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

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.

Automated summary

A new hybrid water-in-salt hydrogel electrolyte has been developed to expand the voltage window of ZHSCs, achieving high energy density and excellent cycling stability. Additionally, a flexible quasi-solid-state ZHSC using this electrolyte shows high performance and potential for wearable applications.