Voltammograms and charge‐discharge curves are presented for carbon electrodes of varying graphitic crystallinity in
normalLiCl‐normalKCl
eutectic melt at 703°K (430°C). For rods of glassy carbon, graphite, and pyrolytic graphite there is a very marked cathodic depolarization below about −2.5V vs. a chlorine electrode. Chemical analysis of the cathodized carbons shows that this depolarization is caused by undervoltage deposition of alkali metal. The deposited metal normally consists entirely of Li but in two cases, during potentiostatic cathodizing, significant amounts of K were codeposited. Cathodized graphite rods disintegrate before reaching the Li potential but glassy carbon rods do not and can survive about 25 charge‐discharge cycles before breaking up. The uninflected charging curves obtained for glassy carbon and graphite give no indication of distinct transitions between Li intercalation compounds of different stages. However, the relatively low Li contents of cathodized carbons, their x‐ray diffraction patterns and the absence of acetylene in their reaction with water all favor the presence of intercalation compounds rather than a carbide. Lithium contents of glassy carbon rods cathodized toward the Li potential range up to about 7 weight per cent compared with 8.9% for
C6normalLi
, the richest intercalation compound and 37% for
Li2C2
. Even quite brief exposures of carbon electrodes in this melt to potentials below −2.5V have lasting effects on electrode behavior; carbon loses its melt‐repellency and the electrode suffers a 1–2V lowering of its open‐circuit voltage.