[en] Highlights: • Stabilization of the SEI layer is a critical issue for improving the cyclability of SiNSs. • The FEC produces electrochemically and mechanically stable SEI layer. • The SiNSs with FEC showed the capacity of over 1500 mA h g⁻¹ with 95% efficiency after 200 cycles. Stabilization of the SEI layer that is formed by consuming active lithium in electrolytes is a critical issue for improving the cyclability of lithium ion batteries. We used SiNSs as anodes and investigated the effect of fluoroethylene carbonate (FEC) additives on the SEI layer. Our XPS, EIS and TEM analysis of CO and CO bonds, interfacial resistance and thickness of SEl layer, respectively, shows that the FEC produces electrochemically and mechanically stable SEI layer. The SiNSs with FEC showed the capacity of over 1500 mA h g⁻¹ with 95% efficiency after 200 cycles.