THERMODYNAMIC AND KINETIC-PROPERTIES OF LITHIUM INSERTION INTO TITANIUM MISFIT LAYER SULFIDES

The thermodynamics and kinetics of the electrochemical intercalation of lithium into polycrystalline (PbS)(1.18)(TiS2)(2), (BiS)(1.14)(TiS2)(2), (PbS)(1.18)TiS2 and (SnS)(1.20)TiS2 have been studied by coulometric titration techniques. The highest values of the Gibbs energy of intercalation were obtained with (MS)(1+delta)(TiS2)(2) stoichiometries, particularly in (PbS)(1.18)(TiS2)(2). The chemical diffusion coefficients of lithium for all compounds hardly varied with the amount of intercalated lithium and the maximum value, 6.5 x 10(-10) cm(2) s(-1), was found in (PbS)(1.18)(TiS2)(2). Micropolarization tests also showed that fast kinetics and better reversibility occurred in sulfides with (MS)(1+delta)(TiS2)(2) stoichiometry, probably due to the presence of true van der Waals gaps created at the TiS2/TiS2 interface.