Methods of making and using electrode compositions and articles

An article comprising a cathode, wherein the cathode comprises:

• a first element selected from nickel or cobalt;
• a second element M selected from iron or cobalt, wherein said iron or cobalt is contained within a sulfide composition MxSy, wherein the ratio of x and y is between 0.5:1 and 1.2:1;
• at least one first alkali metal halide;
• and
• an electrolyte salt comprising a second alkali metal halide and a metal halide, wherein the electrolyte salt has a melting point in a range from about 150° C. to about 300° C.;
• wherein the molar ratio of the first element to the sulfur of the sulfide composition is between 1.5:1 and 50:1;
• wherein cobalt cannot be both the first element and the second element;
• and
• wherein the at least one first alkali metal halide and the second alkali metal halide may be the same or different.

An energy storage device comprising:

• (a) a first compartment comprising metallic alkali metal;
• (b) a second compartment comprising a cathode composition, said cathode composition comprising:
• (i) a first element selected from nickel or cobalt;
• (ii) a second element M selected from iron or cobalt, wherein said iron or cobalt is contained within a sulfide composition MxSy, wherein the ratio of x and y is between 0.5:1 and 1.5:1;
• (iii) at least one first alkali metal halide;
• and
• (iv) an electrolyte salt comprising a second alkali metal halide and a metal halide, wherein the electrolyte salt has a melting point in a range from about 150° C. to about 300° C.;
• wherein the molar ratio of the first element to the sulfur of the sulfide composition is between 1.5:1 and 50:1;
• wherein cobalt cannot be both the first element and the second element;
• and
• wherein the at least one first alkali metal halide and the second alkali metal halide may be the same or different;
• and
• (c) a solid separator capable of transporting alkali metal ions between said first and second compartments.