In situ Raman and SAXS/WAXS were done in two-electrode hybrid supercapacitor cells comprising activated carbon (AC) electrodes and aqueous 1 M NaI electrolyte. The iodide/iodine redox reaction takes place at the positive electrode, while the negative electrode stores charge exclusively via electrical double-layer capacitance. Faradaic capacity (current) at the positive electrode would be limited by the capacitance (current) of an equally sized negative electrode . We increased the amount of iodine within the positive electrode by oversizing the negative AC electrode about 10-times in mass to exploit the Faradaic capacity and enhance the in situ Raman and SAXS/WAXS signals. The microporous AC has a mean pore size of 0.81 nm, a specific surface area of 1947 m 2 g -1 , and a specific pore volume of 0.84 cm 3 g -1 (Supplementary Table and Supplementary Fig. ). The experimental set-ups and cell assemblies are discussed in the Methods and sketched in Supplementary Fig. .