Ionic Exchange\nMechanism in Electrical Double Layer\nInduced by Stable Passivation Film Boosts High Voltage Performance\nin Supercapacitors

Constructing a stable passivation film at the negative\nelectrode–electrolyte\ninterface is an effective strategy for optimizing the high voltage\nstability of propylene carbonate-based electrochemical double-layer\ncapacitors (EDLC). However, the role of passivation film composition\nin determining high voltage performance is still being established.\nHerein, the effect of passivation film composition on the energy storage\nmechanism and high voltage performance is investigate. The modified\npassivation film inhibits the specific adsorption of anions; thus,\nthe energy storage mechanism is altered to ionic exchange from co-ion\ndesorption. This mechanism inhibits solvents from entering the inner\nHelmholtz plane, thus effectively reducing solvent decomposition and\ninhibiting rapid thickening of the passivation film. As expected,\nthe floating stabilization time of EDLC utilizing this electrolyte\nat 3.3 V increases to 2090 h, which is 4.6 times longer than that\nfor those utilizing commercial electrolyte. This work provides a new\nperspective for the development of high voltage EDLC.