Urchin-like Spinel MgV2O4 as a Cathode Material for Aqueous Zinc-Ion Batteries

The rechargeable aqueous zinc-ion battery is a promising candidate for energy storage demands owing to its low cost, intrinsic safety, and ecofriendliness. However, existing aqueous zinc-ion batteries are far from achieving the exploration of appreciable cathode materials because multivalent ions have the strong charge repulsion with the host material and inherent sluggish kinetics during the charge and discharge process. Herein, we introduce a novel urchin-like magnesium vanadate as the cathode material for aqueous zinc-ion batteries. Specifically, the battery delivers a high capacity of 272 mA h g–1 at 0.2 A g–1 and an excellent long-term cycling stability with a reversible capacity of 128.9 mA h g–1 even after 500 cycles at 4.0 A g–1. Additionally, the calculated energy density for the MgV2O4 cathode is 171.5 W h kg–1 at 140.6 W kg–1 power density. These remarkable electrochemical performances are attributed to the crystal structure of urchin-like MgV2O4 with low-valence vanadium, transforming from the order to disorder and producing a new phase during the electrochemical cycling process. This work may open an avenue for the application of low-valent vanadium-based materials for aqueous zinc-ion storage.