High energy superstable hybrid capacitor with a self‐regulated Zn/electrolyte interface and 3D graphene‐like carbon cathode

Abstract Rechargeable aqueous zinc ion hybrid capacitors (ZIHCs), as an up‐and‐comer aqueous electrochemical energy storage system, endure in their infancy because of the substandard reversibility of Zn anodes, structural deterioration of cathode materials, and narrow electrochemical stability window. Herein, a scalable approach is described that addresses Zn‐anode/electrolyte interface and cathode materials associated deficiencies and boosts the electrochemical properties of ZIHCs. The Zn‐anode/electrolyte interface is self‐regulated by alteration of the traditional Zn2+ electrolyte with Na‐based supporting salt without surrendering the cost, safety, and green features of the Zn‐based system which further validates the excellent reversibility over 1100 h with suppressed hydrogen evolution. The deficits of cathode materials were overcome by using a high‐mass loaded, oxygen‐rich, 3D, multiscaled graphene‐like carbon (3D MGC) cathode. Due to the multiscaled texture, high electronic conductivity, and oxygen‐rich functional groups of 3D MGC, reversible redox capacitance was obtained with a traditional adsorption/desorption mechanism. Prototype ZIHCs containing the modified electrolyte and an oxygen‐rich 3D MGC cathode resulted in battery‐like specific energy (203 Wh kg−1 at 1.6 A g−1) and supercapacitor‐type power capability (4.9 kW kg−1 at 8 A g−1) with outstanding cycling durability (96.75% retention over 30 000 cycles at 10 A g−1). These findings pave the way toward the utilization of highly efficient ZIHCs for practical applications.