H+/Mg2+ dual ions insertion mechanism in vanadium oxide nanosheet anode for aqueous magnesium-ion batteries

Abstract

Aqueous magnesium-ion batteries (AMIB) are attracting rising interest owing to high safety, low cost and high energy density in energy storage. Yet, it is difficult in finding high-performance anode materials, which thus hinders realization of its advantages. Herein, an ultra-thin VOx nanosheet with abundant lattice defects and large interlayer distance was obtained via an electrodeposition method, which exhibits excellent electrochemical performance as a binder-free anode for Mg2+ storage, such as a high specific capacity of 402 mAh g−1 at the current density of 0.13 Ag−1 and excellent cycling stability with 89.5 % capacity retention after 500 cycles at 4 A g−1 in 4.5 M MgCl2 aqueous electrolyte. Spectroscopy analysis indicates that VOx experiences a dual ions (H+, Mg2+) co-intercalation reaction with part of phase transition for charge storage during the discharge process. This work not only provides a charge storage mechanism of VOx in an AMIB system but also highlights a high-performance electrode material for AMIBs.