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Gu Y.-J.,Shandong University of Science and Technology | Gu Y.-J.,Rizhao Huaxuan New Energy Co. | Guo Z.,Shandong University of Science and Technology | Liu H.-Q.,Shandong University of Science and Technology
Electrochimica Acta | Year: 2014

Li4Ti5O12 is a highly promising anode material for use in Li-ion batteries. Herein, Li4Ti5O 12 samples are prepared by sintering Li2CO3 and anatase TiO2 with varying Li molar excess. Characterization by AC impedance spectroscopy, X-ray diffraction spectroscopy and scanning electron microscopy is performed. The electrochemical performance, crystal structure and surface morphology are found to be dependent on the Li content. The effect of TiO2 and Li2TiO3 impurities in Li 4Ti5O12 on electrochemical characteristics including charge-discharge cycling and the AC impedance spectra is also investigated. These two impurities are found to have different effects on the electrochemical properties of Li4Ti5O12. At a 2% molar Li excess, a high capacity and Li ion diffusion coefficient are achieved. © 2014 Elsevier Ltd. Source


Gu Y.-J.,Shandong University of Science and Technology | Li Y.,Shandong University of Science and Technology | Fu Y.,Shandong University of Science and Technology | Zang Q.-F.,Shandong University of Science and Technology | And 5 more authors.
Electrochimica Acta | Year: 2015

Abstract We synthesized LiNi0.5Mn1.5O4 cathode materials by using ammonia-mediated carbonate precipitation, and we studied how the ammonia concentration during synthesis (0.1-0.5 mol/L) affected the structural, physicochemical, and electrochemical characteristics of the prepared materials. X-ray diffraction and Rietveld refinement reveal that the amount of Li/Ni antisite defects in the LiNi0.5Mn1.5O4 depend much on the ammonia concentration. The LiNi0.5Mn1.5O4 prepared at 0.3 mol/L has the fewest Li/Ni antisite defects. This sample also delivers the best electrochemical performance, retaining a capacity of 133.5 mAh g-1 after 20 cycles at 0.1 C. Electrochemical impedance spectroscopy confirms that the LiNi0.5Mn1.5O4 prepared at 0.3 mol/L has lower charge transfer resistance, correlating with its better ion diffusion kinetics than the other materials. © 2015 Elsevier Ltd. Source


Gu Y.-J.,Shandong University of Science and Technology | Zhang Q.-G.,Shandong University of Science and Technology | Zhang Q.-G.,Pulead Technology Industry Co. | Chen Y.-B.,Shandong University of Science and Technology | And 10 more authors.
Journal of Alloys and Compounds | Year: 2015

Layered Li1+ xNi0.5Co0.2Mn0.3O2 (x = 0, 0.02, 0.04, 0.06, 0.08) materials were synthesized using the co-precipitation method. Rietveld refinements measurements reveal that the concentration of Ni2+-3b ions decreases from 0.06 to 0.043, with x changing from 0.02 to 0.08. The initial coulombic efficiency improves with the increase in the content of Li-excess because the content of Ni at the 3b site decreases with the increase of Li-excess in the samples from 0 to 0.08. The analysis indicates that Li1.08Ni0.5Co0.2Mn0.3O2 exhibits the largest diffusivity value due to the dependence of the diffusion coefficient of lithium ions on the content of Ni in the 3b sites. © 2015 Published by Elsevier B.V. Source


Gu Y.-J.,Shandong University of Science and Technology | Gu Y.-J.,Rizhao Huaxuan New Energy Co. | Zang Q.-F.,Shandong University of Science and Technology | Liu H.-Q.,Shandong University of Science and Technology | And 5 more authors.
International Journal of Electrochemical Science | Year: 2014

LiNi0.5Mn1.5O4 is synthesized using Ni0.5Mn1.5(CO3)2, which is prepared by a carbonate co-precipitation method at pH values of 7.5, 7.8, 8.0 and 8.3. The Rietveld refinements reveal Li and Ni site substitution in LiNi0.5Mn1.5O4. The preparation pH is found to affect Li and Ni site substitution in LiNi0.5Mn1.5O4. For the compound prepared at a pH of 8.3, high capacity and a high Li ion diffusion coefficient are achieved. © 2014 The Authors. Source

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