Bamboo‐Jointed Bismuth Vanadate Structural Engineering and In Situ Atomic‐Scale Insights into Anisotropy and Sodium Ion Storage

ABSTRACT In grid‐scale energy storage applications, sodium‐ion batteries have gained considerable attention due to the abundance of sodium resources, lower cost, and stable wide‐temperature performance. Monoclinic bismuth vanadate, composed of Bi─O octahedra and V─O tetrahedra interconnected by shared vertices to form a layered structure, facilitates the reversible insertion and extraction of sodium ions. However, owing to the lack of direct atomic‐level observation, the precise sodium storage mechanism remains unclear. Here, we utilized electrospinning to fabricate bamboo‐jointed BiVO 4 nanorods, whose segmented features effectively mitigate axial stress transfer, relieve volumetric strain, and suppress pulverization. Furthermore, we employ in situ transmission electron microscopy (TEM), combined with density functional theory (DFT) calculations, to investigate the structural evolution of bamboo‐jointed BiVO 4 during (de)sodiation. The anisotropic expansion of bamboo‐jointed BiVO 4 during initial sodium insertion is revealed for the first time, whereas its morphology becomes more isotropic in subsequent cycles. This transformation is attributed to the low stability of the alloyed Na‐Bi product, which promotes particle fusion. Additionally, the detailed electrochemical performance and cycling mechanism are also comprehensively elucidated. This work not only bridges the gap in understanding the sodium storage mechanism of BiVO 4 but also offers valuable insights for designing tailored morphologies for high‐performance sodium‐ion storage.