Suppressing hydrogen evolution with artificial interfaces for high-voltage and wide-temperature aqueous supercapacitors

초록

Extending the voltage window of aqueous electrolytes is essential for advancing high-energy supercapacitors. Water-in-salt electrolytes (WiSEs) broaden the electrochemical stability window (ESW), but at the expense of rate performance and subzero-temperature operability. In contrast, dilute electrolytes preserve fast ion kinetics and temperature tolerance, but their limited ESW prevents high-voltage operation. Here, we introduce an artificial interfacial engineering strategy that decouples interfacial stability from bulk electrolyte properties, thereby maintaining the wide ESW of concentrated electrolytes while retaining the rate performance and temperature tolerance of dilute systems. By electrochemically forming a thin artificial solid–electrolyte interphase (ASEI) on carbon electrodes, the hydrogen evolution reaction onset is cathodically shifted by ~0.3 V in a moderately concentrated electrolyte. Symmetric cells with ASEI layers operated stably at 1.7 V in a dilute electrolyte (5 m NaClO4). ASEI cells with diulte electrolytes preserve 80 % capacitance at 50 A g−1 (vs 0.5 A g−1), whereas WiSEs counterparts fall below 50 %. The advantage of ASEI application is even more pronounced at −20 °C. This work establishes a pathway to aqueous supercapacitors that combines high voltage, fast kinetics, and low-temperature performance.

키워드