High-performance Ti₃C₂T_x 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. Ti₃C₂T_x@polyaniline (PANI) heterostructures are prepared by uniformly depositing the conductive polymer PANI nanorods as the intercalation agent into the external of Ti₃C₂T_x 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 Ti₃C₂T_x@PANI-reduced graphene oxide (RGO) hydrogels. Attributed to the synergistic work of PANI nanorods, Ti₃C₂T_X nanosheets, and 3D crosslinking frameworks of RGO to match capacitive and battery effects, 3D porous hierarchical Ti₃C₂T_x@PANI-RGO heterostructure hydrogels have rich ion transport channels, a large number of active sites, and excellent reaction kinetics. ZIC is assembled by using Ti₃C₂T_x@PANI-RGO heterostructure hydrogels as cathodes and zinc foil as anodes. In this work, Ti₃C₂T_x@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 Ti₃C₂T_x-based hydrogels as viable cathodes for ZICs.