A positive electrode composition is provided. The positive electrode composition includes at least one electroactive metal, such as titanium, vanadium, niobium, molybdenum, nickel, cobalt, chromium, manganese, silver, antimony, cadmium, tin, lead, and zinc. The electroactive metal is present in an amount in a range from about 10 volume percent to about 20 volume percent, based on the volume of the positive electrode composition. The composition further includes iron, present in an amount in a range from about 0.2 volume percent to about 3 volume percent, based on the volume of the positive electrode composition; at least one first alkali metal halide; and an electrolyte salt. The electrolyte salt can be based on a reaction product of a second alkali metal halide and an aluminum halide, and has a melting point of less than about 300 degrees Celsius. An article, an energy storage device, and an uninterruptable power supply device that includes the positive electrode composition are also described; as is a method of forming the energy storage device.