Thermodynamic and kinetic properties of lithium insertion into titanium misfit layer sulfides

Abstract

The thermodynamics and kinetics of the electrochemical intercalation of lithium into polycrystalline (PbS)_1.18(TiS₂)₂, (BiS)_1.14(TiS₂)₂, (PbS)_1.18TiS₂ and (SnS)_1.20TiS₂ have been studied by coulometric titration techniques. The highest values of the Gibbs energy of intercalation were obtained with (MS)_{1 +δ}(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 × 10^–10 cm² 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 +δ}(TiS₂)₂ stoichiometry, probably due to the presence of true van der Waals gaps created at the TiS₂/TiS₂ interface.