Dual cross-linked hydrogel electrolyte modified by nonionic surfactant for flexible and rechargeable zinc-air battery

Flexible zinc-air batteries (ZABs) have gained much more attention due to their high specific capacity, low cost and safety. However, conventional hydrogel electrolytes exhibit poor mechanical properties and unstable structures. Herein, we developed a series of dual cross-linked high-performance hydrogel electrolytes for flexible and rechargeable batteries, which were prepared by acrylamide (AM), cellulose nanofibers (CNFs), dextran (DEX), polyethylene glycol of average molar weight 400 (PEG400). The DEX and epichlorohydrin (ECH) reactions established the second crosslinking network. Benefiting from the unique chemical structure and the incorporation of PEG400, the hydrogel electrolyte exhibited high ionic conductivity of 315 mS cm- 1, excellent mechanical strength, and superior water retention capacities. The fabricated flexible ZABs delivered a long discharge time of 56 h and a long cycling lifetime of 72 h. In addition, the battery retained excellent electrochemical properties over a wide operating temperature range (-20 degrees C to 60 degrees C) and had satisfactory environment adaptability in severe conditions. Furthermore, two ZABs connected in series provided continuous power to Light Emitting Diode (LED) and electronic timers in harsh environments. However, ZABs prepared with conventional hydrogel electrolytes demonstrate a short cycling lifetime and bad practicality under extreme environments. This study provides a novel strategy for preparing and optimizing hydrogel electrolytes and can promote the development of ZABs to be adopted in various scenarios.