Carbon-Coated CuNb 13 O 33 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 CuNb 13 O 33 microparticles (C-CuNb 13 O 33 ) with a stable shear ReO 3 structure as a new anode material to store Li + . C-CuNb 13 O 33 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 cm 2 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-CuNb 13 O 33 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-CuNb 13 O 33 is a practical anode material for high-performance energy-storage applications.