Preparation and electrochemical properties of Ca-doped Li4Ti5O12 as anode materials in lithium-ion battery

Ca-doped lithium titanates with the formula of Li4-xCaxTi5O12 (x= 0, 0.05, 0.1, 0.15, 0.2) were synthesized as anode materials by a simple solid-state reaction in an air atmosphere. The phase structure, morphologies and electrochemical properties of the prepared powders were systematically characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and cyclic voltammetry (CV), respectively. XRD revealed that the Ca-doping caused no change on the phase structure and highly crystalline Li4-xCaxTi5O12 (0 <= x <= 0.2) powders without any impurity were obtained. SEM images sfiowed that all samples had similar particulate morphologies and the particle size distribution was in the range of 1-2 mu m. It was observed that Ca-doped lithium titanates employed as the anode materials of lithium-ion batteries delivered excellent electrochemical performances, and sample Li3.9Ca0.1Ti5O12 exhibited a higher specific capacity, better cycling performance and rate capability than other samples. The Li3.9Ca0.1Ti5O12 material showed discharge capacities of 162.4 mAh g(-1), 148.8 mAh g(-1) and 138.7 mAh g(-1) after 100 cycles at 1 C, 5C and 10 C charge-discharge rates, respectively. Electrochemical impedance spectroscopy (EIS) revealed that the Li3.9Ca0.1Ti5O12 electrode exhibited the highest electronic conductivity and fastest lithium-ion diffusivity, which indicated that this novel Li3.9Ca0.1Ti5O12 material was promising as a high-rate anode material for the lithium-ion batteries. (C) 2013 Elsevier Ltd. All rights reserved.