Inhibiting cathode dissolution and shuttling of V–O species using a polybenzimidazole hydrogel electrolyte for durable high-areal-capacity Zn–V2O5 batteries

Abstract

Aqueous Zn–V₂O₅ batteries, renowned for their intrinsic safety and high energy density, show significant promise for large-scale energy storage. Despite achieving an impressive fast-charging performance, maintaining long-term cycling performance in practical Zn–V₂O₅ batteries with high areal capacities (>2 mA h cm⁻²) at moderate cycling rates (<1C) remains a formidable challenge due to aggravated cathode dissolution issues. Herein, a polybenzimidazole (PBI) hydrogel electrolyte is developed to suppress cathode dissolution and shuttling of dissolved V–O species simultaneously. Based on advanced characterization techniques including in situ X-ray diffraction and electrochemical quartz crystal microbalance, the degradation mechanism of commercial V₂O₅ cathodes is elucidated to be both chemical dissolution, triggered by active water attack, and electrochemical dissolution, induced by pH fluctuation following proton intercalation. Accordingly, the unique electron cloud density distributions of PBI chains not only reduce the amount of free water by forming abundant hydrogen bonds but also minimize proton co-intercalation by transporting Zn²⁺ selectively. Moreover, the PBI electrolyte also effectively prevents the crosstalk of polyvanadate ions through a synergistic physical barrier and chemical adsorption effects. Therefore, the Zn–V₂O₅ battery using PBI electrolyte demonstrates one of the best low-rate cycling stabilities reported to date (∼2 mA h cm⁻² at 0.3C over 300 cycles), verifying its feasibility.