Boosting zinc ion storage performance of sandwich-like V2O5/graphene composite by effectively inhibiting vanadium dissolution

Improving the stability of the layered structure and suppressing vanadium dissolution during repeated Zn2+ insertion/extraction processes are considered to be the key to promote the electrochemical stability of vanadium-based cathodes for ZIBs. In this work, a group of sandwich-like V2O5/graphene composites (V2O5/xG) were controllably fabricated by tuning the amount of hydrophobic graphene. With the increase of graphene content, the corresponding electrochemical properties show a parabolic trend that increase first and then decrease. A maximum capacity of 270 mAh g-1 after 100 cycles at 0.1 A g-1 and a superior cycle stability with 82.4% capacitance retention after 6000 cycles at 10 A g-1 are achieved when the amount of graphene is about 10.4% (that is V2O5/5G). The addition of graphene has been proven not only to act as an effective conductive network to promote charge transfer and enhance the pseudocapacitance effect on the electrode surface; but also to increase the electrode hydrophobicity, effectively inhibiting the dissolution of vanadium, and promoting the desolvation and diffusion kinetics of hydrated zinc ions. Moreover, the graphene layer, as a structural stabilizer, effectively prevents the structure of the active component V2O5 from collapsing during cycling, contributing to the long-term cycle life.