New Cathode-anode Couples Using Nonaqueous Electrolytes

📖 The Scoop

New anode-cathode couples using nonaqueous solvents were investigated for use as secondary batteries for power sources in orbiting satellites. Initial criteria of selection of the couples is based on the theoretical energy-to-weight ratio calculated from the free energy of reaction of anode and cathode, which will be greater than 200 wh/lb. Cells with active metal anodes as alkali metals and light-weight cathodes meet this criteria. Since the electrolyte solution must be compatible with alkali metals; water, alcohols, and acids are excluded from use and nonreactive nonaqueous liquids will be used for the solvent system. A survey of physical properties of liquids indicates that certain nonaqueous systems have a wide temperature range of liquid state, high dielectric constant, and moderate viscosity, but electrical conductivities of nonaqueous solutions are less than othes of aqueous systems. Reversibility of anode and cathode reactions in nonaqueous media was studied by measuring the current efficiency for metal deposition or dissolution as a function of current density. At densities of 20 ma/sq cm, Mg from a Mg ethyl bromide-ethyl ether solution, K from a POCl3-KI system, Al from an AlCl2-n hexylamine-ethyl ether system showed low reversibility. High current efficiences were found for Li electrodeposition from a propylene carbonate Li salt system and for an AlCl3-ethyl pyridinium bromide-toluene system at 20 ma/sq cm current density. After anodic oxidation of many metals, NiCl2 and AgCl were insoluble in the propylene carbonate system; NiCl2 was insoluble in the AlCl3-ethyl pyridinium bromide-toluene solution.

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