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

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.

Automated summary

This study presents a scalable approach to improve the electrochemical properties of aqueous zinc ion hybrid capacitors (ZIHCs) by addressing the deficiencies related to the Zn-anode/electrolyte interface and cathode materials. The use of a modified electrolyte and an oxygen-rich 3D MGC cathode resulted in high specific energy and power capability, as well as excellent cycling durability. These findings contribute to the practical application of highly efficient ZIHCs.