Tin selenide/N-doped carbon composite as a conversion and alloying type anode for sodium-ion batteries

Sodium-ion batteries (SIBs) have attracted remarkable attention since they are considered a low-cost alternative for lithium-ion batteries (LIBs) for large scale energy storage system applications. Tin selenides such as SnSe and SnSe2 are earth-abundant, environmentally friendly, chemically stable, and capable candidates as the negative electrode for SIBs, in which the capacity is provided by a conversion reaction together with the alloying mechanism. However, these materials suffer from low conductivity, drastic volume changes, and aggregation of particles during the electrochemical reaction, which lead to poor cycling performance, hindering their practical application. The combination of tin selenide with conductive carbon is an effective strategy to overcome the issues mentioned above. Herein, we report tin selenide/N-doped carbon composite as an anode material for SIBs fabricated by solvothermal synthesis followed by a dry solid state method and calcination. The as-prepared tin selenide/N-doped carbon composite electrode delivers an initial discharge capacity of 460 mAh g−1 and maintained a discharge capacity of 348 mAh g−1 at the end of the 100th cycle at a current density of 200 mA g−1, which is almost 3.5 times higher in discharge capacity than the pristine electrodes. Moreover, the composite electrode exhibits outstanding rate capability compared to pristine tin selenide with a discharge capacity of 234 mAh g−1 even at a high current density of 1600 mA g−1. N-doped carbon provides improved conductivity as well as buffering the volume change during sodiation/desodiation, resulting in an overall enhancement of electrochemical performance.