AN ELECTROCHEMICAL IMPEDANCE STUDY OF THE OXYGEN REDUCTION ON NONPOROUS NIO AND LICOO2 IN MOLTEN-CARBONATE

Non-porous electrodes of NiO and LiCoO2 are examined in molten carbona te half cells using electrochemical impedance spectroscopy. With this technique the charge-transfer resistance and diffusion properties of t he oxygen reduction were measured as a function of gas composition and compared to theoretical predictions. For both electrodes the super ox ide mechanism yields the best fit results, but the difference with the peroxycarbonate mechanism is very small. The exchange current densiti es of electrode processses are estimated from the R-ct and found to be approximately the same for both materials. By using potentiometry we showed that both electrode materials are not inert in molten carbonate . The stoichiometry of the samples depends on the Li content in the me lt due to Li-doping of NiO and the Li-insertion reaction in LiCoO2.