IMPEDANCE SPECTROSCOPY OF LITHIUM ELECTRODES .3. THE IMPORTANCE OF LI ELECTRODE SURFACE PREPARATION

The influence of surface preparation on the impedance spectroscopy of Li electrodes in propylene carbonate solutions was investigated. Three methods were compared: (a) electrode preparation in a glove-box atmosphere including several atmospheric gases (e.g. O2, CO2); (b) electrode cleaning by anodic stripping; (c) surface preparation by shearing in solution. The surface films initially formed on Li electrodes prepared in the gas phase were analysed by surface-sensitive Fourier transform IR spectroscopy (ex situ, external reflectance mode). The data obtained from the impedance measurements and the related calculations and modelling of the Li/solution interphase formed in the various experiments seem to indicate that the first two methods lead to the formation of a highly porous interphase. Hence, the third method is preferred for electrode surface preparation since the interphase thus formed is more compact and ordered, and therefore the data obtained should be more reproducible.