Aluminum vanadate hollow spheres as zero-strain cathode material for highly reversible and durable aqueous zinc-ion batteries

The intercalation and conversion compounds have long been exploited in aqueous zinc-ion batteries such as Prussian blue, VS2, Zn0.25V2O5, MnO2 and so on. However, the lattice distortion of host materials during Zn ions insertion is the major issue with cycling stability. Metastable-phase vanadium oxide with bilayer structure, low crystallinity and interstitial water molecules may decrease lattice distortion, leading to long cycle stability. Herein we demonstrate H11Al2V6O23.2 (HAVO) microspheres with large interlayer distance (d(001) = 1.336 nm) as cathode materials for zinc-ion batteries. The Zn ions insertion/extraction behaviors are investigated deeply. Ex-situ XRD and Raman spectra of HAVO collected at various states show no shift during battery operation, indicating the lattice distortion is nearly negligible. In addition, the lattice structure is well maintained even after 1000 cycles and the HAVO delivers an outstanding reversibility (88.6% capacity retention after 7000 cycles).