Preparation and electrochemical properties of Mg2+ and F? co-doped Li4Ti5O12 anode material for use in the lithium-ion batteries

By Bai, Xue; Li, Wen; Wei, Aijia; Li, Xiaohui; Zhang, Lihui; Liu, Zhenfa
Published in Electrochimica Acta NULL 2016

Abstract

Abstract Spinel Li4Ti5O12 co-doped with Mg2+ and F? was synthesized by solid-state reaction of anatase TiO2, Li2CO3, NH4F, and Mg(NO3)2. For comparison, Mg2+-doped and F?-doped Li4Ti5O12 were prepared using the same method. The structure and electrochemical performance of the prepared materials were investigated by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, high-resolution transmission electron microscopy, electrochemical impedance spectroscopy, and galvanostatic charge-discharge tests. Using an internal standard and Rietveld refinement, we calculated the lattice parameters of the samples. After co-doping with Mg2+ and F?, the dopant ions enter the Li4Ti5O12 lattice, resulting in the reduction of Ti4+ to Ti3+, and increasing the conductivity of the material. Furthermore, the Mg2+ and F? co-doping technique resulted in smaller primary particles with a narrow size distribution, factors that can accelerate transfer of Li+ between the electrode and electrolyte. Consequently, the Mg2+ and F? co-doped Li4Ti5O12 material exhibits a superior rate performance and delivers discharge capacities of 159.4, 154.1, 146.5, 120.8, 102.7, and 76 mAh g?1 at 0.2C, 0.5C, 1C, 3C, 5C, and 10C, respectively, significantly higher than those of pure Li4Ti5O12 (155.4, 138.6, 124.2, 94.1, 76.7, and 52.2 mAh g?1 at the same C-rates). Moreover, the Mg2+ and F? co-doped Li4Ti5O12 showed outstanding cycling stability, and the capacity retention was 99.62% after 150 cycles at 5C rate. Therefore, the Mg2+ and F? co-doping technique has proven an effective approach to improve the electrochemical performance of Li4Ti5O12.

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