High-energy flexible solid-state supercapacitors based on O, N, S-tridoped carbon electrodes and a 3.5 V gel-type electrolyte

Developing advanced electrodes and electrolytes are two basic strategies to boost the energy outputs of supercapacitors, but previous studies are generally constrained to the point where only one component is focused. Herein, we report the design of high-performance O, N, S-tridoped carbon (ONSC) electrodes and a high-voltage porous gel electrolyte to construct high-energy flexible solid-state supercapacitors. First, high-surface-area (2917 m2 g−1) ONSCs with enriched heteroatoms (14.85 wt%) are synthesized based on a novel and simple benzoquinone-thiourea route to achieve a superior electrochemical capacitive capability. Second, a highly porous gel polymer is utilized to support ionic liquid of 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4) for fabricating a 3.5 V ionogel electrolyte. The elaborated ONSC electrode and EMIMBF4 gel electrolyte enable the resultant solid-state supercapacitor with an extremely energy supply of 90.9 Wh kg−1, along with excellent cyclability (91.6% over 10,000 cycles) and temperature robustness (0–80 °C). Besides, an assembled flexible solid-state device delivers an energy density of 76.6 Wh kg−1, and manifests high flexibility with 90% retention even under a bending angle of 180°. This work presents an electrode/electrolyte engineering principle to achieve highly efficient energy storage.