An article of electrochemical energy conversion is provided that includes a separator. The separator has a first surface that defines at least a portion of a first chamber, and a second surface that defines a second chamber, and the first chamber is in ionic communication with the second chamber through the separator. The energy storage device further includes a plurality of cathodic materials. The plurality includes at least a first cathodic material and a second cathodic material. Both of the cathodic materials are in electrical communication with the separator and both are capable of forming a metal halide. A proviso is that if either of the first cathodic material or the second cathodic material is a transition metal, then the other cathodic material is not iron, arsenic, or tin.