亚微米镍钴锰三元正极材料的制备研究

发布时间：2018-03-23 12:20

  本文选题：锂离子电池　切入点：正极材料　出处：《昆明理工大学》2016年硕士论文

【摘要】：锂离子电池由于高电压、高比容量、循环性能好等特点而受到人们的广泛关注。层状三元正极材料LiNi_(1-x-y)Co_xMn_yO_2因为具有诸多优点,被认为是最有发展前景的正极材料之一。本文首先介绍了锂离子电池的研究背景、发展历史、主要特点、研究现状,然后对正极材料LiNi_(_(1/3))Co_(_(1/3))Mn_(_(1/3))O_2前驱体的合成工艺、烧结工艺进行研究,最后研究了不同表面活性剂对合成正极材料LiNi_(0.5)Co_(0.2)Mn_(0.3)O_2的影响。通过XRD、SEM、EDX、充放电测试等手段对材料的结构、形貌和电化学性能进行表征。通过超声波辅助共沉淀法合成前驱体Ni_(_(1/3))Co_(_(1/3))Mn_(_(1/3))(OH)_2,研究了不同工艺条件对制备的纳米片状前躯体Ni(__(1/3))Co_(_(1/3))Mn_(_(1/3))(OH)_2材料性能的影响。研究发现,pH值为合成前驱体过程中的关键因素。随着pH值的增加,材料的结晶度和取向都有所提高；颗粒形貌逐步向纳米片形貌转变。随着温度的升高,颗粒尺寸逐步增大,团聚程度增加。颗粒尺寸最大达到700nm左右。超声功率的提高有助于提升材料颗粒的分散度。同时超声波的引入有助于纳米片的形成。利用气氛炉常规烧结制备了具有亚微米尺寸的LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2正极材料。探讨了不同烧结温度及烧结时间对材料性能的影响。实验结果显示,在烧结时间为10h,温度为850℃C时,合成的LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2具有最为稳定的层状结构,阳离子混排效应最低,电化学性能最为优异,在1C的倍率下的首次放电容量为130mAh/g,在5C倍率下放电容量为106mAh/g,容量保持率为81.5%。通过添加不同的表面活性剂合成前驱体Ni_(0.5)Co_(0.2)Mn_(0.3)(OH)2,再通过高温固相法烧制成正极材料LiNi_(0.5)Co_(0.2)Mn_(0.3)O_2。研究了不同的表面活性剂对正极材料LiNi_(0.5)Co_(0.2)Mn_(0.3)O_2结构、形貌以及性能的影响。研究结果表明,制备的三种正极材料均为典型的α-NaFeO_2层状结构,其中,加入PVP合成的正极材料离子混排度最低。加入PVP和OA合成的前驱体均表现出明显的纳米片形貌,烧结后基本保持前驱体形貌；加入SDBS合成的前驱体表现为片状和针状形貌,烧结后为明显针状形貌。加入PVP合成的正极材料拥有最好的电化学性能。尤其是在高倍率下充放电过程中,展现出了优秀的倍率性能和循环性能。
[Abstract]:Lithium ion batteries have attracted much attention because of their high voltage, high specific capacity and good cycling performance. The layered ternary cathode material LiNi_(1-x-y)Co_xMn_yO_2 has many advantages, such as high voltage, high specific capacity and good cycling performance. It is considered to be one of the most promising cathode materials. This paper first introduces the research background, development history, main characteristics, research status of lithium ion battery, and then studies the synthesis process and sintering process of the cathode material LiNi_(_(1/3))Co_(_(1/3))Mn_(_(1/3))O_2 precursor. Finally, the effect of different surfactants on the structure of LiNi_(0.5)Co_(0.2)Mn_(0.3)O_2 was studied. The morphology and electrochemical properties were characterized by ultrasonic assisted coprecipitation method. The precursor NiSP was synthesized by ultrasonic assisted coprecipitation. It was found that the pH value of the precursor was 1 / 3 / 1 / 3 / 1 / 3 / 1 / 3 respectively. The effects of different technological conditions on the properties of the prepared nanoflake Ni(__(1/3))Co_(_(1/3))Mn_(_(1/3))(OH)_2 were studied. It was found that the pH value was the precursor of synthesis. Key factors in the body process. As pH increases, The crystallinity and orientation of the materials have been improved, and the morphology of the particles has gradually changed to the morphology of the nanocrystalline. With the increase of temperature, the particle size increases gradually. The maximum particle size is about 700nm. The increase of ultrasonic power is helpful to improve the dispersion of material particles. At the same time, the introduction of ultrasonic wave is helpful to the formation of nanocrystals. The effects of sintering temperature and sintering time on the properties of LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2 cathode materials with submicron size are discussed. When the sintering time is 10 h and the temperature is 850 鈩，

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