MICROELECTRODE STUDIES OF THE LITHIUM PROPYLENE CARBONATE SYSTEM .1. ELECTRODE-REACTIONS AT POTENTIALS POSITIVE TO LITHIUM DEPOSITION

Voltammetry at nickel microdisc electrodes (radii 25 mum) in propylene carbonate has been used to investigated the chemistry which occurs at potentials positive to bulk lithium deposition and, hence, determine the surface for the commencement of lithium deposition. Presumably, similar reactions occur on the surface of lithium in contact with electrolyte. It is confirmed that a surface layer results from the reduction of oxygen and that water also reduces at a more negative potential; this reaction leads to another surface layer or a change in the composition of the layer resulting from oxygen reduction. It is also shown that the nickel substrate corrodes on open circuit in the presence of these surface layers. While other peaks are observed on the voltammograms, the evidence for assigning these to the reduction of solvent or electrolyte anion is weak.