Flexible Quasi‐Solid‐State High‐Performance Aqueous Zinc Ion Hybrid Supercapacitor with Water‐in‐Salt Hydrogel Electrolyte and N/P‐Dual Doped Graphene Hydrogel Electrodes

Abstract Aqueous zinc ion hybrid supercapacitors (ZHSCs) have attracted considerable attention owing to the bivalent nature, high abundance, and stability in the water‐based system of zinc. High energy density and superb power output can be achieved simultaneously by integrating a battery‐type electrode and a capacitive‐type electrode. However, there are still many issues that remain, including but not only hydrogen evolution reaction, dendrite growth, and dramatic capacity loss at low temperatures. Herein, a new type of hybrid “water‐in‐salt” hydrogel electrolyte based on 1 m Zn(CH₃COO)₂ and 20 m CH₃COOK to expand the voltage window of ZHSCs to 0–2.1 V by suppressing the decomposition of water molecules is developed. The aqueous ZHSC delivers maximum energy of 100.2 Wh kg⁻¹ at a power density of 487.5 W kg⁻¹ based on the active materials and displays excellent cycling stability with 99.5% capacitance retention after 4000 cycles. Meanwhile, it is found that the assembled flexible quasi‐solid‐state ZHSC using the potassium polyacrylate/sodium carboxymethyl cellulose hydrogel electrolyte (containing 1 m Zn(CH₃COO)₂ and 20 m CH₃COOK) also shows high‐performance (energy density of 106.5 Wh kg⁻¹ at a power density of 383.3 W kg⁻¹) with temperature adaptability at low temperature and wearable application potential with excellent energy storage performance.