Electrodeposition of multivalent metal cations in nonaqueous solvents is ultimately
more difficult compared to aqueous systems. This is due to lower conductivity and a smaller
library of soluble electrolytes. In many cases, synthesis procedures are required to obtain
functional electrolytes. Comparison of these systems to aqueous counterparts is therefore very
challenging. In some cases, the solvent itself can be used as another platform for side reactions
to occur. Magnesium organohaloaluminate electrolytes in a THF solvent oxidize the solvent to
γ-butryolactone (GBL). This conversion slowly degrades the active electrolyte and causes films
of organic matter to build on the electrode surface as the magnesium metal is deposited and
redissolved over several cycles. A decrease in the reported coulombic efficiency (i.e. the
amount of charge removed from the surface to the amount deposited) is also observed for both
organohaloaluminates studied. In conjunction, the mass removed to the mass deposited is
always above 90% efficient. This suggests that uncharged mass is consistently deposited along
with magnesium in later cycles. Given this, the stability and lifetime of the
organohaloaluminates is lower than previously reported.
When electrodepositing other multivalent cations such as copper or zinc, information
regarding the general mechanism of the nucleation and growth can be gleaned by observing
chronoamperometric data at early times in a potential step experiment. When observed in an
aqueous environment, copper metal in a CuSO4 electrolyte deposits according to an
instantaneous model at pH 3 and a progressive model at pH 1. In a nonaqueous environment, a
similar system of CuCl2 shows instantaneous nucleation behavior. A direct comparison is not available due to the insolubility of CuSO4 in acetonitrile and copper deposition in water using CuCl2 is too quick to be observed
