Impedance Analysis for Oxygen Reduction in a Lithium Carbonate Melt

Oxygen reduction on a smooth gold electrode in a pure lithium carbonate melt was investigated by electrochemical impedance spectroscopy and cyclic voltammetry. The impedance data were analyzed using the Randles-Ershler equivalent circuit to determine parameters such as the charge-transfer resistance, Warburg coefficient, double-layer capacity, and uncompensated electrolyte resistance. The parameters estimated by complex plane plots and a complex nonlinear least squares method are in good agreement. Cyclic voltammetric measurements showed that oxygen reduction in a lithium carbonate melt is very rapid. A mass transfer parameter, DC0, estimated by the cyclic voltammetry concurred withthat calculated by the electrochemical impedance spectroscopy technique. The temperature dependences of the exchange current density and the product DC0 were examined, and the apparent activation energies were determined to be 121.7 ± 24.4 and 181.0 ± 7.0 kJ/mol, respectively