Nickel phosphorus trisulfide: an electroactive material for medium-temperature lithium batteries

In the present work the electrochemical behaviour of the layered NiPS3 compound with reference to lithium has been studied at 200°C in a cell which included an Li3Sn counter electrode and a molten LiSCN---KSCN eutectic mixture as the electrolyte. It has been found that electroreduction of nickel phosphorus trisulfide (NiPS3) proceeds in several stages at potentials from 2.7 to 1.8 V up to nearly a Li/Ni ratio of 7.5, then the products formed catalyse the electrolyte decomposition. It has been shown that the reversible behaviour of the NiPS3 electrode of a lithium battery is possible in carrying out charge/discharge cycles within the 0 ≤ Li/Ni ≤ 3 range, which considerably exceeds the region of the existence of the intercalation phase LixNiPS3 (0 ≤ x ≤ 1.5).