Structure, Stoichiometry, and Electrochemical Performance of Li2CoTi3O8 as an Anode Material for Lithium-Ion Batteries

Li2CoTi3O8 powder has been synthesized by a simple citric nitrate method and was evaluated as an anode material for lithium-ion batteries. The X-ray diffraction (XRD) Rietveld refinement and X-ray photoelectron spectroscopy (XPS) measurements indicate the existence of Ti-site deficiency and a mixed-valence state of Co ions in the Li2CoTi3O8 structure. The refined site-occupation result gave a nonstoichiometric chemical formula of Li2CoTi2.682O8, which corresponds to a theoretical specific capacity of 322mAhg(-1), which is much higher than that of the stoichiometric material (233mAhg(-1)). The synthesized Li2CoTi2.682O8 material exhibits high reversible capacity (ca. 320mAhg(-1)), and excellent cycling stability and rate capability. A specific capacity of about 240 and 160mAhg(-1) can be achieved at 2 and 6Ag(-1), respectively, by the Li2CoTi2.682O8 material. First-principles calculation demonstrates that Ti-site deficiency decreases the bandgap and thus facilitates the electron conduction.