Synthesis and Characterization of New Intercalated Lithium Cathodes
Layered MPXn (n = 3 and 4) have a structure closely related to the CdI2 and CdCl2 types. In their Van der Waal’s gap, they present octahedral sites. These sites are larger in the sulfide derivatives than in the corresponding disulfides of transition elements. In the octahedral interstices, lithium intercalates (M being a transition metal) without parameter expansion. Such property can be used in a battery MPXn /electrolyte/Li, in which topochemical intercalation takes place electro-chemically. The synthesis and physical properties of the two dimensionnal phases have been completed, along with chemical and electrochemical lithium intercalation. A study on NiPS3 showed this material to be stoechiometric. Only the MPX- group exhibited promising behaviour, and particularly NiPS3, FePSe3 and FePS3. Open potential circuit and magnetic measurements, NMR of 7Li and 31P indicate that, in the case of Lix NiPS3 (O < x < 1.5), the intercalation takes place through two phases (Li0.5 Nips3 and Li1.5Nips3). High current density discharge curves carried out on the three above compounds have revealed some solvent interaction during intercalation. Such interaction improves the reversibility of the generator, at least in the case of NiPS3.
KeywordsNickel Sulfide Hydrated Chromium Lithium
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