The projected low cost and inherent safety of rechargeable aqueous zinc-ion batteries make energy storage devices based on the technology seem like a real winner. Large stationary versions of such batteries could be particularly useful for grid storage applications involving intermittent power sources such as wind turbines and solar panels. But the batteries haven’t gotten off the ground yet, mainly because of unsatisfactory cathodes, which cause the devices to act sluggishly and die quickly. University of Waterloo researchers led by Linda F. Nazar have now come up with a layered vanadium oxide featuring interlayer zinc ions and water molecules that seems to bypass those problems (Nat. Energy 2016, DOI: 10.1038/nenergy.2016.119). The team used a microwave-driven hydrothermal method to synthesize ribbonlike single crystals of Zn0.25V2O5•nH2O (n = 0.85–1.0) and fashioned cathodes from thin films of the material. They paired the cathodes with metallic zinc anodes to make test cells. Analyses based on X-ray diffraction and other methods show that on discharge Zn2+ ions from the anode intercalate reversibly into the cathode, reducing the oxide and displacing water molecules. The team reports that test cells exhibit kinetic properties comparable with commercial lithium-ion battery cathodes and retain 80% of their charge capacity during 1,000 charging cycles.