Energy Storage Chemistry in Aqueous Zinc Metal Batteries

Abstract

Aqueous zinc metal batteries (ZMBs) are considered promising candidates for large-scale energy storage. However, there are still some drawbacks associated with the cathode, zinc anode, and electrolyte that limit their practical application. In this Focus Review, we focus on unveiling the chemical nature of aqueous ZMBs. First, cathode materials and electrochemical reactions are summarized and discussed. Then, fundamental understanding of zinc plating/stripping chemistry is presented, followed by the principle of zinc-dendrite growth and hydrogen evolution as well as the corresponding mitigation strategies. After that, electrolyte engineering, mainly considering salts, concentration, additives, and hydrogel electrolyte, is discussed. Finally, the remaining challenges of aqueous ZMBs toward practical application are noted, mainly including the undefined mechanism and dissolution of the cathode, dendrite growth and hydrogen evolution of the zinc anode, equilibrium between performance and cost of the electrolyte, and testing protocols of full cells. This Focus Review provides new insights for further research and development of aqueous ZMBs.