Highly conductive CrNb11O29 nanorods for use in high-energy, safe, fast-charging and stable lithium-ion batteries

Ti2Nb2xO4+5x compounds are very popular negative-electrode materials for lithium-ion batteries due to their high specific capacities, safe operating potentials and high cycling stability. Nevertheless, their poor electronic conductivities and insufficient Li+ diffusion coefficients limit the rate capabilities. Herein, we explore highly conductive CrNb11O29 with a high theoretical capacity (401 mAh g(-1)) and an open Wadsley-Roth shear structure as a new intercalating negative-electrode material having the same advantages of Ti2Nb2xO4+5x but a high rate capability. CrNb11O29 nanorods (CrNb11O29-R) with lengths of 500-1000 nm and very small diameters of 30-50 nm are prepared based on a novel hydrothermal method. Due to the free electrons in Cr-3d orbitals and the large ionic radius of Cr3+, CrNb11O29 exhibits a high electronic conductivity and large Li+ diffusion coefficients, respectively. In-situ X-ray diffraction analyses confirm its high structural stability. These conductivity, structural and architectural advantages in CrNb11O29-R lead to its significant pseudocapacitive contribution (82.0% at 1.1 mV s(-1)), prominent rate capability (high reversible capacities of 343 mAh g(-1) at 0.1C and 228 mAh g(-1) at 10C), and outstanding cycling stability (only 8.9% capacity loss at 10C over 400 cycles).