Fluoroethylene carbonate (FEC) is proposed as the co-solvent for magnesium silicide (Mg2Si) anode in Li-ion battery. Comparing with ethylene carbonate (EC)+dimethyl carbonate (DMC) solvent, FEC + DMC solvent leads to much better cycling stability, such as 400 mAh g(-1) after 100 cycles. The effect of FEC is investigated in terms of XPS, SEM and electrochemical analysis, and vinylene carbonate (VC) is also studied to better understand the function of FEC. The results show that FEC adding significantly alter the solid electrolyte interface (SEI) formed on Mg2Si, it helps to build a much denser, robust and LiF-rich SEI. (C) 2018 Elsevier B.V. All rights reserved.