Boosting the cycling stability of hydrated vanadium pentoxide by Y3+ pillaring for sodium-ion batteries

Hydrated V2O5 has attracted considerable attention for sodium ion batteries (SIBs) due to its high theoretical capacity. However, the poor cycling performance caused by structural instability during sodiaton/desodiation greatly hampers its application. Herein, Y3+ pre-intercalated hydrated V2O5 samples (YxV2O5, x = 0.0, 0.02 and 0.06) are synthesized by a facile sol-gel and freeze-drying routes followed by heat treatment in air at 200 degrees C. It is found that the morphology, oxidation state of vanadium, and sodium storage performance of hydrated V2O5 could be largely modulated by Y3+ pre-intercalation. As cathode material for SIBs, the Y0.02V2O5 sample exhibits much enhanced cycling stability, higher Na+ diffusion coefficient, lower electrochemical reaction resistance, and improved rate capability compared to the pure V2O5 counterpart. First-principle calculations reveals that the pre-intercalated Y3+ forms [YO6] pillar with two oxygen atoms from the VO5 pyramids and four oxygen atoms from the intercalated water molecules, which firmly binds the V2O5 double layers together. Ex-situ XRD, SEM, and TEM analysis demonstrate that Y3+ pre-intercalation effectively strengthens the structural integrity, stabilizes the layered structure, and suppress the irreversible phase transition of hydrated V2O5 during repeated discharge/charge cycling, and therefore leading to enhanced cycling stability and improved rate capability. (C) 2018 Elsevier Ltd. All rights reserved.