NOVEL IN-SITU AND EX-SITU TECHNIQUES FOR THE STUDY OF LITHIUM ELECTROLYTE INTERFACES

Various aspects of the reactivity of lithium toward propylene carbonat e (PC) and poly(ethylene oxide) (PEG) have been examined using ex situ and in situ spectroscopic techniques, respectively. Temperature progr ammed desorption of perdeuterated PC (d(6)-PC) layers condensed at abo ut 150 K on a clean Li film supported on an Au foil yielded a broad ml e peak, at temperatures in the range from 220 to 520 K (and thus much lower than that found for Li2CO3), which was tentatively ascribed to t he thermal decomposition of a lithium alkyl carbonate. A spectroelectr ochemical cell/environment controlled chamber has been designed and co nstructed to examine Li/PEO(LiClO4) electrolyte interfaces formed by L i electrodeposition on to a thin Au layer sputtered on the surface of a Ge internal reflection element in situ using attenuated total reflec tion Fourier-transform infrared (ATR/FT-IR) spectroscopy. This assembl y enables variable temperature measurements to be performed under cond itions of utmost cleanliness. Preliminary results have indicated that in the case of PEO/LiClO4 this ATR/FT-IR technique has sufficient sens itivity to observe changes in the composition of the surface and near surface region, including reaction products and perchlorate anions, wh ich contribute to the transport of charge in the electrolyte phase.