【作者】 张金歌；

【导师】 杨长春；

【作者基本信息】 郑州大学 ， 物理化学， 2010， 硕士

【摘要】 尖晶石型Li4Ti5O12作为锂离子电池的负极材料,由于电化学性能优良、环境友好、成本低廉等突出优点,被称为“零应变”材料,并引起很多科研工作者及企业的足够重视。本文对具有尖晶石结构Li4Ti5O12材料进行研究,分别利用高温固相法、溶胶—凝胶法、水热法制备了电极材料Li4Ti5O12。分别研究了煅烧时间、焙烧温度、原料配比对电极材料性能的影响。一、CH3COOLi·2H2O与无定形TiO2分别在800℃煅烧不同时间,合成Li4Ti5O12。研究发现：利用固相法烧结样品时,800℃烧结15h,能够合成纯相Li4Ti5O12,0.1C恒流充放电条件下首次放电比容量为146mAh·g-1,是理论值的83%。微波煅烧电化学性能较优越,O.1C首次放电比容量达到151mAh·g-1,但不适于大规模生产。同时还对样品A15进行了碳包覆,蔗糖为碳源,当C:Li4Ti5O12=6：94时,比容量最大,首次放电比容量达到157mAh·g-1,碳的添加,提高了Li4Ti5O12的导电性。二、溶胶—凝胶法制备样品,TiO(C4H9)4与CH3COOLi·2H2O为原料,乙酰丙酮为螫合剂,无水乙醇为溶剂,制备凝胶。通过对比试验发现：溶剂的用量及水解反应温度对凝胶时间影响较大,当TiO(C4H9)4与无水乙醇体积比为1：8,水解反应温度40°C,凝胶时间控制在5h,制备得到的凝胶较好。利用TG-DSC、XRD、SEM、恒流充放电、循环伏安等测试方法对制备条件进行了讨论,研究发现：煅烧时间的长短直接影响产物的纯度,800℃烧结15h合成得到尖晶石Li4Ti5O12的单一相,产物颗粒粒度较小,分布比较均匀,0.1C首次放电比容量为155mAh·g-1,但是1C放电比容量就只有121mAh·g-1,样品的大倍率充放电性能不是很理想。三、目前水热法大量应用于锂离子电池正极材料的制备中,但很少有水热法制备负极材料的报道。钛酸四丁酯和醋酸锂为起始原料,乙酰丙酮为螯合剂,硫酸铵为电解质,采用水热法合成了纳米级尖晶石Li4Ti5O12的单一物相。当锂过量100%时,能够得到均一物相尖晶石型Li4Ti5O12,0.1C首次放电比容量为160mAh·g-1四、本论文还组装了Li4Ti5O12/LiCoO2实验电池,O.1C恒流充放电测试首次放电比容量达到142mAh·g-1更多还原

【Abstract】 While, for Li4Ti5O12, which had been used as anode materials for lithium ion batteries, there were almost no structure change during discharge and charge. We called it "Zero strain" material, that was why there was very small irreversible capacity lose. Li4Ti5O12 gave rise to many researchers and companies enough attentons, whch was due to its highlights, such as excellent electrochemical performances, environmentally friendly, low cost.In this paper, we worked over the preparation of spinel structure material Li4Ti5O12, which was prepared by solid state method, sol-gel method and hydrothermal method. We also studied the factors, which affected electrochemical performances, such as the calcining time, calcination temperature, molar ratio of lithium to titanium.The first one, we prepared the precursor by CH3COOLi·2H2O and amorphous TiO2. The studies manifested that with solid state method, the pure spinel structure material Li4Ti5O12 could be synthesized by calcinated the precursor at 800℃for 15h in the air in the muffle, and the first discharge specific capacity was 146mAh·g-1 at 0.1C, which was 83% of the theoretical capacity. The sample which was calcination by Microwave had better electrochemical performance, initial discharge specific capacity was 151mAh·g-1 at 0.1C. But it was not suitable for mass production. In order to increase the specific capacity of Li14Ti5O12, we coated sucrose solution of Li4Ti5O12, initial discharge specific capacity increased to 157mAh·g-1 at 0.1C. The addtion of carbon improved the conductivity of Li4Ti5O12.The second one, we synthesized Li4Ti5O12 by sol-gel method, discussed the conditions of the reaction. The gelation was good while the volume ratio of TiO(C4H9)4 and CH3CH2OH was 1:8, and the temperature of hydrolysis was 40℃. The precursor was analysed by TG-DSC, at the same time, we discussed the synthesis conditions by XRD, SEM, charge and discharge tests and cycle voltammogram tests. We founded that calcination time affected the purity of the products. The results showed that the spinel structure material Li4Ti5O12 could be synthesized at 800℃for 15h with TiO(C4H9)4 and CH3COOLi·2H2O as raw materials. The sample synthesized at 800℃for 15h had good crystal, unformly distributed, and initial discharge specific capacity was 155mAh·g-1 at 0.1C, But the discharge capacity was only 121mAh·g-1 at 1C, samples of the large charge and discharge performances were not satisfactory.The third one, we synthesized Li4Ti5O12 by hydrothermal method. At present, the hydrothermal method had been widely used to prepare cathode materials for lithium ion batteries, but few reported to prepare anode materials. It showed that the nanometer spinel material Li4Ti5O12 could be synthesized at 800℃for 15h with TiO(C4H9)4 and CH3COOLi·2H2O as raw materials. When the lithium was excessed 100%, initial discharge specific capacity was 160mAh·g-1 The last one, we also assembled Li4Ti5O12/LiCoO2 test battery, and the initial discharge specific capacity was 142mAh·g-1 at 0.1C.更多还原