Structure, Stoichiometry, and Electrochemical Performance of Li CoTi O as an Anode Material for Lithium-Ion Batteries.

Li CoTi O 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 Li CoTi O structure. The refined site-occupation result gave a nonstoichiometric chemical formula of Li CoTi O , which corresponds to a theoretical specific capacity of 322 mA h g , which is much higher than that of the stoichiometric material (233 mA h g ). The synthesized Li CoTi O material exhibits high reversible capacity (ca. 320 mA h g ), and excellent cycling stability and rate capability. A specific capacity of about 240 and 160 mA h g can be achieved at 2 and 6 A g , respectively, by the Li CoTi O material. First-principles calculation demonstrates that Ti-site deficiency decreases the bandgap and thus facilitates the electron conduction.