FeSn5@Graphene Anodes for Li-Ion and Na-Ion Batteries

Intermetallic FeSn₅ new phase has emerged as promising alternative material for application in lithium ion batteries (LIBs) due to its highest theoretical capacity of 929 mAh g⁻¹ for the reported M(electrochemically inactive)-Sn intermetallic anodes. However, the cycling life and rate capacity of FeSn₅ electrode materials still remains a great challenge. Herein, we report for the first time a facile strategy to synthesize such well-organized composite of nano-sized FeSn₅ anchored on conducting graphene sheets as an advanced anode material for Li-ion and Na-ion batteries. The in situ synthesized FeSn₅@graphene composite exhibits excellent cyclic stability and good rate capability which was ascribed to the structure of homogeneous distribution of FeSn₅ nanospheres on graphene sheets that can improve electrical conductivity and accommodate structural stress due to its good conductivity, high surface area and mechanical flexibility. Further, the higher capacities of FeSn₅@graphene composites in LIBs than that in SIBs is ascribed to the large Na-ion radius, resulting in slow Na-ion diffusion and large volume change upon sodium insertion/extraction reactions in SIBs. For comparison, bare graphene and FeSn₅ nanocrystals were also prepared and investigated in detail.