Water molecules regulation for reversible Zn anode in aqueous zinc ion battery: Mini-review

With the low cost, excellent safety and high theoretical specific capacity, aqueous zinc-ion batteries (AZIBs) are considered as a potential rival for lithium-ion batteries to promote the sustainable development of large-scale energy storage technologies. However, the notorious Zn dendrites and low Coulombic efficiency (CE) limit further development of AZIBs, due to the unstable electrochemical deposition/stripping behavior of Zn anode in aqueous zinc ion electrolytes. In this review, critical issues and advances are summarized in electrolyte engineering strategies. These strategies are focused on active water molecules during electrochemical process, including high-concentration electrolytes, ionic liquids, gel-polymer electrolytes and functional additives. With suppressed active water molecules, the solvation and de-solvation behavior of Zn2+ can be regulated, thereby modulating the electrochemical performance of Zn anode. Finally, the inherent problems of these strategies are discussed, and some promising directions are provided on electrolytes engineering for high performance Zn anode in AZIBs.