High-performance Zn-ion hybrid supercapacitor based on 3D K+-intercalated Ti3C2TX hydrogel cathode

Aqueous zinc-ion hybrid supercapacitors (ZHSCs) exhibit great potential for energy storage and conversion devices, owing to their inherent safety and cost-effectiveness. Nevertheless, the structure of traditional porous carbon cathodes hinders the zinc-ion diffusion kinetics, rendering the energy densities of conventional ZHSCs uncompetitive and severely impeding their practical applications. 2D transition metal carbides/nitrides, known as MXenes, exhibit excellent conductivity and abundant surface functional groups, qualifying them as ideal candidates for constructing high-capacity cathodes in high-performance ZHSCs. This study presents the fabrication of a ZHSC utilizing 3D porous K + -intercalated Ti 3 C 2 T X -reduced graphene oxide (K + -Ti 3 C 2 T X -RGO) hydrogel as cathode, paired with a zinc foil as anode. Upon treatment with KOH solution, Ti 3 C 2 T X undergoes K + ion intercalation into its nanosheets, resulting in partial elimination of terminal -F groups and expansion of the MXene interlayer spacing. Subsequently, large-scale graphene oxide (GO) was employed as a conductive binder to interconnect the intercalated multilayer Ti 3 C 2 T X , and a reducing agent was incorporated to facilitate self-assembly into a hydrogel. This approach augmented the accessibility of ions and facilitated their transport within the resultant structure. The ZHSC, fabricated with this composite cathode, synergistically integrates the supercapacitor’s high-power density and the battery’s high energy density. The results indicate that the ZHSC exhibited excellent electrochemical performance, featuring a high specific capacitance of 253.86 F g −1 at 1 A g −1 and an impressive energy density of 141.03 Wh kg −1 at 999.99 W kg −1 . Notably, after 5000 charge-discharge cycles at 10 A g −1 , the ZHSC maintained a capacitance retention rate above 87.96 %, highlighting its exceptional cycling stability.