The thermodynamic and kinetic properties of silver intercalated niobium disulfide

A study of structures, thermodynamic and kinetic properties of Ag intercalated 2H-NbS₂ is reported. The observed phases Ag_xNbS₂, being a dilute gasphase (x<0.22) and a second- and first-stage phase (0.22≦×≦0.30 and 0.55 ≦×≦0.76 respectively) are structurally related. Silver atoms reside in tetrahedral holes between neighbouring sandwiches of NbS₂. Kinetic parameters of the mobile species (Ag) were obtained from ac response and the Galvanostatic Intermittent current Titration Technique (GITT), using samples of Ag_xNbS₂ as solid solution electrode in an AgI electrochemical cell above 425 K. Both first- and second-stage Ag_xNbS₂ exhibit fast ionic conduction. The relatively low chemical diffusion coefficient at 450 K, D̃ ≈ 10^-6.5 cm²s^-1, in the second-stage phase, as compared to that in the first-stage, D̃≈ 10^-4.5 cm²s^-1, is attributed to the coupling of the diffusion kinetics with stage conversion in islands type domains.