“…Among the various hybrid ECs using redox-active aqueous electrolytes, the iodide-based one is probably the most suitable owing to the redox potential being very close to the equilibrium potential of the cell [25], which drives the battery-like positive electrode to work at a constant potential, while the negative electrode stores charge mainly in the electric double-layer (EDL). So far, hybrid ECs using either potassium iodide (KI) [14,26,27], Li 2 SO 4 + KI [15], MnSO 4 + KI [22] or choline nitrate + choline iodide-based electrolytes [24] have been proposed, and in all these systems, the potential of the positive electrode is nearly constant, while the negative electrode works in a large potential range using more than 90% of the cell potential window. Although the advantageous confinement of polyiodides inside the carbon pores of positive electrode prevents its self-discharge [28], the shuttling of iodine to the negative electrode cannot be fully prevented which affects the cycle-life of the hybrid cell [29].…”