Abstract: Thermal batteries using molten nitrate electrolytes offer significantly higher cell voltages and improvements in energy and power density. A problem concerning gas-evolution reactions is solved by eliminating chloride ions, sodium ions, and moisture contaminants. One step is to avoid any chlorine-containing substances in any battery component. The decomposition of such substances into chloride ions results in passivating-film breakdown and gas-producing reactions with the electrolyte. Sodium ions also react with the anode and lead to decreased stability. Thus, the use of sodium ions in components of the battery is avoided. The effect of water in the melt relates to both the reactivity and out-gassing problem. Water in the melt will react with, and breach the insoluble and protective oxide film and can produce hydrogen gas. A method to measure water in the nitrate electrolyte melt via cyclic voltammetry, as well as means of eliminate water from the melt is presented.

Abstract: Thermal batteries using molten nitrate electrolytes offer significantly higher cell voltages and improvements in energy and power density. A problem concerning gas-evolution reactions is solved by eliminating chloride ions, sodium ions, and moisture contaminants. One step is to avoid any chlorine-containing substances in any battery component. The decomposition of such substances into chloride ions results in passivating-film breakdown and gas-producing reactions with the electrolyte. Sodium ions also react with the anode and lead to decreased stability. Thus, the use of sodium ions in components of the battery is avoided. The effect of water in the melt relates to both the reactivity and out-gassing problem. Water in the melt will react with, and breach the insoluble and protective oxide film and can produce hydrogen gas. A method to measure water in the nitrate electrolyte melt via cyclic voltammetry, as well as means of eliminate water from the melt is presented.