3D‐Printed Dual‐Gradient Gel Electrodes Synchronize Ion Transport and Active‐Site Utilization for High‐Energy Zinc‐Ion Hybrid Supercapacitors

ABSTRACT High‐mass‐loading gel electrodes are critical for practical zinc‐ion hybrid supercapacitors, but sluggish ion penetration and depth‐dependent reaction heterogeneity hinder their performance. Herein, we report a dual‐gradient MXene/polypyrrole@Carbon nanotube gel composite thick electrode via stepwise multi‐ink 3D printing. The architecture couples a microlattice grid‐spacing gradient with an intra‐filament pore‐structure gradient, enabling coordinated regulation of macroscopic ion access and electroactive‐site availability across the electrode thickness. The electrolyte‐facing region combines larger microlattice openings with lower micron‐scale porosity but higher specific surface area, whereas the current‐collector side features smaller openings, higher micron‐scale porosity, and coarser transport pores. X‐ray micro‐computed tomography verifies the continuous three‐dimensional gradient architecture, while COMSOL simulations reveal suppressed concentration polarization and homogenized reaction‐current distribution. The electrode retains 71.1% capacitance under a 40‐fold current‐density increase and 98.8% capacitance after 15000 cycles. Pouch‐type devices achieve 6.2 F cm −2 and 0.86 mWh cm −2 at 42.7 mg cm −2 , providing a scalable design framework for high‐energy flexible energy storage.