Entropy-regulated electrolytes for improving Zn2+ dynamics and Zn anodes reversibility

Abstract

Entropy-regulated electrolytes exhibit improved performance exceeding traditional liquid systems. Despite their potential merits, the impacts of entropy on thermodynamics and kinetic properties of the electrolyte have remained elusive. A specially designed entropy-regulated Zn-salt electrolyte (ERE) with multiple halogen anions (Cl−, Br−, and I−) is proposed here to discuss the correlation between locally excess entropy and diffusion properties. Owing to the higher pair-correlated entropy of the ERE compared to single-anion systems, it can greatly facilitate the Zn2+ transport and impede the ion aggravation, thus elevating the stability of Zn anodes. The Zn2+ transference number of ERE reaches a high value of 0.822, contributing to much improved cycling life and Coulombic efficiency of plating/stripping processes of Zn anodes. Moreover, the high-entropy identity results in better anti-freezing ability of the electrolyte system, therefore ensuring the ERE stably operating even under a low temperature of −40 °C. This work can provide valuable directions for designing high-performance electrolytes for various batteries by modulating specific excess entropy.