Exploring the Disparities\nin Capacity and Cycling\nStability of NH<sub>4</sub>V<sub>4</sub>O<sub>10</sub> Cathodes in\nZnSO<sub>4</sub> and Zn(OTf)<sub>2</sub> Electrolytes

This\ninvestigation delves into the critical role of electrolyte\nselection in determining the capacity and cycling stability of NH<sub>4</sub>V<sub>4</sub>O<sub>10</sub> (NVO) cathodes within aqueous\nzinc-ion batteries. As a commonly used electrolyte, ZnSO<sub>4</sub> electrolyte, while economical, exhibits suboptimal performance due\nto earlier byproduct formation and the presence of less soluble byproducts\ncompared to Zn(OTf)<sub>2</sub> electrolyte. This leads to slower\nelectrochemical kinetics, increased impedance, and ultimately, lower\ncapacity. Furthermore, the original NVO cathode undergoes partial\ntransformation into a lower capacity cathode of Zn<sub>3</sub>(OH)<sub>2</sub>V<sub>2</sub>O<sub>7</sub>·2H<sub>2</sub>O (ZVO) after\nmultiple cycles in ZnSO<sub>4</sub> electrolyte, contributing to further\ndegradation in cycling stability. In stark contrast, the use of Zn(OTf)<sub>2</sub> electrolyte demonstrates superior cyclability, characterized\nby the absence of ZVO formation and the reversible generation/disappearance\nof byproduct ZBS, thereby delivering enhanced cycling stability. These\nobservations are corroborated by kinetic analyses employing electrochemical\nimpedance spectroscopy (EIS), galvanostatic intermittent titration\ntechnique (GITT), and in situ pH measurements. This study provides\nvaluable insights into the intricate interplay between electrolyte\nchoice, byproduct formation, and battery performance, offering valuable\nguidance for optimizing electrolyte selection in aqueous zinc-ion\nbatteries.