Author: Yinshi Li (Xi’an Jiaotong University) - Alkaline zinc-based flow batteries (AZFBs) are considered highly promising candidates for large-scale energy storage systems due to their advantages of abundant resources, high open-circuit voltage, and high energy density. Nevertheless, the cycle life of these batteries is significantly shortened by the growth of dendritic zinc dendrites, which stems from the contradiction between sluggish Zn2+ transport in the electrolyte and rapid electrochemical reaction kinetics at the electrode interface. Here, we propose an electrolyte solvation structure regulation strategy employing L-asparagine (C4H8N2O3, Asn) to balance ion transport and reduction kinetics, thereby achieving uniform and dense zinc deposition and enhancing the cycle life of AZFBs. Intriguingly, Asn can coordinate with Zn2+ to form a novel solvation structure with lower electrostatic potential. This effectively shields the coulombic repulsion between Zn2+ and enhances the Zn2+ transport rate in the bulk electrolyte. Meanwhile, the new coordination structure exhibits reduced solvation energy, which increases the charge transfer barrier and moderates the electrochemical reduction kinetics. Additionally, the introduction of Asn reshapes the hydrogen bond network, effectively suppressing Fe2+/Fe3+ crossover during long-term charge-discharge processes. Notably, experimental results demonstrate that at a current density of 50 mA cm-2 and an areal capacity of 30 mAh cm-2, the cycle life of Asn-modified AZFBs increased from 66.14 h to 208.02 h compared to batteries using the pristine electrolyte. Furthermore, the Asn-modified AZFBs maintained a coulombic efficiency of 98.78% and an energy efficiency of 80.17% even after 180 cycles. This work elucidates a novel strategy for effectively suppressing zinc dendrites through scientific regulation of electrolyte solvation structures, providing new research perspectives for developing high-stability, long-life alkaline zinc-based flow batteries.
