Dual-Interfacial Engineering Enabled by a Zn²⁺-Induced Self-Assembled Hydrogel Electrolyte Toward Flexible On-Body Zinc-Iodine Batteries.

Abstract

Aqueous zinc-iodine batteries (AZIBs) are promising candidates for flexible electronics owing to their intrinsic safety. Nevertheless, their practical deployment is impeded by severe interfacial challenges, including polyiodide shuttling, zinc (Zn) dendrite growth, and parasitic reactions. Herein, a Zn² ⁺-induced molecular self-assembly strategy based on natural glycyrrhizic acid (Gl) is proposed to construct a robust dual-network hydrogel electrolyte. The self-assembled Gl nanofibrous network can simultaneously and effectively regulate the dual electrode/electrolyte interfaces. At the anode interface, the Gl nanofibrous network adsorbed on the Zn surface enables homoepitaxial Zn plating, promoting uniform Zn nucleation and growth. At the cathode interface, the p-π conjugated structure and nanofibrous network of Gl cooperatively immobilize polyiodides, effectively suppressing the shuttle effect. Consequently, the Zn||Zn symmetric cell exhibits excellent cycling stability over 1900 h at 1 mA cm^-2 with 1 mAh cm^-2. The Zn||I₂ pouch cell achieves a long lifespan with a high-capacity retention of 78.1% and a low N/P ratio of 1.93. Moreover, leveraging the high biocompatibility and flexibility of this self-assembled hydrogel, an on-body transcranial direct current stimulation (tDCS) device integrated with the Zn||I₂ battery delivers a stable 1.5 mA current for therapeutic neuromodulation, demonstrating a feasible pathway for flexible on-body AZIBs.