Sb@C coaxial nanotubes as a superior long-life and high-rate anode for sodium ion batteries

Antimony (Sb) is an attractive anode material for sodium-ion batteries (SIBs) with a high theoretical capacity of 660 mAh g(-1). However, its practical application is greatly hindered by the rapid capacity fading which is largely due to the large volume expansion during sodiation. Tuning the morphology and structure at the nano-scale or using carbonaceous materials as the buffer layer is essential to address this issue. Here, a facile carbon-coating coupled with a thermal-reduction strategy has been developed to synthesize unique Sb@C coaxial nanotubes. With different annealing time, the hollow space and the amount of Sb inside the tube can be easily tuned by the partial evaporation of Sb. The as-obtained Sb@C nanotubes exhibit excellent sodium storage properties. The remarkable electrochemical performance results from the unique coaxial nanoarchitecture. Specifically, it delivers a high specific capacity of 407 mAh g(-1) at 100 mA g(-1) after 240 cycles. Furthermore, a stable capacity of 240 mAh g(-1) can be retained at 1.0 A g(-1) even after 2000 cycles. Most importantly, high capacities of 350 mAh g(-1) and 310 mAh g(-1) can be achieved at large current densities of 10 and 20 A g(-1), respectively, which represents the best rate performance among the reported Sb-based anode materials.