IRON AND NICKEL-PHOSPHORUS TRISULFIDES AS ELECTROACTIVE MATERIALS FORPRIMARY LITHIUM BATTERIES

The theoretical specific capacities of a family of layered compounds M PX(3) (M = Fe, Co, Ni; X = S, Se) for current-producing reactions invo lving 1.5, 2, 6 and 9 lithium atoms per MPX(3) molecule have been esti mated. These data show that FePS3 and NiPS3 are good electroactive mat erials for primary lithium cells. Conditions which allow one to shorte n substantially the synthesis time of iron and nickel phosphorus trisu lfides in ampoules are presented. According to conductivity measuremen ts in the 293-673 K temperature range, NiPS3 is an intrinsic and FePS3 an extrinsic semiconductor. The discharge characteristics of Li/MPS(3 ) (M = Fe, Ni) cells with an organic electrolyte have been studied; th ey confirmed that the participation of nine electrons in the redox pro cess is possible. For a primary button cell of the standard size 2325, with a FePS3 cathode, the specific capacity and specific energy value s obtained in a discharge 1.8-1.2 V range at load resistances of 3.0 t o 30 k Omega were 500-1160 Ah/kg and 700-1770 Wh/kg (on a pure FePS3 b asis), respectively.