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Preparation and Characterization of Lithium Titanate Anode Material Synthesized by a Wet Chemical Method

Author: WangXuanYu
Tutor: LiYunZuo
School: Central South University
Course: Metallurgical Engineering
Keywords: Lithium ion batteries Anode material Spinel Li4Ti5O12 Low-temperature wet chemical mothod Grain growth
CLC: TM912
Type: Master's thesis
Year: 2013
Downloads: 2
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Abstract


Spinel Li4Ti5O12is considered to be one of the most promising anode materials for lithium ion batteries, because of its stable structure, high safety, flat charge and discharge voltage and excellent cycle performance, it has been attracted more and more widely attention all over the world. In this paper, the well-crystallized spinel Li4Ti5O12with high purity and good cycle properties was successfully synthesized by two different wet-chemical methods at low temperature. The physical and electrochemical performances of as prepared Li4Ti5O12samples were characterized by themogravimetry and differential thermal analysis (TG-DTA), X-ray diffraction (XRD), scanning electric microscope (SEM) and constant current discharge-charge measurement.Spinel-type lithium and titanium composite oxide Li4Ti5O12was successfully synthesized via one-step hydrolysis method followed by calcination using titanium tetrachloride (TiCl4) and lithium hydroxide (LiOH·H2O) as raw materials. The effect of many factors on phase composition and structure were investigated. The results showed that the phase-pure Li4Ti5O12with well spinel structure can be obtained under the optimal conditions as follows:LiOH solution concentration is2.0mol/L, theoretical LiOH dosage, hydrolysis temperature is50℃, and the precursor was calcined at800℃for6h. The constant current discharge-charge tests showed that the phase-pure Li4Ti5O12material shows an initial discharge specific capacity of178mAh/g at0.1C rate; the capacity of the sample remains at93.8%(150mAh/g) of its initial specific capacity (160mAh/g) after60cycles at a current density of0.5C, exhibiting the excellent cycle performance of Li4Ti5O12.On the basis of one-step hydrolysis method, Li-Ti-O precursor was synthesized by wet chemical method in aqueous media using amorphous hydrated TiO2, which was prepared by neutralizing hydrolysis from TiCl4aqueous solution in ammonia solution. The results showed that the optimal conditions of synthesizing Li-Ti-O precursor by two-step method were as follows:LiOH solution concentration is1.0mol/L, LiOH dosage is2.5-3times of the theoretical dosage, and synthesis time is2h. The products had a good spinel structure after calcined in the range of700～900℃. The sample calcined at750℃for6h showed the best electrochemical performance. The tests showed that the as-prepared Li4Ti5O12delivers the initial discharge specific capacity of175mAh/g at0.1C current rate in the voltage range of1.0to2.5V, and its discharge capacity reduce to167.5mAh/g at0.5C. The capacity decay to163mAh/g after60cycles, and remain97.3%of its initial specific capacity at0.5C rate, indicating that spinel Li4Ti5O12prepared by two-step method has the excellent cycle performance.In this paper, the process of Li4Ti5O12grain growth during heat treatment was also studied combined the dynamic equation on the basis of the diffusion controlled growth mechanism. The results showed that the grain growth exponent n≈4at700℃, the grain growth rate constant k=3.9894×104nm4/min, and the apparent activation energy of grain growth E=196.84kJ/mol in the range of500～800℃。

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