【作者】 张海峰；

【导师】 单忠强；

【作者基本信息】 天津大学 ， 应用化学， 2009， 硕士

【摘要】 锂离子电池是90年代后投放市场的新一代绿色环保电池,它因为电压高、自放电率低、体积小、重量轻、无记忆效应等独特性能被广泛应用于便携式电器以及电动自行车中。目前商品化的锂离子电池广泛采用的负极材料是石墨类碳材料,但由于碳/石墨第一次充放电时,会在碳表面形成钝化膜,造成容量损失;而且碳的电极电位与锂的电位很接近,当电池过充电时,金属锂可能在碳电极表面析出,形成枝晶而引发安全性问题。而Li4Ti5O12作为锂离子电池负极材料在充放电时结构几乎不发生变化被称为“零应变”材料,具有非常优越的循环性能。钛酸锂具有原料来源广泛、价格低廉、热稳定性好、比能量高、循环性能好、安全性能突出等特点。其理论容量为175mAh/g,工作电压为1.5 V左右,是很具潜力的负极材料之一。本文采用溶胶-凝胶法,以草酸和柠檬酸为调节剂,制备出了尖晶石Li4Ti5O12,研究了调节剂与钛酸丁酯的比例和烧结时间对产物电化学性能的影响。结果表明当调节剂草酸与钛酸丁酯的摩尔比为1.0时,在800℃烧结20h的产物粒度为400nm左右,在0.1C倍率下,首次放电比容量为145.9 mAh/g,30次循环后放电比容量为125.8mAh/g。当调节剂柠檬酸与钛酸丁酯的摩尔比为0.5时,在850℃烧结24h的产物粒度为450nm左右,在0.1C倍率下,首次放电比容量为144.5 mAh/g,30次循环后放电比容量为125.9mAh/g。本文采用了液相水热法制备出了Li4Ti5O12材料,并采用XRD、SEM等手段对材料进行表征,测试了材料的电化学性能。结果表明,以氢氧化锂为锂源在700℃下锻烧10 h制得的样品表现出较好的电化学性能,0.1C的倍率下首次放电比容量为115.4mAh/g,20次循环后放电比容量为101 mAh/g。本文对材料进行了掺杂金属钼的研究,实验结果表明,掺杂产物的主要成分为反应新生成的化合物NaLiTi3O7和Li2MoO4以及未反应完全的Na2MoO4,当钼酸钠和醋酸锂的摩尔比为1:3和0.6:3.4/3时制备出的材料良好的电化学性能,在0.1C倍率下,首次放电比容量分别为157.5 mAh/g和145.5mAh/g,20次循环后放电比容量分别为为137.5mAh/g和95mAh/g。更多还原

【Abstract】 Lithium ion battery is a new generation green non-pollution battery when it was used in the 1990s. It is widely used in portable electron apparatus and cars due to its highlights, such as high voltage, low discharge rate by itself, little volume, light weight and nonmemeory effect, but the anode materials for lithium ion batteries are the key to constrain its whole performance. The negative-electrode materials are usually carbon in commercial lithium ion batteries. But when discharge for the first time, there are passivation membrane on the surface of carbon, which will cause capacity lose. Moreover, the potential of carbon is very close to that of lithium, when overcharge, the metal lithium will separate out on the surface of carbon, which is the intrinsic safety we must concern. While, for Li4Ti5O12, when used as negative material for Lion battery, there is no such concerns, and during the process of Li+ intercalation and de-intercalation, its crystal form does not change and the total volume change is less than 1%, so it is regarded as a“zero strain”material. It has many characteristics, such as a wide range of raw materials, low cost, good thermal stability, high specific energy, good recycling performance and outstanding features such as security. So Li4Ti5O12 is one of the most potential anode materials which has a high theoretical capacity (175mAh/g) and voltage (about 1.5V versus Li/Li).Li4Ti5O12 powders was successfully synthesized by a sol–gel method using oxalic acid and citric acid as a chelating agent. The effect of amount of chelating agent, calcination time on electrochemical performance of product was investigated. In our study, the sample synthesized at 800℃for 20h with oxalic acid to titanium molar ratio R=1.0 yielded the best capacity of 145.9 mAh/g and 140 mAh/g for the first cycle and the 30th cycle respectively at a current density of 0.1C. The sample synthesized at 850℃for 24h with citric acid to titanium molar ratio R=0.5 yielded the best capacity of 144.5 mAh/g and 125.9mAh g-1 for the first cycle and the 30th cycle respectively at a current density of 0.1C.Li4Ti5O12 was obtained by hydrothermal method. The Li4Ti5O12 was characterized by XRD, SEM analysis. We also studied the electrochemical properties of the product. The results indicated that the sample which use Lithium hydroxide as lithium sourcesintered at 700℃for 10 hours showed the best electrochemical properties. The discharge capacity was 141.8 mAh/g and 125.9 mAh/g for the first cycle and the 20th cycle respectively at a current density of 0.1C at a current density of 0.1C. This paper carried out on materials doped molybdenum metal research, experimental results show that Major components of doping products generated was responsed new compounds NaLiTi3O7 and Li2MoO4 as well as unreacted Na2MoO4.When molar ratio of sodium molybdate and lithium acetate is 1:3 and 0.6:3.4 / 3, the material show a good electrochemical performance, The discharge capacity was 157.5 mAh/g and 145.5 mAh/g for the first cycle at a current density of 0.1C ,and after 20 cycle the discharge capacity was 137.5 mAh/g and 95 mAh/g.更多还原