Sn stabilized pyrovanadate structure rearrangement for zinc ion battery

Abstract Rechargeable zinc-ion batteries (ZIBs) have shown great potential for grids-level energy storage system. However, the lack of desirable and stable cathode materials remains challenging. Herein, Sn1.5V2O7(OH)2•3.3H2O, in which pyrovanadate V2O74− group pillared with Sn oxide layer, is developed as an advanced cathode for ZIBs and a hidden reaction mechanism in SnVO cathode through in-situ Raman and ex-situ XANEs, involves the opening of V˭O edge bonding and formation of Sn–O–V bonding, which leads to charge screening effect and facilitates the fast diffusion kinetics for zinc ions, as quantitatively verified by kinetic analysis. Additionally, the tetravalent Sn ions bring about stronger ionic bonds, binding to pyrovanadate V2O74− group and leading to good stability in the pyrovanadate framework, which guarantee the cycling stability. As a result, the as-prepared SnVO shows long cycling life as well as excellent rate capability. We demonstrate that, even cycled at high current of 10 A/g, the SnVO cathode can still retain a capacity of 130 mAh/g for over 500 cycles, indicating remarkable high capacity at high rate. Our findings reveal that the tetravalent tin ions have a strong beneficial effect on the battery performance of the layered-structure cathode materials. It is believed that our study would boost further studies in other multi-valent rechargeable batteries.