Enhanced Lithium Storage in Micrometer‐Scale Tungsten Bronze Mo ₃ Nb ₂ O ₁₄ by Molybdenum Reduction and Oxygen Deficiency

Abstract Tungsten bronze transitional metal oxides are potential candidate anode material for lithium‐ion batteries (LIBs) owing to their open multichannel frame structure facilitating lithium transport and storage. Herein, the molybdenum reduction and oxygen deficiency are enhanced in micrometer‐scale Mo ₅ O ₁₄ ‐type tungsten bronze structure Mo ₃ Nb ₂ O _{14− x} (V‐MNO) that is prepared by a solid‐state reaction in vacuum. Neutron powder diffraction data indicate that oxygen vacancies are located at both three‐coordinated ( µ ³ ) oxygen sites around filled pentagonal rings and normally two‐coordinated ( µ ² ) oxygen sites. As anode material for LIBs, benefiting from the increased Mo reduction, facilitating the electronic transport and oxygen vacancies without strong site preferences, widening the intratunnel, and opening up the intertunnel migration paths for lithium ions, V‐MNO displays enhanced electrochemical properties with an initial discharge capacity of ≈322 mAh g ⁻¹ , a charge capacity of ≈274 mAh g ⁻¹ , and a reversible capacity of ≈147.2 mAh g ⁻¹ (at 400 mA g ⁻¹ ) after 200 cycles. The LiCoO ₂ //V‐MNO full cell shows a discharge capacity of 145.4 mAh g ⁻¹ after 100 cycles at 100 mA g ⁻¹ . These results underline significance of controlling defect chemistry on the cationic reduction and oxygen vacancies in micrometer‐scale tungsten bronze transition metal oxides as an effective strategy for enhancing their storage performance as anode materials.