Characterization of mixed titanium-niobium oxide Ti2Nb10O29 annealed in vacuum as anode material for lithium-ion battery

In this paper, the properties of mixed titanium-niobium oxide Ti2Nb10O29 (TNO) annealed in air and vacuum as anode material for lithium-ion battery were investigated. The color of TNO annealed in vacuum (V-TNO) is dark blue while white for TNO annealed in air (A-NO). Moreover, lattice parameters for V-TNO were confirmed to be slightly larger than those for A-TNO. Introduction of oxygen defect in V-TNO was confirmed by thermogravimetric analysis. X-ray photoelectron spectroscopy analysis also indicated that Ti4+ in V-TNO are partially reduced into Ti3+, due to the introduction of oxygen defect in V-TNO. Electronic conductivity at room temperature for uni-axially pressed V-NO powder is estimated to be around 10(-6)-10(-5) S cm(-1), which is more than three digits higher than that for pressed A-NO powder (= 10(-9) S cm(-1)). The enhancement of intrinsic electronic conductivity of TNO greatly contributes for improving the rate performance. At low current density of 0.5 mA cm(-2), both A-TNO and V-NO showed reversible capacity around 250 mAh g(-1) at potential range from 1.0 to 2.5 V vs. Li/Li+, while at higher current density of 10 mA cm(-2), V-NO maintained much higher discharge capacity of 150 mAh g(-1) than that for TNO (= 50 mAh g(-1)). (C) 2014 Elsevier B.V. All rights reserved.