Visualizing Synergetic Cation‐Specific Distortion of Oxygen Polyhedra in High‐Rate Mo₃Nb₂O₁₄ Anode

Abstract Niobium‐based oxides have emerged as promising anode materials for minute‐level fast‐charging lithium ion batteries. However, the atomic mechanisms of their ultrafast ionic kinetics remain an enigma due to limitations in experimental characterizations. Here, Li + accommodation behaviors and corresponding lattice distortion of high‐rate Mo 3 Nb 2 O 14 anode are directly observed at the atomic‐scale by combining scanning transmission electron microscopy and in situ X‐ray diffraction. The sequential insertion of Li + into hexagonal, pentagonal, and tetragonal tunnels is resolved directly, verifying a three‐stage reaction mechanism with anisotropic lattice evolution. Atomic elemental imaging quantifies the Mo/Nb cation ordering rather than previously supposed as disordering. Quantitative symmetry analysis of oxygen polyhedra reveals the rigidity of the Nb polyhedra but the flexibility of the Mo polyhedra, which synergistically renders a stable framework with ultrafast ionic transport. These results provide atomic insights into cation‐specific roles in niobium‐based anode materials, thus paving the way for the rational design of high‐performance electrode materials.