Low-temperature resistant gel polymer electrolytes for zinc-air batteries

The rapid development of wearable devices has put forward high requirements for stable, solid-state, flexible and even stretchable energy storage systems. Owing to their high specific energy density and volumetric energy density, metal-air batteries especially high-safety zinc-air batteries (ZABs), have attracted widespread attention. However, limited by the reduced ionic conductivity of electrolyte and the sluggish kinetics of oxygen reduction/evolution reactions at the air cathode during discharge/charge processes below 0 degrees C, the performances of ZABs severely deteriorate. Rationally designed gel polymer electrolytes (GPEs) not only offer superior mechanical performance but also provide ZABs with accelerated ion transport to boost electrochemical performance at low temperatures. Herein, the types of GPEs towards electrochemical energy systems are first summarized. And then, the research toolbox for GPEs and assembled ZABs is put forward. Next, the design strategies for low-temperature tolerant GPEs in ZABs are highlighted, such as introduction of organic solvents, alkalization of hydrogel electrolytes, construction of double-network electrolytes, etc. Finally, current challenges and perspectives are proposed. This review provides up-to-date insights on the rational design of GPEs for ZABs, which can be expanded to other metal-air batteries, metal-sulfur batteries, metal-ion batteries and so on.