Microwave-Hydrothermal Synthesis of Hierarchical Sb₂WO₆ Nanostructures as a New Anode Material for Sodium Storage

Novel hierarchical antimony tungstate (Sb₂WO₆) nanostructures with hollow disk-like morphology, which are layer-by-layer assembled from Sb₂WO₆ nanosheets, are prepared by a facile microwave-hydrothermal method. The as-prepared Sb₂WO₆ is firstly applied as an anode material for sodium ion batteries (SIBs), which shows superior cycle stability and rate capability, delivering a reversible capacity of ∼350 mA h/g after 100 cycles at 200 mA/g and even ∼285 mA h/g at a high rate of 2 A/g. The sodium storage mechanism is revealed via ex-situ transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) analyses, which is based on the reversible alloying/dealloying reaction (Sb + 3 Na⁺ + 3e-↔ Na³Sb) and the reversible conversion reaction (Na₂WO₄ + 6 Na⁺ + 6e⁺ ↔ W + 4 Na₂O) in the ternary oxide of Sb₂WO₆. The different sodiation/desodiation reactions in the Sb₂WO₆ electrode happens in a step-wise manner owing to the different working potentials, which thus alleviate the volume change induced pulverization and synergistically contribute to the superior sodium storage performance.