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.
Keywords: CuNb13O33; anode; electrochemical property; in-situ XRD; unit-cell-volume change.