NiCo₂V₂O₈@NC Spheres with Mesoporous Yolk- Bilayer Hierarchical Structure for Enhanced Lithium Storage

Metal vanadates as negative electrode materials for lithium-ion batteries have attracted widespread attention, attributed to their substantial capacity, broad availability, and exceptional safety. In this study, NiCo₂V₂O₈@NC microspheres featuring a yolk-double shell structure were successfully synthesized via ion exchange reactions and surface deposition techniques, employing metal glycerolate as a template. Owing to the bimetallic cobalt-nickel synergistic effect and the N-doped carbon network, this configuration not only optimizes the pore structure but also enhances conductivity, thereby augmenting the stability of the overall structure. The unique yolk-double shell design significantly enhances the utilization of active components and reduces the ion transport distance, thereby achieving high capacity. Thanks to the synergistic effects of this bimetallic and intricate structure, the material demonstrates exceptional capacity and cycle stability in lithium storage. The initial discharge capacity possesses 1522 mAh g^-1 at a current density of 0.2 A g^-1, with the reversible capacity still maintained at 1197 mAh g^-1 after 100 cycles. In addition, at a high current density of 0.5 A g^-1, the initial discharge capacity is 1487 mAh g^-1, with a reversible capacity of 747 mAh g^-1 maintained after 500 cycles. This study offers a perspective and methodology for the design and fabrication of complex porous double shell nanostructures.