Zn2+ storage performance and structural change of orthorhombic V2O5 nanowires as the cathode material for rechargeable aqueous zinc-ion batteries

A fundamental understanding of the relationship between electrochemical performance and microstructural variation of electrodes is crucial for developing high-performance electrode materials. In this work, the Zn²⁺ storage performance and structural evaluation of orthorhombic V₂O₅ nanowires as a cathode material for Zn-ion batteries in ZnSO₄ electrolyte were investigated. At 1000 mA g⁻¹, the orthorhombic V₂O₅ nanowires exhibited a maximum reversible capacity of 276 mA h g⁻¹ and retained a capacity of 152/95 mA h g⁻¹ after 500/2000 cycles. The cycling performance curve shows three distinct regions: initial capacity increase region (stage I), fast capacity decay region (stage II), and relatively stable capacity region (stage III). The structural evolution of the orthorhombic V₂O₅ nanowires during cycling was analyzed by ex-situ SEM and XRD characterizations. It demonstrated that upon repeated cycling the orthorhombic V₂O₅ nanowires experience morphology changes from nanowires to nanofibers and finally interweaved nanofibers; meanwhile, the phase structure transforms from orthorhombic to amorphous phase and accompanied with the formation of Zn₃(OH)₂V₂O₇• 2H₂O phase, which accounts for the capacity change of the electrode during long-term cycling. The pseudocapacitive behavior and Zn²⁺ diffusion coefficient during discharge/charge processes were analyzed by the sweep voltammetry method and galvanostatic intermittent titration technique, respectively.