Adv. Funct. Mater. - 3D-Printed Dual-Gradient Gel Electrodes Synchronize Ion Transport and Active-Site Utilization for High-Energy Zinc-Ion Hybrid Supercapacitors

Jian Meng^#, Wenhui Tai^#, Tong Zhou^#, Mai Chen, Le Li*, and Tianxi Liu*

Advanced Functional Materials 2026, DOI: 10.1002/adfm.78804

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.

Link: https://doi.org/10.1002/adfm.78804