Cr_0.5Nb_24.5O₆₂ Nanowires with High Electronic Conductivity for High-Rate and Long-Life Lithium-Ion Storage

Abstract

Intercalation-type TiNb_xO_2+2.5x (x = 2, 5, and 24) anode materials have recently become more interesting for lithium-ion batteries (LIBs) due to their large theoretical capacities of 388-402 mAh g^-1. However, the Ti⁴⁺/Nb⁵⁺ ions in TiNb_xO_2+2.5x with empty 3d/4d orbitals usually lead to extremely low electronic conductivity of <10^-9 S cm^-1, greatly restricting their practical capacity and rate capability. Herein, we report a class of highly conductive Cr_0.5Nb_24.5O₆₂ nanowires as an intercalation-type anode material for high-performance LIBs. The as-made Cr_0.5Nb_24.5O₆₂ nanowires show an open shear ReO₃ crystal structure (C2 space group) with 4% tetrahedra and a conducting characteristic with ultrahigh electronic conductivity of 3.6 × 10^-2 S cm^-1 and a large Li⁺-ion diffusion coefficient of 2.19 × 10^-13 cm² s^-1. These important characteristics make them deliver outstanding electrochemical properties in term of the largest reversible capacity (344 mAh g^-1 at 0.1 C) in all the known niobium- and titanium-based anode materials, safe working potential (∼1.65 V vs Li/Li⁺), high first-cycle Coulombic efficiency (90.8%), superior rate capability (209 mAh g^-1 at 30 C), and excellent cycling stability, making them among the best for LIBs in niobium- and titanium-based anode materials.