Rational Design of V₂O₅ Hierarchical Microspheres with Tunable Porosities and Primary Building Blocks for Enhanced...

The lithium storage performance of vanadium pentoxide (V₂O₅) cathodes is intrinsically linked to their hierarchical architecture, yet achieving precise control over the morphology, porosity, and primary building block size remains a significant challenge. Herein, we report a systematic investigation into the controllable synthesis of V₂O₅ hierarchical structures by selecting the vanadium precursor and solvent system in a solvothermal process followed by calcination. Using ammonium metavanadate (NH₄VO₃) in an ethylene glycol/nitric acid (EG/HNO₃) mixed solvent yields uniform hierarchical porous microspheres (V₂O₅-HPM) assembled from primary nanoparticles (40-60 nm) and possessing a large specific surface area of 17.3 m² g^-1. Replacing the vanadium precursor with vanadyl acetylacetonate [VO(C₅H₇O₂)₂] under otherwise identical conditions fabricates porous microspheroids (V₂O₅-PMS) with a lower surface area (11.1 m² g^-1). Substituting EG with isopropanol (IPA) while retaining NH₄VO₃ results in flower-like porous microspheroids (V₂O₅-FPM) assembled from coarse plates (>100 nm) with a reduced surface area (5.8 m² g^-1). Electrochemical evaluation reveals that V₂O₅-HPM exhibits superior lithium storage performance, delivering a reversible capacity as high as 240 mAh g^-1 at 0.2C, a remarkable rate performance of 105 mAh g^-1 at 5C, and a capacity retention of 82% after 100 cycles at 1C. These benefits arise from the synergistic architectural features of V₂O₅-HPM. Its high surface area and mesoporous network facilitate rapid electrolyte infiltration and Li⁺ transport, while the robust assembly of uniform nanoparticles effectively buffers volume changes during cycling. This work establishes a rational strategy for tailoring V₂O₅ hierarchical structures and provides valuable insights into the structure-property relationships governing high-performance cathode materials.