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

Abstract 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-dissolution and 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.