In-situ amorphous transformation of V2O5 in V2O5/V6O13 for aqueous zinc ion batteries with high capacity and long cycles

Abstract

Rechargeable aqueous zinc-ion batteries (AZIBs) are attractive due to their superior safety, rich zinc resources, and cost-efficient. Vanadium-based oxides, as popular cathode materials, are inevitably subject to dissolution in aqueous solutions, and inherent low electrical conductivity and sluggish reaction kinetics, significantly impeding the performances in Zn²⁺ storage. In this study, V₂O₅/V₆O₁₃ composites are successfully prepared by a novel three-roll milling technique combined with high-temperature treatment to improve these shortcomings. The results demonstrate that the V₂O₅/V₆O₁₃ electrode sustains excellent cycling (316.0 mAh g⁻¹ at 5 A g⁻¹ after 4000 cycles) and superior rate performance (186.69 mAh g⁻¹ at 20 A g⁻¹). Ex-situ characterization reveals that the mechanism involves the co-intercalation of H₂O with Zn²⁺. It is found by testing in different electrolytes that V₂O₅ is gradually amorphous in aqueous electrolyte during cycling, which greatly improves the structural stability and enhances the ability for capturing Zn²⁺. Moreover, it is demonstrated by calculations that a higher degree of amorphization promotes the adsorption of Zn²⁺. The present work provides a new idea for the development and mechanism explanation of high-performance AZIB materials.