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

Hydrated V 2 O 5 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, Y 3+ pre-intercalated hydrated V 2 O 5 samples (Y x V 2 O 5 , 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 °C. It is found that the morphology, oxidation state of vanadium, and sodium storage performance of hydrated V 2 O 5 could be largely modulated by Y 3+ pre-intercalation. As cathode material for SIBs, the Y 0·02 V 2 O 5 sample exhibits much enhanced cycling stability, higher Na + diffusion coefficient , lower electrochemical reaction resistance, and improved rate capability compared to the pure V 2 O 5 counterpart. First-principle calculations reveals that the pre-intercalated Y 3+ forms [YO 6 ] pillar with two oxygen atoms from the VO 5 pyramids and four oxygen atoms from the intercalated water molecules, which firmly binds the V 2 O 5 double layers together. Ex-situ XRD , SEM, and TEM analysis demonstrate that Y 3+ pre-intercalation effectively strengthens the structural integrity, stabilizes the layered structure, and suppress the irreversible phase transition of hydrated V 2 O 5 during repeated discharge/charge cycling, and therefore leading to enhanced cycling stability and improved rate capability.