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

Abstract 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.