A composition is provided that includes a ternary electrolyte having a melting point greater than about 150 degree Celsius. The ternary electrolyte includes an alkali metal halide, an aluminum halide and a zinc halide. The amount of the zinc halide present in the ternary electrolyte is greater than about 20 mole percent relative to an amount of the aluminum halide. An energy storage device including the composition is provided. A system and a method are also provided.