Suppressing the Self‐Discharge of Supercapacitors by Modifying Separators with an Ionic Polyelectrolyte

Abstract The application of supercapacitors for energy storage is severely limited by their self‐discharging behavior. Herein, a convenient technique is reported to effectively suppress the self‐discharge of typical activated carbon‐based supercapacitors by modifying their porous cellulose separators with a cationic polyelectrolyte, polyethyleneimine. Experimental and theoretical studies indicate that polyelectrolyte modification slows the ion diffusion driven by concentration gradient, while does not sacrifice the electrochemical performances of the supercapacitors.