## 3 Results and Discussion
### Electrochromic Switching Characteristics  
To investigate the switching processes of the films, their optical transmittance \(T_{\lambda}\) was measured _in operando_ during CV analysis. As expected, the reduction of WO\({}_{3}\) and the intercalation of Li\({}^{+}\) led to a decrease of \(T_{\lambda}\) (Figure 6b) and deeply blue-colored films as shown by the transmittance spectra at a potential of \(-1.0\) V (Figures 7 and S11) and the color impressions, which were calculated as reported in [60]. \begin{table}
\begin{tabular}{c c c} \hline
**Film Type** & \(\mathbf{K_{1}/\gamma}\) & \(\mathbf{K_{2}/\gamma}\) \\ \hline WO\({}_{3|}\)comp & 66–84 & 92–100 \\ WO\({}_{3|}\) up400 & 92–96 & 94–97 \\ WO\({}_{3|}\) up600 & 87–98 & 91–99 \\ WO\({}_{3|}\) mp & 69–77 & 95–96 \\ WO\({}_{3|}\) up & 93–96 & 95–97 \\ commWO\({}_{3}\) & 96 & 97 \\ \hline \end{tabular}
\end{table} 
Table 6: Reversibility of the electrochromic switching determined from the first (\(K_{1}\)) and second (\(K_{2}\)) cycle of the CV measurements at a scan rate of 5 mVs\({}^{-1}\) measured for at least 2 specimens of a given kind (commWO\({}_{3}\) only measured once). \begin{table}
\begin{tabular}{c c c} \hline
**Film Type** & \(\mathbf{D_{\rm a,CV}/cm^{2}\cdot s^{-1}}\) & \(\mathbf{D_{\rm c,CV}/cm^{2}\cdot s^{-1}}\) \\ \hline WO\({}_{3|}\)comp & 6.0 \(\times\) 10\({}^{-11}\) & 3.4 \(\times\) 10\({}^{-10}\) \\ WO\({}_{3|}\) up400 & 7.7 \(\times\) 10\({}^{-11}\) & 3.5 \(\times\) 10\({}^{-10}\) \\ WO\({}_{3|}\) up600 & 1.1 \(\times\) 10\({}^{-10}\) & 4.7 \(\times\) 10\({}^{-10}\) \\ WO\({}_{3|}\)mp & 6.0 \(\times\) 10\({}^{-11}\) & 2.5 \(\times\) 10\({}^{-10}\) \\ WO\({}_{3|}\)\(\mu\)mp & 6.2 \(\times\) 10\({}^{-10}\) & 1.1 \(\times\) 10\({}^{-9}\) \\ commWO\({}_{3}\) & 1.4 \(\times\) 10\({}^{-9}\) & 2.8 \(\times\) 10\({}^{-9}\) \\ \hline \end{tabular}
\end{table} 
Table 7: Effective diffusion coefficients \(D_{\rm a,CV}\) and \(D_{\rm c,CV}\) determined from CV. By reoxidation of WO\({}_{3}\) and deintercalation of the ions, \(T_{\lambda}\) reversibly increased [1; 6]. For the WO\({}_{3\,|}\)comp and the WO\({}_{3\,|}\)mp films (Figure S11b,c), \(T_{\lambda}\) in the bleached state was found lower compared to the initial state indicating partial irreversibility and the presence of trapped ions [39; 57] within the films. This is in accordance with their slightly lower reversibility \(K_{1}\) (Table 6). The WO\({}_{3\,|}\)mp400, WO\({}_{3\,|}\)mp600 and WO\({}_{3\,|}\)mp films (Figures 7 and S11a) could be fully bleached reaching transmittance characteristics close to the initial state. Facile deintercalation rather than trapping of ions as already revealed by the high reversibility (Table 6) is thereby confirmed. Comparing the change in transmittance at a wavelength of 710 nm upon reduction and reoxidation of the films (Table 8) reveals that for WO\({}_{3\,|}\)mp400, WO\({}_{3\,|}\)mp600 and WO\({}_{3\,|}\)mp films the transmittance modulation \(\Delta T_{\rm 710 nm}\) is larger than for the WO\({}_{3\,|}\)comp or WO\({}_{3\,|}\)mp films. These observations correlate well with the values of the effective diffusion coefficient (Table 7). Residual polymer fragments in the WO\({}_{3\,|}\)mp films might possibly hinder the diffusion of the ions within the mesoporous film structure leading to a change in transmittance comparable to compact films. Facile diffusion of ions supported by micropores present in the films prepared in the presence of PEG allows a high transmittance modulation, which has been also observed earlier for WO\({}_{3}\) prepared by dip-coating from similar precursor solutions [27]. The combination of PEG 600 with PIB\({}_{50}\)-\(b\)-PEO\({}_{45}\) led to films reaching even higher values for the transmittance modulation compared to the films prepared with PEG only (Table 8) indicating facilitated diffusion of ions through the film network composed of interconnected mesopores and pore clusters already revealed by SEM (Figure 1f).