Electrochemical Behavior of Nonporous Ni/NiCl[sub 2] Electrodes in Chloroaluminate Melts

The electrochemical behavior of nonporous electrodes was studied using an cell in which the capacities of the cell were limited by the electrode. The limiting mechanism of the electrode was found to be associated with formation of on the surface of the nickel electrode. This phenomenon limits the mass‐transfer processes of the nonporous electrode and thus its area capacity density. Based on the results of these investigations, an electrochemical model of the electrode reactions was developed which predicts the performance characteristics of porous electrodes for various conditions of operation. Modifying the electrolyte with the NaBr, NaI, and sulfur additives was found to produce higher nickel utilization and lower impedance values due to doping effects, which is believed to open up the lattice for better mass transport. Solubility of the nickel chloride in sodium‐chloroaluminate melts as a function of temperature and additives was also determined. The solubility measurements indicated that the solubility of nickel chloride in the chloroaluminate melt is strongly dependent on the operational temperature of the cell and the chemical additives present in the electrolyte. The results of this study clearly indicate the importance of the chemical additives, basicity of the melt, and the lower operating temperature of the cell for improved performance and cycle life. © 2000 The Electrochemical Society. All rights reserved.