LI DIFFUSION IN A LIXW3O9F(X-GREATER-THAN-OR-EQUAL-TO-1) BASED ELECTRODE

The diffusion coefficient D of lithium in positive electrodes based on Li(x)W3O9F (x greater-than-or-equal-to 1) as starting material is determined by fitting the recovery of open-circuit voltage during relaxation periods following long-term discharges of Li/LiClO4-PC/Li(x)W3O9F type cells. A very sharp increase of D is observed between x = 1 and x approximately 1.15, followed by a very high and constant value for further intercalation. Furthermore, the presence of graphite in the electrode has little influence on D. These results are discussed on the basis of the crystal structure of the material, suggesting a very low mobility for the first lithium ion present (x = 1) and a very high one for those which are subsequently intercalated (x > 1).