A variety of batteries employing metallic magnesium anodes are known. Morehouse et. al., in U.S. Pat. No. 2,759,986, taught a magnesium anode cup container lined with a cathode material paste consisting of powdered sulfur, graphite, and magnesium bromide electrolyte. Roche et. al. in Argonne National Lab, ERDA Report No. 76-35, "Alternative Secondary Cell Systems", Progress Report, 1976, pp. 53 to 54, discloses a molten electrolyte, magnesium-iron sulfide cell, using FeS.sub.2 cathodes, and MgCl.sub.2 -- NaCl -- KCl electrolyte. The cathode was covered with a stainless steel screen and the anode was covered with graphite fabric. The cell operated at 450.degree. C but short circuited after four cycles due to magnesium dendrite formation.
Others in the art have substituted iron sulfide as the cathode material in combination with a lithium anode. These lithium cells provide outstanding high voltage characteristics. Vissers et. al., in U.S. Pat. No. 3,933,521, taught a molten electrolyte, rechargeable, electrochemical cell which required a LiCl -- KCl electrolyte between the anode and cathode and operated at temperatures of about 400.degree. C. The cathode contains iron, cobalt or copper sulfides in a conductive support structure, insulated with a separate boron nitride or yttria cloth separator, and disposed in the center of a housing container. The anode which lines the bottom of the container comprises a 90% porous, compacted, stainless steel or nichel felt, coated with cobalt and impregnated with molten lithium.
The use of lithium, due to its high reactivity, requires the use of expensive separator and container materials. In lithium cells, the anode and electrolyte are very expensive. The use of magnesium metal provides severe short circuit complications due to dendritic growth at the magnesium electrode during recharging. Magnesium also reacts chemically with a wide variety of separator materials, particularly oxides, to make them electrically conducting, thus causing shorting of electrodes. What is needed, is an inexpensive, secondary, electrochemical cell, which will still provide good voltage characteristics, and which will not be easily degraded over long time periods.