Controlled Heterovalent Vanadium Ion Coordinated Flower-Shaped Supramolecules Cathode for Zinc-Ion Storage.

Vanadium-based materials, which offer multiple oxidation states and rich redox reactions in zinc-ion batteries (ZIBs), have gained substantial attention. However, achieving green and efficient preparation of vanadium oxides-based materials featured with a controlled content of different heterovalent vanadium remains a significant challenge. Herein, a vanadium-supramolecular flower-shaped material (VSF) with heterovalent vanadium was prepared using NHVO as vanadium metal center and hexamethylenetetramine as organic ligand in aqueous solution. The optimal ratio of material (PVSF) after controlling VSF presintering is 2/1 (V/V). Employing PVSF-2/1 as cathode in ZIBs can achieve a high specific capacity of 398.9 mAh g at 0.2 A g, which is increased by 0.2 and 3.5 times as compared with that of pure VO and VO, respectively. After 2000 cycles, it still delivers a specific capacity of 225 mAh g at 5.0 A g. The Zn∥PVSF-2/1 pouch cells were assembled with a satisfactory specific capacity of 339 mAh g at a current of 0.2 A g. The excellent performance is ascribed to regulation and coordinated promotion of heterovalent states. The structural pathways corresponding to V act as Zn transport channels to increase Zn transport capability. The V cause high charge density distribution of the V-O lattice layer to provide abundant active sites for the adsorption/desorption process of Zn.