Hydrated vanadium pentoxide with superior sodium storage capacity

Abstract

Sodium ion batteries (SIBs), as potential candidates for large-scale energy storage systems, have attracted great attention from researchers. Herein, a V₂O₅·nH₂O xerogel composed of thin acicular interconnected nanowire networks has been synthesized via a facile freeze-drying process. The interlayer spacing of V₂O₅·nH₂O is larger than that of orthorhombic V₂O₅ due to the intercalation of water molecules into the layer structure. As the cathode of a SIB, V₂O₅·nH₂O exhibits a high initial capacity of 338 mA h g⁻¹ at 0.05 A g⁻¹ and a high-rate capacity of 96 mA h g⁻¹ at 1.0 A g⁻¹. On the basis of combining ex-situ XRD and FTIR spectroscopy, the Na⁺ ion intercalation storage reactions are discussed in detail. By modeling calculations, the pseudocapacitive behavior makes a great contribution to the high capacities. Our work demonstrates that V₂O₅·nH₂O with large interlayer spacing is a promising candidate for high capacity sodium-based energy storage.