Self-Assembled MXene/Polyaniline Gels Enable 3D-Printed Micro-Supercapacitors with High Energy Storage

The rapid development of wearable and flexible electronics has imposed stringent demands on portable energy storage devices, requiring both high energy density and facile structural processability. Therefore, developing direct ink writing (DIW) printable polyaniline (PANI)-based micro-supercapacitors (MSCs) with high charge storage capability is of great significance. However, current printable PANI electrodes often suffer from low active mass loading and poor charge transport, severely limiting their practical application. Herein, we report a solvent-assisted self-assembly strategy combined with DIW 3D printing to fabricate MXene/PANI composite gel electrodes for high-performance MSCs. A molecularly homogeneous MXene/PANI composite was obtained via spontaneous desolvation-driven self-assembly, forming a hierarchical 3D porous network where PANI nanoparticles intercalate between MXene nanosheets as conductive bridges. The resulting MXene/PANI gel ink exhibits excellent printability, high viscosity and shape fidelity, enabling precise DIW printing of thick, high-mass-loading electrodes. Benefiting from its integrated 3D conductive network and efficient ion diffusion pathways, the electrode achieves a high specific capacitance of 264.5 F g–1, 84% retention at 10 A g–1, and 96.8% capacitance retention after 6000 cycles. The quasi-solid-state MSCs deliver an ultrahigh areal capacitance of 2950 mF cm–2, an energy density of 331.9 μWh cm–2, and a power density of 9 mW cm–2. This work establishes a scalable route for designing high-loading pseudocapacitive electrodes via DIW 3D printing for next-generation miniaturized energy storage systems.