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

• Ca-doped Li4Ti5O12 samples were prepared by a simple solid-state method.
• The high-rate performance of Li4−xCaxTi5O12 (0 ≤ x ≤ 0.2) anode was first reported.
• Li3.9Ca0.1Ti5O12 shows the best high-rate performance.

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 showed that all samples had similar particulate morphologies and the particle size distribution was in the range of 1–2 μm. 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, 5 C 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.

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