Synthesis and properties of FeSn₂-C composites as anode materials for lithium-ion batteries

Objective: Tin has a theoretical specific capacity as high as 990 mAh·g^{- 1}, and is thus a potential anode material for high- energy- density lithium- ion batteries. However, it suffers from a huge volume change during lithiation/delithiation process, leading to poor cycle performance. In this paper, core/shell structured FeSn₂-C composites were successfully synthesized by a simple high-energy ball milling technique with Sn, Fe, and graphite powder as raw materials. The FeSn₂-C composite was evaluated as an anode material for lithium- ion batteries. The influence of milling time and final phase composition on the microstructure and electrochemical performance of FeSn₂-C composites was systematically investigated. The failure mechanism of the FeSn₂-C electrode was also analyzed. The results reveal that long milling time can promote the mechanical alloying process of the FeSn₂ phase and reduce the particle size of the FeSn₂-C composite, which are beneficial for the increase of the specific capacity and the improvement of the cycle performance of the FeSn₂-C electrode. A high FeSn₂ phase content leads to a high specific capacity of the FeSn₂-Ccomposites but poor cycling stability of the electrode. The optimized Sn₂₀Fe₁₀C₇₀ composite prepared by ball milling for 24 h (500 r ·min^{- 1}) shows the best electrochemical performance with a capacity about 540 mAh·g^{- 1} for 100 cycles. The synthesized Sn₂₀Fe₁₀C₇₀ composite is a promising anode material for highenergy-density lithium-ion batteries.