Enhanced Low-Temperature Durability of Flexible Zinc–Air Batteries Using NaCl-Doped Dual-Network Hydrogel Electrolytes

With the rapid development of flexible wearable devices, the demand for advanced energy storage systems has significantly increased. Flexible zinc–air batteries (ZABs) are promising candidates due to their low cost and high energy density. However, their performance in low-temperature environments has been a significant challenge. In this study, we introduce a dual-network hydrogel electrolyte composed of sodium polyacrylate and polyacrylamide (PANa-M), further enhanced with sodium chloride (NaCl) to form PANa-M–NaCl. The inclusion of NaCl significantly strengthens the hydrogel’s mechanical durability, enabling it to withstand extreme conditions like bending, twisting, and squeezing. Beyond its structural benefits, NaCl also enhances the hydrogel’s low-temperature performance by improving water retention, accelerating electrochemical reaction kinetics, and lowering the electrolyte’s freezing point. Moreover, NaCl mitigates side reactions on the zinc electrode, further stabilizing battery operation under harsh conditions. As a result, PANa-M–NaCl-based ZABs demonstrate a power density of 85.3 mW/cm 2 and sustain a charge–discharge cycle life exceeding 105 h at room temperature. More importantly, at −30 °C, the ZABs maintain excellent performance with over 250 h of charge–discharge cycles, highlighting the effectiveness of NaCl in improving electrolyte concentration and stabilizing the gel structure at subzero temperatures. This study presents a simple and effective strategy to enhance the durability and performance of flexible ZABs in challenging low-temperature environments, paving the way for broader applications in wearable technology.