Insight into the Critical Role of Oxygen Vacancies and V=O Bonds Length in V 2 O 5 for Advanced Zinc Ion Storage.

Due to the larger sizes and stronger positive polarity of Zn 2+ than dominant univalent ions, Zn 2+ sluggish diffusion within V 2 O 5 host electrodes is an essential issue in developing aqueous zinc-ion batteries (ZIBs) of higher energy densities. Herein, a high-performance V 2 O 5 cathode was developed through subtly synthesizing and tuning V 2 O 5 with oxygen vacancies-enriched and elongated apical V=O 1 bond by altering the gradient concentration of hydrazine hydrate in the gas-solid reaction system. This strategy can enhance both intrinsic and extrinsic conductivity to a large extent. The electrochemical testing demonstrated the oxygen vacancies-enriched and elongated apical V=O 1 bond can not only increase the intrinsic electronic conductivity of V 2 O 5 , but also induce additional pseudocapacitance to enhance the Zn 2+ diffusion kinetics. We used infrared spectroscopy and Raman spectroscopy to characterize the change in the bond length structure of V 2 O 5 . Simultaneously, the long-term cyclability (capacity retention of 76.9 % after 1200 cycles at 4.0 A g -1 ) and rate capabilities (218 mAh g -1 at 4.0 A g -1 ) are promoted as well. We believe that our work might shed light on the bond length engineering of V 2 O 5 and provide insights for the reasonable designing of novel cathodes for practical rechargeable ZIBs.