Porous carbon nanocages encapsulated with tin nanoparticles for high performance sodium-ion batteries

Sodium-ion batteries (SIBs) are recognized as an alternative to lithium ion batteries due to the abundance of sodium and potentially low cost of the whole battery system. One of the major challenges facing SIBs is to develop suitable anode materials with high capacity and long cycling life. Herein, we report the synthesis of porous carbon nanocage-Sn (PCNCs-Sn) nanocomposites as anodes of SIBs, demonstrating a high capacity of 828 mAh g−1 at 40 mA g−1. The electrodes also exhibited good rate capabilities (up to 3C) and superior cycling performances (1000 cycles). Post-mortem analyses verified the efficient volume change restriction by carbon nanocages and the well-preserved porous structure. Theoretical calculations indicated that the pulverization of bare Sn electrodes could be ascribed to strong bonds formed between amorphous carbon and the discharge product (Na15Sn4), which also deteriorated the conductivity. In contrast, the relatively weak interaction between Na15Sn4 and graphitic carbon can maintain superior conductivity and structural stability for better cycling performance.