Cr0.5Nb24.5O62 Nanowires with High Electronic Conductivity for High-Rate and Long-Life Lithium-Ion Storage.

Abstract

Intercalation-type TiNbxO2+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 TiNbxO2+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 Cr0.5Nb24.5O62 nanowires as an intercalation-type anode material for high-performance LIBs. The as-made Cr0.5Nb24.5O62 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.