Mixed-Dimensional (2D/3D/3D) Heterostructured Vanadium Oxide with Rich Oxygen Vacancies for Aqueous Zinc Ion Batteries with High Capacity and Long Cycling Life

Heterostructure engineering and oxygen vacancy engineering are the most promising modification strategies to reinforce the Zn²⁺ ion storage of vanadium oxides. Herein, a rare mixed-dimensional material (VO_x), composed of V₂O₅ (2D), V₃O₇ (3D), and V₆O₁₃ (3D) heterostructures, rich in oxygen vacancies, was synthesized via thermal decomposition of layered ammonium vanadate. The VO_x cathode provides an exceptional discharge capacity (411 mA h g^-1 at 0.1 A g^-1) and superior cycling stability (the capacity retention remains close to 100% after 800 cycles at 2 A g^-1) for aqueous zinc-ion batteries (AZIBs). Ex situ characterizations confirm that the byproduct Zn₃V₂O₇(OH)₂·nH₂O is generated/decomposed during discharge/charge processes. Furthermore, VO_x demonstrates reversible intercalation/deintercalation of H⁺/Zn²⁺ ions, enabling efficient energy storage. Remarkably, a reversible crystal-to-amorphous transformation in the V₂O₅ phase of VO_x during charge-discharge was observed. This investigation reveals that mixed-dimensional heterostructured vanadium oxide, with abundant oxygen vacancies, serves as a highly promising electrode material for AZIBs, further advancing the comprehension of the storage mechanism within vanadium-based cathode materials.