Size-Controlled Synthesis of the V₂O₅ Hollow Microspheres and Their Size-Dependent Lithium Storage Performance

Porous hollow microspheres have been recognized as attractive architectures for energy storage applications due to their high tap density, structural stability, and shortened ion diffusion pathways. However, size control of V₂O₅ hollow microspheres remains challenging, hindering the elucidation of the structure-size-property relationship and the optimization of their electrochemical properties. Herein, we report a facile route to prepare V₂O₅ hollow microspheres with tunable diameters (0.5, 2.0, and 5.0 μm) through the calcination of precursor microspheres obtained via a solvothermal method. The composition of the ethylene glycol (EG) and isopropanol (IPA) solvent mixture serves as the key parameter governing the final microsphere size. Among the synthesized samples, the 2.0-μm hollow microspheres possess the highest specific surface area (17.9 m² g^-1). When evaluated as cathode materials for lithium-ion batteries, the 2.0-μm hollow microspheres demonstrate superior electrochemical performance compared to their 0.5- and 5.0-μm counterparts. They deliver high discharge capacities of ∼220 and 95 mA h g^-1 at 0.2 and 5 C, respectively, and maintain a capacity of 135 mA h g^-1 with about 77% capacity retention after 100 cycles at 1 C. This enhanced performance is primarily attributed to the synergistic effects of their proper diameter, robust porous structure, and high surface area, which collectively facilitate efficient electrolyte infiltration, enhance charge transfer kinetics, and effectively buffer volume variations during cycling.