Effects of Phase Change and Cu Doping on the Li Storage Properties of Rutile TiO2

Abstract

The crystal structure and Li storage properties of Cu-doped rutile TiO2 after a phase change caused by lithiation were investigated for the first time. Structural analysis results confirmed that undoped rutile TiO2 was transformed to a distorted layered rock-salt LixTiO2 structure with a small volume expansion of only 1 % when cycled in a potential range of 1.0-3.0 V vs. Li+/Li. A substitutional solid solution of Cu2+ was formed in layered LixTiO2. The Cu doping increased both the interlayer distance and electronic conductivity of the layered LixTiO2. As an Li-ion battery anode, a Cu-doped TiO2 electrode exhibited a long cycle life, maintaining a reversible capacity of 120 mAh g−1 over 10000 cycles at 5C and an excellent rate capability of 108 mAh g−1 at 50C. Furthermore, this electrode could also be potentially used as a Na storage material. These attractive properties demonstrate high applicability of Cu-doped rutile TiO2 as a novel anode material.