Titanium disulphide: A solid solution electrode for sodium and lithium

Single crystals of TixS2 (x = 0.002, 0.01, 0.02) have been incorporated into an electrochemical cell with propylene carbonate as an aprotic solvent. Sodium or lithium was electro-intercalated into the Van der Waals layers associated with these crystals using coulometric titrations to produce a solid solution electrode of the type MyTixS2, and open circuit voltages were measured as a function of the alkali metal content (0 < y < 1.0) at ambient temperatures. Discontinuities were observed in the emf-composition curves for sodium, but a smooth curve with a voltage span of only 0.5V (2.4 − 1.9V) was recorded for the intercalation of lithium. Electrochemical pulse experiments also enabled values to be derived for the chemical diffusion coefficients of sodium and lithium in MyTixS2. These values, which ranged from 10−6 to 10−10 cm2/s, were strongly influenced by the presence of extra titanium in the Van der Waals layer associated with increasing deviation from stoichiometry in the original TixS2 crystals.