A flexible, high-energy density, and temperature-tolerant asymmetric supercapacitor based on water-in-salt gel electrolyte

The dramatic development of wearable electronics has led to extensive research into flexible super -capacitors as wearable energy storage devices. The practical application of supercapacitors to wearable electronics requires improved temperature tolerance and high energy density. Herein, we report the fab-rication of a high-voltage flexible aqueous supercapacitor featuring high energy density and a wide oper-ating temperature range. This is achieved by the strategy of simultaneously utilizing asymmetric electrodes and water-in-salt gel electrolyte (WISGE). Using NaClO4-based WISGE and asymmetric electrodes consisting of Na-inserted MnO2 and N-doped carbon nanofibers, we obtain excellent electrochemical performance, including a gravimetric capacitance of 97.2 F g-1, energy density of 90 Wh kg-1, power density of 28.1 kW kg-1, operation voltage window of 2.6 V, and capacitance retention of 85.2% over 10,000 charge/ discharge cycles. The fabricated flexible supercapacitor is stable under repeated temperature changes be-tween - 20 and 80 & DEG;C, regardless of bending deformation. After three cycles of cooling and heating, the initial capacitance at room temperature is 95.1% recovered. This study demonstrates the potential appli-cation of our high-performance flexible aqueous supercapacitors to wearable devices, given their resistance to changes in environmental temperature and mechanical deformation. & COPY; 2023 Elsevier B.V. All rights reserved.