MECHANISM OF REACTION IN NAALCL4 MOLTEN-SALT BATTERIES WITH NICKEL FELT CATHODES AND ALUMINUM ANODES .1. MODELING OF THE BATTERY PROPERTIESAT THERMODYNAMIC-EQUILIBRIUM

A theoretical description of the thermodynamic properties of the batte ry systems: Al/NaCl-AlCl3-Al(2)X(3)/Ni-felt (X = S, Se, Te) and the co rresponding system without chalcogen has been provided for cells with basic to slightly acidic NaCl-AlCl3 melts containing small amounts of chalcogen. The model developed describes the equilibrium concentration s of constituent species in the electrolyte and equilibrium potentials of the electrodes vs. number of coulombs passed through the cells. Fo r cells without chalcogen curves were calculated under the assumption of NiCl2 formation showing corresponding Variation of anode potential, cathode potential, and cell voltage as a function of electrolyte comp osition. For sulfide containing cells the plateau of lowest potential has been found to be associated with essentially pure nickel sulfide, NiySz. A procedure for model fitting to the cathode potential curve-fo rm of the NiySz-plateau is presented. A general equation is proposed f or the reaction taking place along the second plateau.