锂离子电池正极锰系材料的制备与性能研究

发布时间：2018-05-26 21:32

  本文选题：锂离子电池 + 正极材料　； 参考：《天津大学》2014年博士论文

【摘要】：作为新能源的锂离子电池具有比能量高、体积小、质量轻、可高速率放电、自放电率低、循环寿命长、无毒等优异性,自问世以来就受到极大的关注。目前,寻找可替代的新能源以及可用于储能的新材料已经成为人们进行科学研究的重点之一,其中锂离子电池正极材料显得尤为重要。尖晶石型Li Mn_2O_4材料具有原料资源丰富、易制备和环境友好等优点,成为锂离子电池领域研究的热点。另外,Li(Ni_(1/3)Co_(1/3)Mn_(1/3))O_2是一种极具应用前景的新型锂离子电池正极材料,它具有安全性高和低成本的优势。因此探索方便易行,环境友好的新型制备方法,对促进其实用化具有重要意义。本文采用低温水热前驱体法和低温环己酮水热制备尖晶石LiMn_2O_4,并且详细研究了影响低温环己酮水热法制备的LiMn_2O_4的各个因素。此外,采用简单两步法合成了三元材料Li(Ni_(1/3)Co_(1/3)Mn_(1/3))O_2,并对其影响因素进行了初步的探讨。通过X射线粉末衍射(XRD)、扫描电镜(SEM)等测试手段对样品的结构和形貌进行表征,对采用不同方法合成的正极材料的合成条件进行了研究,利用首次充放电和循环性能测试,来考察材料的电化学性能。通过研究发现,在低温前驱体法中,水热反应温度120℃,加热12 h,然后在100℃,干燥12 h,得到前驱体β-MnO_2粉末,最后在800℃,煅烧10 h合成的LiMn_2O_4性能最佳。采用低温环己酮水热法,水热温度110℃,反应8 h,同时控制Li/Mn的摩尔比为1.1:1,以及环己酮与蒸馏水的比为2:25时,此时制备出的样品尖晶石LiMn_2O_4具有最优的电化学性能。合成三元材料Li(Ni_(1/3)Co_(1/3)Mn_(1/3))O_2的最优条件为:在60℃,制备出前驱体Ni_(1/3)Co_(1/3)Mn_(1/3)(OH)2,在Ar气保护下,混合一定比例的LiOH·H2O,通气,先加热450℃预烧4 h,然后在850℃煅烧6 h。尽管尖晶石LiMn_2O_4有很多优点,但是它的导电性差限制了它在在大功率应用程序中的使用。另外,正极材料LiMn_2O_4在循环过程中存在严重的容量衰减,则是另一个具有挑战性的问题,同时也是阻碍了LiMn_2O_4的商业化。因此,必须对LiMn_2O_4进行改性。碳包覆是一种有效的改性手段,可以改善活性物质颗粒之间以及活性物质与导电剂之间的导电性。文中利用XRD、SEM、电化学测试等手段研究不同碳源、碳包覆量、煅烧温度等因素对合成产品各种性能的影响,研究结果表明针对低温环己酮水热法,葡萄糖为最佳碳源,添加10%的葡萄糖,在600℃煅烧4 h合成的LiMn_2O_4/C具有最好的电化学性能。
[Abstract]:As a new energy source, lithium ion batteries have many advantages, such as high specific energy, small volume, light weight, high rate of discharge, low self-discharge rate, long cycle life, non-toxic and so on. At present, the search for new energy sources and new materials for energy storage has become one of the focuses of scientific research, among which the cathode materials for lithium ion batteries are particularly important. Spinel Li Mn_2O_4 has become a hotspot in the field of lithium-ion batteries due to its rich raw material resources, easy preparation and environmental friendliness. In addition, this new type of cathode material for lithium-ion batteries has the advantages of high safety and low cost. Therefore, it is of great significance to explore a new and convenient and environmentally friendly preparation method to promote its practicality. In this paper, spinel limn _ 2O _ 4 was prepared by low-temperature hydrothermal precursor method and low-temperature cyclohexanone hydrothermal method. The factors affecting the preparation of LiMn_2O_4 by low-temperature cyclohexanone hydrothermal method were studied in detail. In addition, a simple two-step method was used to synthesize the ternary material Lian Nihe / T 1 / 3 Cos / T / 1 / 3 / 3 / 1 / 3 / 3 / 1 / 3 / 3 / 1 / 3 / 3 / 1 / 3 / 1 / 3 / 3 / 1 / 3 / 1 / 3 / 1 / 3 / 1 / 3 / 1 / 3 / 3 The structure and morphology of the samples were characterized by means of X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). The synthetic conditions of the cathode materials synthesized by different methods were studied. To investigate the electrochemical properties of the materials. It was found that the precursor 尾 -MnO _ 2 powder was obtained by hydrothermal reaction at 120 鈩，

本文编号：1938955