In situ FTIR Spectroelectrochemical Studies of Surface Films Formed on Li and Nonactive Electrodes at Low Potentials in Li Salt Solutions Containing CO₂

Surface films formed on Li and noble metal electrodes at low potentials in salt solutions saturated with CO₂ were investigated using in situ Fourier transform infrared spectroscopy (FURS). Two methods have been used: subtractively normalized interfacial FTIRS (SNIFTIRS)-type measurements, external reflectance mode (thin layer cell configuration) and internal reflectance mode. The solutions used included LiAsF_e in propylene carbonate, tetrahydrofurane, and methylformate. It was found that Li₂CO₃ is a major surface species formed, and its precipitation suppresses solvent-related surface reactions on the active electrode surfaces. A coproduct of Li carbonate seems to be CO gas.