高振实密度多孔钛酸锂微球的合成工艺及其性能研究

发布时间：2018-01-12 10:02

  本文关键词：高振实密度多孔钛酸锂微球的合成工艺及其性能研究　出处：《苏州大学》2014年硕士论文　论文类型：学位论文

  更多相关文章： 锂离子电池 钛酸锂 喷雾干燥 振实密度 多孔结构

【摘要】：钛酸锂作为锂离子电池负极材料,具有“零应变”、安全性高等优点,受到了人们越来越多的关注。然而钛酸锂的电导率和振实密度很低,限制了它的大规模应用。在提高钛酸锂的电导率方面已有大量研究,主要采用纳米化、表面包覆和金属元素掺杂等方法。但在提高钛酸锂的振实密度方面的研究却很少。本文采用喷雾干燥技术,以碳酸锂和锐钛矿型二氧化钛为原料通过二次煅烧法制备了振实密度高、循环性能好的多孔钛酸锂微球负极材料。二次煅烧法的目的是在喷雾干燥前先将原料混合煅烧,除去反应生成的气体形成前驱体产物,喷雾干燥后形成由一次颗粒组成的松散球形前驱体,经再次煅烧,球形前驱体在高温下收缩、熔融生长成既彼此相连又有介孔阻隔的球形钛酸锂材料。由此法制备的钛酸锂负极材料振实密度可达1.20 g cm-3,比一次煅烧法制备的钛酸锂振实密度(0.89 g cm-3)高出近1.4倍。而且,用此法制备的钛酸锂材料,因球形粒子内有介孔存在而非常有利于电解液渗透,又因组成球形颗粒的一次粒子彼此相连而减少了接触电阻,所以由此钛酸锂负极材料制备的锂离子电池具有非常优异的循环性能。在1 C下充放电,循环400圈后的容量保持率仍为98.35%。我们还对喷雾干燥条件、煅烧温度、时间进行了系统研究。发现在料液浓度为0.28 g mL-1时,第二次煅烧在850℃下进行8 h得到的高振实密度多孔钛酸锂微球(LTO-850),其综合性能最优。此外,还对LTO-850微球进行改性研究,包括:通过调整原料的Li:Ti摩尔比获得TiO2-Li4Ti5O12微球;LTO-850微球电极不添加导电剂;球形前驱体在不同气氛下(空气,H2-Ar混合气)经过煅烧得到样品;钛酸锂的高低温性能等内容。
[Abstract]:Lithium titanate, as a cathode material for lithium ion batteries, has attracted more and more attention due to its advantages of "zero strain" and high safety. However, the conductivity and vibrational density of lithium titanate are very low. A lot of research has been done to improve the conductivity of lithium titanate, which is mainly nanocrystalline. The methods of surface coating and metal element doping are few in improving the vibrational density of lithium titanate. Spray drying technique is used in this paper. Lithium carbonate and anatase titanium dioxide were used as raw materials to prepare high vibrational density by secondary calcination. The aim of the secondary calcination method is to mix the raw materials before spray drying and to remove the gases generated by the reaction to form precursor products. After spray drying, a loose spherical precursor composed of primary particles was formed. After re-calcination, the spherical precursor shrank at high temperature. A spherical lithium titanate material with interlinked mesoporous barrier was prepared by melt growth. The vibrational density of lithium titanate anode prepared by this method can reach 1.20 g cm-3. The vibrational density of lithium titanate prepared by the single calcination method is nearly 1.4 times higher than that of the lithium titanate prepared by this method. Because of the existence of mesoporous particles in the spherical particles, the electrolyte permeation is very favorable, and the contact resistance is reduced because the primary particles that make up the spherical particles are connected with each other. Therefore, the lithium ion battery prepared from the lithium titanate anode material has excellent cycling performance. It is charged and discharged at 1C. The capacity retention rate was 98.35 after 400 cycles. We also studied the spray drying conditions, calcination temperature and time. It was found that the concentration of the liquid was 0.28 g mL-1. The high density porous lithium titanate microspheres (LTO-850) obtained by the second calcination at 850 鈩，

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