Electrochemical deposition and dissolution of lithium were investigated in 1-butyl-1-methylpyrrolidinium (BMP+) and 1-ethyl-3-methylimidazolium (EMI+) bis(trifluoromethylsulfonyl)amide (TFSA(-)) ionic liquids containing LiTFSA through a typical inorganic lithium ion conductor, lithium phosphorus oxynitride (LiPON) thin film. In both BMPTFSA and EMITFSA containing 1 M LiTFSA, no cathodic current attributable to reductive decomposition of the ionic liquids was observed on the Ni electrode coated with the LiPON thin film. Electrochemical deposition and dissolution of Li were confirmed to occur through the LiPON thin film in both ionic liquids. Therefore, the UPON thin film acted as an artificial solid electrolyte interphase film, in which Li ion was transported from the ionic liquids to the interface between the Ni electrode and the UPON thin film. (C) The Author(s) 2015. Published by ECS. All rights reserved.