Electrochemically grown nanocrystalline V2O5 as high-performance cathode for sodium-ion batteries

Nanocrystalline V2O5 with a bilayer structure is directly grown on a steel substrate electrochemically in VOSO4-based solution as a cathode for sodium-ion batteries. No complicated slurry preparation procedure, involving polymer binder and conducting agent additions, is needed for this electrode synthesis. The incorporation of NaCH3COO in the VOSO4 solution promotes oxide growth and improves oxide film uniformity. The interlayer distance between two-dimensional V2O5 stacks in the structure is as large as ∼11.6 Å, which is favorable for accommodating Na+ ions. The growth potential is critical to determine the oxide architectures and thus the corresponding Na+ storage properties (in terms of capacity, high-rate capability, and cycling stability). An optimal charge-discharge capacity of 220 mAh g−1 is achieved for V2O5 grown in an activation-controlled potential region (i.e., 0.8 V vs. an Ag/AgCl reference electrode). This V2O5 electrode shows only 8% capacity decay after 500 cycles.