MODEL FOR LITHIUM INTERCALATION INTO TIS2

By assuming that the presence of a Li+ ion in the van der Waals gap between two conducting TiS2 layers induces electronic charges in the layers, a semi-atomistic model was developed to explain the expansion of the c-axis of LixTiS2 and the decrease of the open circuit voltage of a Li-LixTiS2 cell, E(x), with increasing Li+ concentration. The results suggest that (1) only the six S atoms adjacent to the Li+ ion are displaced by its intercalation, and (2) the almost linear decrease of E(x) with increasing x can be explained with a double-layer capacitance of about 260 μF/cm2 between the Li+ ion layer and the adjacent TiS2 layers. It is shown that the discreteness of the charge on the Li+ ions is important in determining the values of the double-layer capacitance. © 1990.