Polyacrylamide-Based Hydrogel Electrolyte for Modulating Water Activity in Aqueous Zinc-Ion Batteries

Abstract

The limitations of lithium-ion battery systems, including lithium scarcity, demanding assembly conditions, and safety risks associated with flammable organic electrolytes, underscore the need for renewable, cost-effective, and safe alternatives. While zinc-ion or hybrid aqueous battery systems have garnered interest, challenges such as undesired side reactions, limited electrochemical stability, and electrolyte leakage persist, hindering large-scale adoption. Among electrolyte engineering approaches, hydrogel electrolytes have emerged as promising solutions, offering improved stability and relatively high ionic conductivity while mitigating leakage risks. Additionally, the modification opportunities of the hydrogel electrolytes present great potential for various applications. Here, we synthesized a dual-function hydrogel electrolyte based on polyacrylamide and poly(ethylene dioxythiophene):polystyrene. This electrolyte effectively reduces water content and enhances stability by minimizing undesired side reactions. Moreover, the polymer network and its functional groups promote controlled ion transport. Swelling in a binary solution of ethylene glycol and water (EG 10%) further enhances the stability of the assembled battery system. The developed hydrogel exhibits relatively good ionic conductivity (1.6 * 10-3 S cm-1) and excellent electrochemical stability, surpassing 2.5 V on linear sweep voltammetry tests (Figure 1). An assembled aqueous lithium-ion hybrid battery with a zinc anode demonstrates high capacity (119.2 mAh g-1), close to 100% columbic efficiency, and good cycle stability, retaining 67.6% capacity after more than 380 cycles. This study highlights the potential of polyacrylamide-based hydrogel electrolytes with dual functionality as the electrolyte and separator, inspiring further development in hydrogel electrolytes for aqueous battery systems. Acknowledgement BR21882402 "Development of new material technologies and energy storage systems for a green economy" from the Ministry of Science and Higher Education of the Republic of Kazakhstan. Figure 1