The in situ SAXS intensities (Fig. ) were fitted to three fit parameters: the I2 pore occupancy F P , the correlation parameter M Q of the iodine phase GRF ( ( )), and the parameter , accounting for ( ) (iodine) and ( ) (carbon) correlations. The I2 pore occupancy values were constrained to values smaller than 0.35, estimated from electrochemical capacity values (Fig. ). The value O Q was kept constant at a value of 30 nm (O Q ≈ ∞). To fit the in situ SAXS intensities, we minimized the sum of the squared residuum of all experimental SAXS intensities during a positive potential sweep. In other words, the parameters M Q and were held constant while the iodine pore occupancy was used as fit parameter for each SAXS curve at its specific state of charge. The procedure was repeated for several values of M Q and (Supplementary Fig. ) and the parameter set with the minimum sum of squared residuum values taken as the solution.