Shuttle Effect Quantification for Redox Ionic Liquid Electrolyte Correlated to the Coulombic Efficiency of Supercapacitors

Abstract The use of redox‐active electrolytes is a good opportunity to increase the energy density of supercapacitors, the main limitation of this technology. The addition of redox molecules allows the storage of charge in the electrode and the electrolyte. The key to keeping the increase of charge is to avoid the shuttle effect of the redox molecule. Indeed, once the molecule is oxidized or reduced, it diffuses across the cell to react at the surface of the opposite electrode and the stored charge is lost. Is this shuttle effect however damageable for the device? This study proposes to answer this question by quantifying the shuttle effect and correlating it to the decrease of Coulombic efficiency of supercapacitors.