A positive electrode composition is provided. The positive electrode composition includes at least one electroactive metal selected from the group consisting of titanium, vanadium, niobium, molybdenum, nickel, iron, cobalt, chromium, manganese, silver, antimony, cadmium, tin, lead, copper, zinc, and combination thereof, an alkali metal halide, and aluminum, present in an amount of at least 0.5 weight percent, based on the weight of the positive electrode composition. Optionally, an amount of sodium iodide of up to about 1.0 weight percent, based on the weight of the sodium halide in the positive electrode composition, is included. The composition may be included in a positive electrode with a molten electrolyte salt comprising the reaction product of an alkali metal halide and an aluminum halide. An energy storage device including the composition is provided, as well as a method of operating the device.