Engineering Polyacrylamide‐Based Hydrogel Electrolytes for Zn‐Ion Batteries: A Functional Modification Framework Bridging Mechanisms and Performance

ABSTRACT Aqueous Zn‑ion batteries (ZIBs) are attractive for their safety and cost‑effectiveness, but Zn anode instability and side reactions hinder their practical development. In this context, constructing polyacrylamide (PAM)‑based hydrogel electrolytes has emerged as a compelling strategy to address these issues. Nonetheless, pristine PAM hydrogels are often constrained by limited ionic conductivity, inadequate mechanical strength, and suboptimal interfacial stability, motivating the exploration of diverse functional modification strategies. Herein, this review presents the first systematic overview of recent advances in the functional modification of PAM‑based hydrogel electrolytes for ZIBs. We systematically elucidate the scientific mechanisms underlying key design approaches, including hydrogen‑bond network modulation, multifunctional network construction, functional additive/filler incorporation, and functional group modification. These mechanisms are driven centrally by hydrogen bond competition, electrostatic repulsion, and coordination effects. The impact of these strategies on critical battery performance metrics, such as ion transport behavior, mechanical flexibility, and wide‑temperature adaptability, is then comprehensively assessed. Subsequently, we offer a forward‑looking perspective on remaining challenges and future directions. Collectively, this review consolidates advances in PAM‑based hydrogel electrolytes, establishing a solid theoretical foundation and providing innovative insights for the rational design and fabrication of next‑generation flexible ZIBs that synergistically integrate high performance, enhanced safety, and prolonged cycle life.