CHEMICAL DIFFUSION-COEFFICIENT OF LITHIUM IN TITANIUM DISULFIDE SINGLE-CRYSTALS

The chemical diffusion coefficient of lithium and the activation energy for lithium diffusion in titanium disulfide were studied by the current pulse and the galvanostatic methods in the temperature range of 15 approximately 65-degrees-C, in particular regard to the influences of lithium concentration and excess titanium concentration (x and y in Li(y)Ti1+xS2). Titanium disulfide single crystals, with excess titanium concentrations of 0.03, 0.06, and 0.08, were synthesized by the chemical transport technique; some of these syntheses were followed by a sulfurization or a desulfurization reaction. The chemical diffusion coefficient was found to be a maximum when the lithium concentration is around 0.5. The maximum values in Ti1.03S2, Ti1.06S2, and Li1.08S2 are 1 x 10(-7) cm2/s, 5 x 10(-8) cm2/s, and 6 x 10(-9) cm2/s, respectively. The activation energy for lithium diffusion in Ti1.03S2 is 30 approximately 50 kJ/mol, and it decreases as the lithium concentration increases. The activation energy and its dependence on lithium concentration were not significantly influenced by the excess titanium concentration.