Synergistic Coordination Regulation and Nanofiller-Guided Ion Transport in a Polyacrylamide Gel Electrolyte for Highly Reversible Aqueous Zn Metal Anodes

Abstract

Despite their safety and cost advantages, aqueous zinc-ion batteries remain limited by the instability of Zn metal anodes, including nonuniform deposition, dendrite growth, and parasitic reactions. A PAM/CMC-Na/CNTs (PCC) hydrogel electrolyte is constructed by incorporating sodium carboxymethyl cellulose (CMC-Na) and carbon nanotubes (CNTs) into a polyacrylamide (PAM) matrix. The –COO– and –OH groups of CMC-Na regulate the local coordination environment of Zn2+ and suppress water-related side reactions, while CNTs reinforce the gel network and improve interfacial contact. PCC exhibits an ionic conductivity of 24.16 mS cm–1 and an apparent Zn2+ transference number of 0.791. These transport characteristics, together with interfacial analyses, are consistent with more uniform Zn deposition. Zn//Zn symmetric cells cycle stably for over 2300 h at 1 mA cm–2 with an areal capacity of 1 mAh cm–2 and for approximately 550 h at 5 mA cm–2 with a capacity of 5 mAh cm–2. Zn//Cu cells achieve an average Coulombic efficiency of 99.94%, while Zn//MnO2 full cells retain 81.64% capacity after 700 cycles at 1 A g–1. A high-loading Zn//MnO2 pouch cell further demonstrates favorable energy-storage performance. This work presents a strategy for designing hydrogel electrolytes that integrate coordination regulation, homogenized ion transport, and mechanical robustness.