Mitigating Diffusion-Limited Concentration Polarization via Intrinsic Electrocapillary Effects in Engineered Hollow Cathodes.

Abstract

Aqueous zinc-ion batteries (AZIBs) are promising for grid-scale energy storage but suffer from sluggish ion diffusion kinetics, severe concentration polarization, and rapid performance decay. While structural engineering offers partial mitigation, a more fundamental solution lies in actively controlling interfacial mass transport. Herein, we overcome this issue by harnessing the electrocapillary effect using sea urchin-like MnO₂ microspheres with hollow nanotubes (H-MnO₂). This nanocapillary network enables rapid ion replenishment at the reaction interface, effectively suppressing concentration polarization. As a result, H-MnO₂ cathode exhibits enhanced wettability, a lower ion adsorption energy barrier, and significantly accelerated Zn²⁺/H⁺ diffusion kinetics. Consequently, the Zn||H-MnO₂ battery achieves a high capacity of 407 mAh g^-1 at 0.1 A g^-1 and stable cycling with over 200 mAh g^-1 after 350 cycles at 0.5 A g^-1. This work transcends conventional structural optimization by introducing electrocapillary management as a new design paradigm for high-performance electrochemical energy storage.