Structural and electrochemical evaluation of bismuth doped lithium titanium oxides for lithium ion batteries

Micro-sized Li4Ti5-xBixO12 (0 <= x <= 0.15) materials are synthesized using a simple solid state method in air. The structural, morphological, and electrochemical characteristics of Bi-doped lithium titanates and pristine samples are methodically analyzed by X-ray diffraction (XRD), Raman spectroscopy, field emission-scanning electron microscopy (FE-SEM), and electrochemical impedance spectroscopy (EIS). The XRD and Raman spectroscopy results demonstrate that bismuth-doping do not alter the spinel structure and good crystalline materials are synthesized. The FE-SEIVI images show that all samples possess the same morphological characteristics, with a particle size distribution of 0.5-1 mu m. The electrochemical cycling testing reveals that the Li4Ti4.9Bi0.10O12 sample exhibits discharge capacities of 205.4 mAh g(-1), 160.8 mAh g(-1) and 135.4 mAh g(-1) after 50 cycles at 1C, 5C, and 10C-rates, respectively. The differential capacity curves suggest that the Li4Ti4.9Bi0.10O12 sample has a weaker polarization effect than the other samples. The EIS measurements imply that the Li4Ti4.9Bi0.10O12 sample possesses a high electronic conductivity and lithium ion diffusivity, which demonstrate that this new Li4Ti4.9Bi0.10O12 material would be a good candidate as an anode for lithium ion batteries. (C) 2015 Elsevier B.V. All rights reserved.