Single-Crystal Intermetallic M−Sn (M = Fe, Cu, Co, Ni) Nanospheres as Negative Electrodes for Lithium-Ion Batteries

FeSn2, Cu6Sn5, CoSn3, and Ni3Sn4 single-crystalline nanospheres with a characteristic uniform particle size of ∼40 nm have been synthesized via a modified polyol process, aiming at determining and understanding their intrinsic cycling performance as negative electrode materials for lithium-ion batteries. We find that, in this morphologically controlled condition, the reversible capacities follow FeSn2 > Cu6Sn5 ≈ CoSn3 > Ni3Sn4, which is not directly decided by their theoretical capacities or lithium-driven volume changes. FeSn2 exhibits the best electrochemical activity among these intermetallic nanospheres and an effective solid electrolyte interface, which explains its superior cycling performance. The small particle dimension also improves cycling stability and Li+ diffusion.