How Entropy of Electrolytes Effects Aqueous Rechargeable Zinc Metal Batteries: A Review

Aqueous rechargeable zinc metal batteries (ARZMBs) have attracted increasing attention as sustainable energy storage systems capable of mitigating the intermittency of renewable energy, due to their high safety, low cost, and environmental friendliness. However, their practical applications are still hindered by several critical issues, including poor low-temperature performance, slow ion diffusion of the electrolytes, and severe gas generation reaction at the interface between the electrolyte and the electrode. In recent years, the design concept of high-entropy electrolytes (HEEs) has been introduced into aqueous energy storage systems. By introducing diverse ions or solvent molecules, it is possible to enhance the entropies of the system, including configurational, tetrahedral, and mixing entropy, thereby enabling control over the solvation structure, hydrogen bond network, and interfacial reactions. However, the concept of entropy remains relatively abstract and challenging for newcomers to grasp. Moreover, the performance enhancements achievable through different types of entropy vary considerably, and a systematic review comparing these effects is currently lacking. This work reviews the fundamental principles of HEEs, strategies for entropy modulation, and recent advances in their applications for ARZMBs. Special emphasis is placed on the mechanisms by which configurational entropy optimizes the Zn²⁺ solvation structure, as well as the role of tetrahedral entropy in modulating the hydrogen bond network. Finally, we discuss the challenges and future directions for HEEs in the development of high-performance, wide-temperature-range, and long-lifespan ARZMBs, with the aim of providing theoretical guidance to advance green energy storage technologies.