Enabling High‐Performance Zn Anodes Through Nitrogen‐Participated p–π Conjugation in Hydrogel Electrolytes

Abstract Although hydrogel electrolytes can alleviate dendrite growth and side reactions on the Zn anodes of aqueous Zn metal batteries, they still need improvements due to unsatisfying ionic conductivities and mechanical properties. Herein, inspired by antidiabetics, metformin hydrochloride containing nitrogen‐participated p‐π conjugation is employed to enhance polyacrylamide (PAM) hydrogel electrolytes. In electrolyte, metformin cation (MFH⁺) reforms hydrogen bond networks and reconstructs Zn²⁺ solvation structure by O−H…π interactions, reducing chemical activity of free H₂O and accelerating Zn²⁺ desolvation process. Meanwhile, the p‐π conjugation enables MFH⁺ to interconnect PAM chains and stabilize SO₄²⁻, improving the mechanical property and Zn²⁺ conductive efficiency of the electrolyte. At the electrolyte‐electrode interface, the p‐π conjugation induces MFH⁺ to adsorb on the Zn(002) plane and reconstruct electric field, and an MFH⁺‐derived solid electrolyte interphase forms on the Zn anode, uniformizing dendrite‐free Zn²⁺ deposition and inhibiting side reactions. Consequently, the Zn//Zn cells demonstrate superior cycling stability for over 3200 h at 1 mA cm⁻² and over 500 h at 76.95% depth‐of‐discharge, with a good wide temperature performance. The pouch cell with a high mass loading (20 mg cm⁻²) provides a maximum capacity of 444.7 mAh under 200 mA g⁻¹ over 60 cycles, showing good prospects for practical use.