Mo₃Nb₁₄O₄₄: A New Li⁺ Container for High-Performance Electrochemical Energy Storage

Intercalating Nb-based oxides are promising anode compounds for lithium-ion batteries since they have both good safety and large capacities. However, the research in this field is still limited. Here, Mo₃Nb₁₄O₄₄ with a large theoretical capacity of 398 mAh g^–1 (Mo⁶⁺↔Mo⁴⁺ and Nb⁵⁺↔Nb³⁺) is exploited as a new Nb-based oxide anode compound, and Mo₃Nb₁₄O₄₄ micron-sized particles (Mo₃Nb₁₄O₄₄-M) and Mo₃Nb₁₄O₄₄ nanowires (Mo₃Nb₁₄O₄₄-N) are demonstrated. Mo₃Nb₁₄O₄₄ owns a tetragonal shear ReO₃ crystal structure (high-symmetric I4 space group) constructed by 4 × 4×∞ (Mo,Nb)O₆ octahedron blocks linked by MoO₄ tetrahedra, forming an A–B–A layered structure with a large interlayer spacing. This interesting structure allows fast Li⁺ storage within the interlayers and significant intercalation-pseudocapacitive behavior, leading to the high rate performance of Mo₃Nb₁₄O₄₄-M/Mo₃Nb₁₄O₄₄-N with a large 10C versus 0.1C capacity retention percentage of 38.1/54.2%. Mo₃Nb₁₄O₄₄-M/Mo₃Nb₁₄O₄₄-N further exhibits a safe operating potential of 1.72/1.68 V, large reversible capacity of 323/321 mAh g^–1 at 0.1C, high initial coulombic efficiency of 92.2/90.0%, and good cycling stability with 71.8/75.8% capacity retention after 1000 cycles at 10C. Additionally, a LiMn₂O₄/Mo₃Nb₁₄O₄₄-N full cell also performs well. Therefore, Mo₃Nb₁₄O₄₄ holds great promise as a fast-charging, safe, large-capacity, high-efficient, and long-life Li⁺ anode container.