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 safe and high-performance anode for next-generation Li-ion batteries (LIBs); however, its battery application still remains challenging because of its low cycling Coulombic efficiency. To address this issue, we chose a conjugated polymer, polynaphthalene, as a carbon precursor and a low-cost commercial ferrosilicon (Fe–Si) alloy as the active phase to prepare a Fe–Si/C nanocomposite with a core–shell-like architecture through sand milling-assisted covalent-bonding method, followed by 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 the lithiation process and the stable interface provided by the outer carbon shell, the thus-prepared Fe–Si/C nanocomposite exhibits a high structural stability in 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 of 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 great prospect for application in practical LIBs.