The Role of NiPS3 as a Cathode in Secondary Lithium Solid State Batteries

The transition metal phosphorus trisulfides have received considerable attention in recent years as a cathode element for the solid state secondary batteries. Detailed investigations into the structure1–3 physical properties4,5 of intercalates and electrochemical intercalation studies6–9 have contributed to the fundamental understanding of the chemical physics of Li-NiPS3 system. It has been shown7 that NiPS3, a material of structure similar to that TiS2, has on intercalation with Li a higher energy density. Three Li ions per molecular unit can be intercalated, two of them reversibly while keeping the electrode potential of the secondary cell at considerable value and the process of Li intercalation is completely reversible without causing any lattice expansion of the unit cell. Evidence of some intercalated phases was seen as a function of lithium composition also10