Deposition and Dissolution of Lithium through Lithium Phosphorus Oxynitride Thin Film in Some Ionic Liquids

Electrochemical deposition and dissolution of lithium were investigated in some aprotic ionic liquids through a typical inorganic Li ion conductor, lithium phosphorus oxynitride (LiPON) thin film. In 1-butyl-1-methylpyrrolidinium (BMP+) and 1-ethyl-3-methylimidazolium (EMI+) bis(trifluoromethyl-sulfonyl) amide (TFSA(-)) 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 LiPON thin film acted as an artificial solid electrolyte interphase film, in which Li ion was transported between the ionic liquids and the LiPON thin film.