Stable sodium-ion battery anode enabled by encapsulating Sb nanoparticles in spherical carbon shells

Antimony (Sb) has been recognized as one of the most promising metal anode materials for sodium-ion batteries, owing to its high capacity and suitable sodiation potential. Nevertheless, the large volume variation during (de)alloying can lead to material fracture and amorphization, which seriously affects their cycling stability. In this work, we report an engineering strategy by encapsulating Sb nanoparticles in nitrogen-doped spherical carbon shells (Sb@CN). This unique structure can efficiently accommodate volume variation and release stress upon sodiation, thus maintaining structural integrity. As a result, the Sb@CN composite exhibits an excellent sodium storage performance, achieving a capacity of 282 mAh g−1 over 5000 cycles at the current density of 0.66 A g−1, and the capacity retention rate from the second cycle to the 5000th cycle is close to 100%. Moreover, it also shows a remarkable rate capability of 217 mAh g−1 at a high current density of 3.3 A g−1. It is believed that this composition strategy would provide guidance toward stable alloy anodes for sodium-ion batteries.