Electrochemical and interfacial behavior of a FeSi2.7 thin film electrode in an ionic liquid electrolyte

► The FeSi2.7 electrode in ionic liquid electrolyte delivered a capacity of 756 mAh g−1. ► The FeSi2.7 electrode exhibited stable cycling behavior in ionic liquid electrolyte. ► The formation of stable SEI on the FeSi2.7 electrode led to good capacity retention.