Current status and technical challenges of electrolytes in zinc–air batteries: An in-depth review

•A brief summary of challenges and underlying opportunities was expressed.•This paper highlights issues related to employ liquid electrolytes in ZABs.•Various suggestions to reduce dendrites formation and ZnO layer was presented.•Additives demonstrate as promising approach for liquid and polymer electrolytes. In the past few years, there has been a growing level of interest in the research and development of energy storage systems such as batteries. This is a direct consequence of the soaring rise in global energy demand across various commercial and industrial sectors. Lithium ion batteries have set out a feasible horizon for widespread deployment as small-scale energy storage devices due to their high efficiency and cyclability. However, the availability and cost of lithium have limited the commercial deployment of large-scale systems. On the other hand, zinc-air batteries have demonstrated comparable efficiencies and have been reported to be suitable replacements for lithium batteries in large-scale applications. Nevertheless, more research has been undertaken to address the issues associated with the cycling processes of these batteries. Secondary zinc-air batteries are yet to be commercially proven feasible due to the low charge/discharge cycle life of electrodes. The main problems of secondary alkaline zinc–air batteries are dendritic growth resulting in an alternation of morphology and structure, self-dissolutionand the consequent occurrence of hydrogen evolution reactions. However, by and large, inefficient electrolytes are the main culprits responsible for the reduced performance of zinc-air batteries. Therefore, a comprehensive review of current advancements in the development of suitable electrolytes to promote zinc-air batteries towards commercial application will provide a perspective for future rechargeable zinc-air batteries. In this in-depth review, the effects of the types of electrolytes and their properties on the electrochemical performance of Zn anode have been discussed. A demonstration of the current research status and challenges set upon the large-scale deployment of zinc-air batteries will facilitate the educated steering of future research directions in this critically important realm.