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The typical behaviors of the transient and steady-state voltages for a reference-cell
is presented in Fig. 11.10. As a function of square root of time, the transient voltage
change shows usually a linear trend. Using these parameters, the diffusion coefficient
for each change in stoichiometry is reported in Fig. 11.11. The electrochemical active
area defined by the product of BET surface area and the active material mass is valid
for a description of the 2D surface area (dashed line in Fig. 11.11). The impact of
the free-standing structures on the electrode surface needs to be included in a 3D
description, for which their contribution relates to the top and surrounding walls
of every single structure. Based on the laser parameters used for the 3D structure
Fig. 11.10 Measured variables in the GITT for the evaluation of diffusion coefficient: a transient
E τ and b equilibrium E s potentials [51]
Fig. 11.11 Diffusion coefficient of Li-ions obtained by GITT as a function of stoichiometry [51]