Abstract
The discharge characteristics of 
are much different from those of other layered materials. The discharge and charge characteristics strongly depend on the lithium diffusion in the van der Waals gap. In order to investigate the lithium diffusion, the cathode system was simplified by using the c‐axis oriented 
thin film prepared by chemical vapor deposition. The current‐time transient in the course of the potentiostatic discharge was calculated assuming the finite one‐dimensional diffusion of lithium. The diffusion coefficients were estimated from the comparison of the observed curve with the calculated one using the 
film. In the electrode potential region from 3.6 to 1.5 V vs. Li/Li+ of 
, the observed current‐time curve was in good agreement with the calculated one. The diffusion coefficient was estimated to be
. In the potential region from 1.5 to 1.2 V vs. Li/Li+, the simple diffusion model could not be applicable. The decrease in the crystallinity of 
occurred in this region. In the potential region from 1.2 to 0.9 V vs. Li/Li+, the observed curve was in agreement with the calculated curve. From these facts, it can be seen that the structural degradation occurs during the discharge and then the structural change is terminated when the electrode potential reached to 1.2 V. The diffusion coefficient was estimated to be 
which was larger than in the potential region from 3.6 to 1.5 V.