The use of polarized light in the infrared reflectance spectroscopic investigation of the lithium-organic electrolyte interface

Surface films formed on lithium were investigated using in situ reflectance infrared spectroscopy. Experiments were carried out using sophisticated techniques like EMIRS (electro-modulated infrared reflectance spectroscopy) or SNIFTIRS (subtractively normalized interfacial Fourier-transform infrared spectroscopy). Spectra were recorded with both p- and s-polarized light to distinguish the surface species belonging to the passive layer from those in solution. The solutions used included LiAsF6 in mixtures of propylene carbonate, ethylene carbonate and dimethoxyethane (1:1:3). The main components detected at the surface films were lithium alkyl carbonates (ROCO2Li) and lithium carbonate (Li2CO3), this in agreement with previous work by Aurbach and co-workers. Besides, spectra reveal the presence of other types of species whose nature has been discussed.