Ternary-doped carbon electrodes for advanced aqueous solid-state supercapacitors based on a “water-in-salt” gel electrolyte

Abstract

The key concern in constructing high-energy supercapacitors is maximizing the electrode capacitance and the cell voltage. However, the current research usually addresses this issue by designing advanced electrodes or seeking high-potential electrolytes separately, instead of both. Herein, we demonstrate a two-pronged design of ternary-doped carbon electrodes and a high-voltage “water-in-salt” (WIS) gel electrolyte to support advanced aqueous-based solid-state supercapacitors. The fabrication of N/S/O multidoped carbons is quite straightforward, involving a facile benzoquinone/sulfourea polymerization and a common carbonization/activation procedure, which avoid sophisticated technique/conditions and/or time-consuming synthetic routes. The carbons feature an extraordinary surface area, high content of heteroatoms, and improved surface wettability. A highly porous gel polymer is introduced as a supporting matrix for the WIS to design a 2.3 V gel-type electrolyte, in pursuit of a new record high-energy aqueous solid-state supercapacitor of 37.7 W h kg⁻¹, with excellent temperature robustness in the range of 0–80 °C. Furthermore, an assembled flexible device delivers a stable energy output of 34.3 W h kg⁻¹ and demonstrates great flexibility with 91.6% energy retention even in a bending state of 180°. This study presents an electrode/electrolyte cooperative effect to unlock the energy potential of aqueous flexible solid-state supercapacitors.