High-performance Ti3C2Tx achieved by polyaniline intercalation and gelatinization as a high-energy cathode for zinc-ion capacitor

The actual manufacture of supercapacitors (SCs) is restricted by the inadequate energy density, and the energy density of devices can be properly promoted by assembling zinc-ion capacitors (ZICs) which used capacitive cathode and battery-type anode. Two-dimensional (2D) MXene has brought great focuses in the electrode research on the foundation of large redox-active surface, but the specific capacitance is still affected by the tight stacking of interlaminations. Ti3C2Tx@polyaniline (PANI) heterostructures are prepared by uniformly depositing the conductive polymer PANI nanorods as the intercalation agent into the external of Ti3C2Tx nanosheets to inhibit stacking. Subsequently, by using graphene oxide (GO)-assisted low-temperature hydrothermal self-assembly manufacture, 2D heterostructures are assembled into the three-dimensional (3D) porous crosslinked Ti3C2Tx@PANI-reduced graphene oxide (RGO) hydrogels. Attributed to the synergistic work of PANI nanorods, Ti3C2TX nanosheets, and 3D crosslinking frameworks of RGO to match capacitive and battery effects, 3D porous hierarchical Ti3C2Tx@PANI-RGO heterostructure hydrogels have rich ion transport channels, a large number of active sites, and excellent reaction kinetics. ZIC is assembled by using Ti3C2Tx@PANI-RGO heterostructure hydrogels as cathodes and zinc foil as anodes. In this work, Ti3C2Tx@PANI-RGO//Zn ZIC exhibits a wide working window (2.0 V), marked specific capacitance (589.89 F.g(-1) at 0.5 A.g(-1)), salient energy density (327.71 Wh.kg(-1) at 513.61 W.kg(-1) and 192.20 Wh.kg(-1) at 13,005.87 W.kg(-1)), and durable cycling stability (97.87% capacitance retention after 10,000 cycles at 10 A.g(-1)). This study emphasizes the device design of ZICs and the broad prospect of Ti3C2Tx-based hydrogels as viable cathodes for ZICs.