Inhibiting cathode dissolution and shuttling of V-O species by 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, hold significant promises for large-scale energy storage. Despite achieving impressive fast-charging performance, maintaining long-term cycling performance in practical Zn-V2O5 batteries with high areal capacities (> 2 mAh cm-2) at moderate cycling rates (< 1 C) 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 characterizations including in-situ X-ray diffraction and electrochemical quartz crystal microbalance, the degradation mechanism of commercial V2O5 cathode is elucidated to 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 synergistic physical barrier and chemical adsorption effects. Therefore, the Zn-V2O5 battery using PBI electrolyte demonstrate one of the best low-rate cycling stabilities reported to date (~ 2 mAh cm-2 at 0.3 C over 300 cycles), verifying its feasibility.