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.