Polyacrylamide-based hydrogel electrolyte for modulating water activity in aqueous hybrid batteries

While zinc-ion and hybrid aqueous battery systems have emerged as potential substitutes for expensive lithium-ion batteries, issues like side reactions, limited electrochemical stability, and electrolyte leakage hinder their commercialization. Due to their low cost, high stability, minimal leakage risks, and a wide variety of modification opportunities, hydrogel electrolytes are considered the most promising solution compared to liquid or solid electrolytes. Here, we synthesized a dual-function hydrogel electrolyte based on polyacrylamide and poly(ethylene dioxythiophene):polystyrene (PPP). This electrolyte reduces water content and enhances stability by minimizing side reactions while swelling in a binary ethylene glycol and water solution (EG 10%) further stabilizes the 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. The PPP-based system reached a value of 119.2 mA g⁻¹, while the aqueous electrolyte reached only 80.4 mA g⁻¹ specific capacity. The rechargeable PPP hydrogel electrolyte-based hybrid aqueous battery with zinc anode achieved more than 600 cycles. Coulombic efficiency (CE) remained at 99%, indicating good electrochemical reaction stability and reversibility. 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. 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.