Mechanically alloyed composite anode materials based on SiO-Sn _xFe_yC_z for Li-ion batteries

A new family of composite materials as anodes for lithium-ion batteries, SiO-Sn_xFe_yC_z (x:y:z molar ratio), was synthesized by mechanical alloying. SiO is preferable because of its high capacity and the Sn-Fe-C alloys could be used as a buffer material to extend the cycle life of cells. Rather than expensive and toxic cobalt, we selected cheap and environmentally benign iron instead. The aim of this work is to find the optimal point by tuning the composition of Sn-Fe-C in the hope of obtaining better electrochemical performance. Different combinations were studied by high-energy X-ray diffraction and electrochemical methods. The results indicated that carbon can improve the cycle life, the amount of iron affects phase formation greatly, and the FeSn₂ phase should be avoided because of its detrimental effect on cycle life. The 50 wt% SiO-50 wt% Sn ₃₀Fe₃₀C₄₀ composition was studied using the pair distribution function and Mössbauer spectroscopy. This material exhibits high specific capacity (900 mA h g^-1 at C/6 rate) with good cycle life and rate capability. These results indicate that SiO-Sn _xFe_yC_z are promising candidate anode materials for commercial rechargeable lithium batteries. © The Royal Society of Chemistry 2013.