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Building a Cycle-Stable Fe-Si alloy/Carbon Nanocomposite Anode for Li-Ion Batteries through a Covalent Bonding Method.

Si is being intensively developed as a safer and high performance anode for next generation Li-ion batteries, however, its battery application still remains challenging due to its low cycling Coulombic efficiency. To address this issue, we chose a conjugated polymer, polynaphthalene (PN), as carbon precursor and a low-cost commercial ferrosilicon (Fe-Si) alloy as active phase to prepare a Fe-Si/C nanocomposite with core-shell-like architecture through sand milling-assisted covalent bonding method, followed with a carbonization reaction, thus forming a covalently bonded carbon coating on the surfaces of Fe-Si alloy nanoparticles. Benefitting from the greatly reduced volumetric expansion of Fe-Si alloy cores in lithiation process and the stable interface provided by the outer carbon shell, the thus-prepared Fe-Si/C nanocomposite exhibits a high structural stability at repeated charge/discharge cycles. The experimental results reveal that the Fe-Si/C composite anode can demonstrate a high reversible capacity of 1316.2 mA h g-1 with an active mass utilization of 82.6 %, a long-term cycle stability more than 1000 cycles even at a considerably high current rate of 2.0 A g-1, and in particular, a high cycling Coulombic efficiency of 99.7%, showing a great prospect for application in practical LIBs.