LiC(SO2CF3)3, a new salt for Li battery systems. A comparative study of Li and non-active metal electrodes in its ethereal solutions using in situ FTIR spectroscopy

The surface chemistry of lithium electrodes and non-active electrodes polarized to low potentials in LiC(SO2CF3)(3) solutions in 1-3-dioxolane (DN) and tetrahydrofuran (THF) was rigorously investigated using three different modes of in situ FTIR measurements. One method is based on external reflectance (SNIFTIRS type) and two methods are based on internal reflectance modes. In addition, Li electrodes treated in these solutions were also studied using ex situ FTIR external reflectance mode. For a comparison, the surface chemistry of these electrodes in LiAsF6 and LiN(SO2CF3)(2) solutions in the same solvents was also investigated using in situ and ex situ FTIR spectroscopy. It was found that while in LiAsF6 solutions the surface chemistry developed is dominated mostly by the solvent reduction, in the other two salt solutions, the salt anion reduction products are the major constituents in the surface films formed. The LiN(SO2CF3)(2) is more reactive towards Li than LiC(SO2CF3) ir. these systems. The differences in Li cycling efficiency and morphology observed in the three salt solutions are discussed in light of the difference in the surface chemistry developed on lithium.