Enhanced charge storage of nanometric ζ-V2O5 in Mg electrolytes

Abstract

V₂O₅ is of interest as a Mg intercalation electrode material for Mg batteries, both in its thermodynamically stable layered polymorph (α-V₂O₅) and in its metastable tunnel structure (ζ-V₂O₅). However, such oxide cathodes typically display poor Mg insertion/removal kinetics, with large voltage hysteresis. Herein, we report the synthesis and evaluation of nanosized (ca. 100 nm) ζ-V₂O₅ in Mg-ion cells, which displays significantly enhanced electrochemical kinetics compared to microsized ζ-V₂O₅. This effect results in a significant boost in stable discharge capacity (130 mA h g⁻¹) compared to bulk ζ-V₂O₅ (70 mA h g⁻¹), with reduced voltage hysteresis (1.0 V compared to 1.4 V). This study reveals significant advancements in the use of ζ-V₂O₅ for Mg-based energy storage and yields a better understanding of the kinetic limiting factors for reversible magnesiation reactions into such phases.