Tailored Crystal Planes of Vo2 Cathode Power Fast Zn2+ Storage

Abstract

Vanadium dioxide (VO2) cathode with specific tunnel structure and favorable specific capacity is critical for developing aqueous zinc-ion batteries (AZIBs) with excellent electrochemical performance. However, sluggish electrochemical kinetics hampered its development in burgeoning energy storage devices. Herein, we tailored VO2 material with different exposed crystal planes and employed as cathodes for AZIBs. The comprehensive analyses indicate the exposed (201) and (001) crystal planes are favorable for fast electrochemical kinetics, high capacitance storage, and the smallest diffusion energy barrier, which guarantee electrodes with high discharge capacity (367 mA h g-1 at 0.1 A g-1), excellent rate capability (281 mA h g-1 at 4 A g-1) and cycling stability over 800 cycles. Besides, Ex-situ characterizations manifest VO2 cathode with specific exposed crystal planes easily transformed to Zn3+x(OH)2V2O7∙2H2O in the first discharge process, hence allowing continuous embedding of Zn2+ in this layered structure, and the ex-situ scanning electron microscopy (SEM) analysis confirms the morphology change matched well with the structural transformation. This study may enlighten and promote the role of exposed crystal plane to develop high-performance rechargeable batteries.

Keywords: vanadium dioxide, exposed crystal plane, structural transformation, diffusion energy barrier, electrochemical kinetics