Ultrafast rate capability of V₂O₅ yolk-shell microspheres with hierarchical nanostructure as an aqueous lithium-ion battery anode

Aqueous rechargeable lithium-ion batteries (ARLBs) are promising candidates in grid-scale energy storage systems due to their high safety and low cost. However, it remains a major challenge to develop advanced anode materials with favorable specific capacity and long cycle life. Herein, we fabricate V₂O₅ yolk-shell microspheres with hierarchical nanostructure as anode material of ARLBs. Annealing temperature-dependent experiments are carried out to investigate the evolution of crystallinity, morphology and structure of the samples. As the annealing temperature varies from 300 °C to 350 °C to 400 °C, the building blocks of microspheres gradually change from nanoplates to nanoclusters to larger nanoparticles. The electrochemical performances of different samples are compared and analyzed. In half-cell tests, the sample annealed at 350 °C (VO-350) achieves a high capacity of 258.6 mA h g ⁻¹ at 0.5 A g ⁻¹ and ultrafast rate capabilities such as 149.7 mA h g ⁻¹ at 15 A g ⁻¹. In full-cell tests, the VO-350//LiMn₂O₄ coin cells exhibit favorable cycle life with a capacity retention of 71.5% after 500 cycles at 1 A g ⁻¹ and ultrafast rate capabilities such as 87.4 mA h g ⁻¹ at 15 A g ⁻¹. In addition, the electrochemical kinetics and energy storage mechanism of V₂O₅ in ARLBs are investigated.