequently, the analyses of CV (cyclic voltammetry), EIS (AC impedance spectrum) and GITT (galvanostatic intermittent titration technique) confirmed that Ni2+-doping resulted in lower Na+ insertion-extraction voltage, smaller charge transfer resistance and higher ion diffusion rate and lager BET specific surfaces. Therefore, Ni2+-doping is an effective strategy to improve the capacity, rate performance and energy density, which is a promising SIBs’ anode material.