Se-doped Bi2S3 nanoneedles grown on the three-dimensional carbon foam as a self-supported anode for high-performance sodium ion batteries

Taking advantage of nano-sized active materials, doping and self-supporting, Se-doped Bi 2 S 3 /3D carbon foam (Bi 2 S 3-x Se x /CF) is synthesized through a pyrolysing-hydrothermal-heating three-steps process. The as-synthesized Bi 2 S 3-x Se x /CF hybrid exhibits a significant improvement in electrochemical performance, showing a high specific capacity of 441.8 mAh g −1 after 100 cycles with the coulombic efficiency approximating to 100%. The special nanoneedle-like structure of Bi 2 S 3 makes for shortening ion transmission distance, minishing the mechanical stress and thus improving the electrochemical performance. And the introduction of Se can enhance the specific capacity, cycling stability and rate performance by improving of electronic conductivity and forming Se-contained inactive phase during alloying process. Furthermore, the self-supporting electrode is beneficial to simplify preparation process and reduce the loss of volume energy density . The strategy presented in this paper to improve the electrochemical performance of secondary ions battery can be also applied to other novel electrodes materials.