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

Abstract

A FeSi2.7 thin film is deposited on a copper substrate by RF magnetron sputtering of a Fe-Si alloy target. The electrochemical behavior of the FeSi2.7 electrode in ionic liquid electrolyte based on 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl) imide is investigated and compared with that of a FeSi2.7 electrode in conventional liquid electrolyte. The FeSi2.7 electrode in the ionic liquid electrolyte delivers an initial discharge capacity of 756 mAh g(-1) at room temperature, and its discharge capacity is maintained to be 92% of the initial discharge capacity after the 100th cycle. AC impedance and FTIR analysis reveal that the formation of a stable solid electrolyte interphase (SEI) layer on the FeSi2.7 electrode in the ionic liquid electrolyte leads to a good capacity retention. This study demonstrates that the FeSi2.7 electrode exhibits stable cycling behavior and good interfacial characteristics in the ionic liquid electrolyte without any solvents and additives.