Performance degradation and mitigation strategies of hydrogel-based zinc-ion batteries: A review

Abstract

Hydrogel zinc ion batteries (HZIBs) represent a cutting-edge advancement in energy storage systems, leveraging the exceptional properties of hydrogels, including superior mechanical flexibility and robust structural stability. Despite their promising attributes, HZIBs face persistent challenges that hinder their practical deployment, notably performance degradation during long-term cycling. In this review, we provide a comprehensive explanation of the fundamental structure and working principles of HZIBs, analyzing the roles of each component. We then systematically explore these degradation mechanisms and comprehensively summarize the key influencing factors, including zinc dendrite formation, hydrogel matrix degradation, electrolyte depletion, and interfacial instability. The role of environmental and operational factors, such as temperature fluctuations and humidity variations, in exacerbating these degradation processes is also highlighted. Recent material engineering strategies to mitigate these issues are summarized: 1) the development of structurally reinforced hydrogel electrolytes; 2) the use of functional additives for ion transport regulation; and 3) interfacial engineering for uniform zinc deposition. Moreover, emerging fabrication techniques, such as nanoscale structural design and additive manufacturing, are discussed for their potential to optimize the mechanical robustness and electrochemical performance of HZIBs. This review integrates fundamental insights with advanced engineering approaches to provide practical guidance for the scalable development of high performance HZIBs for flexible and wearable applications.