Carbon-Coated CuNb₁₃O₃₃ as A New Anode Material for Lithium Storage

Niobates are very promising anode materials for Li⁺-storage rooted in their good safety and high capacities. However, the exploration of niobate anode materials is still insufficient. In this work, we explore ~1 wt% carbon-coated CuNb₁₃O₃₃ microparticles (C-CuNb₁₃O₃₃) with a stable shear ReO₃ structure as a new anode material to store Li⁺. C-CuNb₁₃O₃₃ delivers a safe operation potential (~1.54 V), high reversible capacity of 244 mAh g^-1, and high initial-cycle Coulombic efficiency of 90.4% at 0.1C. Its fast Li⁺ transport is systematically confirmed through galvanostatic intermittent titration technique and cyclic voltammetry, which reveal an ultra-high average Li⁺ diffusion coefficient (~5 × 10^-11 cm² s^-1), significantly contributing to its excellent rate capability with capacity retention of 69.4%/59.9% at 10C/20C relative to 0.5C. An in-situ XRD test is performed to analyze crystal-structural evolutions of C-CuNb₁₃O₃₃ during lithiation/delithiation, demonstrating its intercalation-type Li⁺-storage mechanism with small unit-cell-volume variations, which results in its capacity retention of 86.2%/92.3% at 10C/20C after 3000 cycles. These comprehensively good electrochemical properties indicate that C-CuNb₁₃O₃₃ is a practical anode material for high-performance energy-storage applications.