Cyclic voltammetric investigation of the formation of intermetallic phases at a LiAl electrode in methyl acetate

Abstract

The formation of various Li/Al intermetallic phases at the LiAl electrode in methyl acetate was studied using cyclic voltammetry. The thickness of the α phase formed initially was estimated using the deposition and stripping method to be 1.1 nm. Repetitive cycling at the α or β phase potential led to a drastic increase in current over the first ten cycles before reaching a steady state. The formation of the β phase depended critically on the deposition potential and its presence at the electrode surface led to enhanced current in the reverse sweep, increased acceptance of deposited lithium, roughening and development of the area of the electrode upon cycling. The above effects were attributed to the difference in the lattice structure of the β phase as compared to the α phase, which greatly affected the electrode kinetics upon phase transition. The deposition of the more reactive LiAl alloys at more cathodic potential, namely −3.80 V, led to the formation of a passivating film which was broken down at more cathodic potential when the electrode surface had undergone vigorous chemical reaction with the solvent. Methyl acetoacetate was identified using i.r., n.m.r., u.v. and electrochemical techniques to be the major reaction product and a possible reaction mechanism was proposed.