Ionic Exchange Mechanism in Electrical Double Layer Induced by Stable Passivation Film Boosts High Voltage Performance in Supercapacitors

Constructing a stable passivation film at the negative electrode–electrolyte interface is an effective strategy for optimizing the high voltage stability of propylene carbonate-based electrochemical double-layer capacitors (EDLC). However, the role of passivation film composition in determining high voltage performance is still being established. Herein, the effect of passivation film composition on the energy storage mechanism and high voltage performance is investigate. The modified passivation film inhibits the specific adsorption of anions; thus, the energy storage mechanism is altered to ionic exchange from co-ion desorption. This mechanism inhibits solvents from entering the inner Helmholtz plane, thus effectively reducing solvent decomposition and inhibiting rapid thickening of the passivation film. As expected, the floating stabilization time of EDLC utilizing this electrolyte at 3.3 V increases to 2090 h, which is 4.6 times longer than that for those utilizing commercial electrolyte. This work provides a new perspective for the development of high voltage EDLC.