The critical role of water molecules in the development of aqueous electrolytes for rechargeable metal-ion batteries

Abstract

Aqueous rechargeable metal ion batteries (AMIBs) have emerged as a promising option for large-scale electrical energy storage due to their environmental friendliness, low cost, and high safety. This review examines the latest advanced technology orientation for AMIB electrolytes from these perspectives: (1) dilute to high concentrations, (2) room temperature to extreme temperatures, and (3) liquid to quasi-solid states. Typically, the significant impact of water molecule content on the solvation sheath, SEI formation, and enhancement of electrochemical performance in high concentration electrolytes was thoroughly reviewed and discussed. Furthermore, the utilization of salt concentration, organic additives, and hydrogel electrolytes was explored in breaking and re-forming hydrogen bonds between water molecules, with the aim of improving the low temperature performance of water electrolytes. Additionally, we also focus on the storage of water molecules within hydrophilic matrices, leading to advancements in the transition of water electrolytes from a liquid state to a quasi-solid state. This review provides insights into current research directions for aqueous electrolytes and an emphasis on the crucial role played by water molecules in this process.