锂离子电池正极材料锂锰氧的研制

【作者】 姚耀春；

【导师】 戴永年； 杨斌；

【作者基本信息】 昆明理工大学 ， 有色金属冶金， 2003， 硕士

【摘要】 随着电子设备的快速发展以及能源与环境问题的日益突出，人们对化学电源提出了更高的要求。锂离子电池以其高电压、比能量大、循环寿命长，无污染等优点而得到广泛的应用。具有高插入电位的过渡金属氧化物常用作锂离子电池的正极材料，目前研究较多的是层状结构的LiCoO₂、LiNiO₂。以及尖晶石结构的LiMn₂O₄。已商业化的LiCoO₂正极材料由于Co资源有限，价格昂贵，其应用受到限制，尤其在动力电源和固定储能设备方面的应用。LiNiO₂也因制备时控制条件要求高，而未能实现工业化。尖晶石结构的LiMn₂O₄以其高电压、高安全性、低成本、易回收、对环境友好等优点而被人们公认为最具应用前景的锂离子电池正极材料。 本文在综述锂离子电池及其相关材料的基础上，分析了国内外尖晶石LiMn₂O₄的研究现状，可知LiMn₂O₄正极材料的不足之处在于材料的均匀性不好，合成产物物相多，结构不稳定，从而导致材料性能差。尽管许多研究工作者做了大量的研究，开发了溶胶—凝胶法、融盐浸渍法、Pechini法以及其它方法来制备LiMn₂O₄正极材料，并使材料的性能在一定程度上有所提高，但由于这些方法不是工艺复杂，就是成本较高，不适于大规模化生产。因此研究开发既能应用于工业化生产，又能制备出具有优良电化学性能的尖晶石LiMn₂O₄工艺路线依然是当前锂离子电池正极材料研究工作的重中之重。 为了适应工业化的需要，又能改善材料的性能。本研究在传统的高温固相合成法基础上，引入机械活化的方法，采用机械活化——高温固相法制备了标准尖晶石LiMn₂O₄并将TG、DSC、XRD、SEM等检测手段和电化学分析方法相结合，对材料的热力学性质、物理化学性能以及电池的制作技术进行了研究。 研究表明：合成温度、合成时间、原料配比、热处理制度以及产物粒度是影响产物性能的重要因素。随着合成温度和时间的增加，产物的结构和晶型越趋于完善，但在1100℃得到的产物有烧结和晶粒增大的现象，恒温时间超过24h后对材料的性能影响不是很大；Li／Mn比在0.95～1.05／2的条件下都可得到标准的尖晶石LiMn₂O₄，尤其当Li／Mn比为1.05／2时，所合成的材料具有较好的电化学性能；通过两段合成法制备的产物性能要比一段合成法法制备的产物性能好，而两段间隔合成法比两段连续合成法处理的材料性能更佳；颗粒的粒度随着球磨时间的延长而减小，比表面昆明理工大学硕士学位论文摘要却增大，粒度小且分布范围窄的材料有利于铿离子的扩散。 在合成材料的同时，本文还对铿离子电池的组成和制作工艺进行了探讨，分析了制浆、涂布、装配、化成几个主要工序对电池性能的影响，还重点对铿离子电池正极各物质的配料进行了优化研究。结果表明，正极极片中PVDF粘接剂和乙炔黑导电剂的添加量只有适量的时候，正极极片的充放电性能才较好。本研究中PVDF粘结剂的添加量在7一10%，乙炔黑导电剂的添加量在8%左右，正极极片的性能最佳。更多还原

【Abstract】 With the rapid development of electronic facilities as well as energy and environmental concerns, people have made high demands on batteries. Li-ion batteries are widely used for their favorable advantages of high voltage, big specific capacity, long cycling life and non-pollution. Transition metal oxides with high inserted potential are used as cathode material of Li-ion batteries generally. At present, layered compounds LiCo02 , LiNi02 and spinel LiMn204 are extensively studied. However, the application of commercialized LiCo02 is limited due to the lackness and high expense of raw material Co, especially in power battery and large-scale energy storage device. The industrialization of LiNi02 can not come true .because the conditions of control are out of reach on preparation. Spinel LiMnA is considered as the most promising positive material for Li-ion batteries because of its high voltage ,high safety, low cost,easy recycle and environmental affinity.Based on summarizing Li-ion Batteries , some pertinent data and looking into the status quo about spinel LiMnA research at home and abroad , it’ s known that the deficiency of the material lies in inhomogeneity .motley phase .instability as well as poor reversibility. Now, many studies and methods , such as sol-gel, welt-impreghation and Pechini method, etc, have been making to synthesize LiMn204 cathode material by reserchers. To some extent, the properties of the material are improved. Nevertheless, these methods are not u,sed- for mass production because of complicated technics or high cost. So the emphasis of our investigations is to develop a technics which can both be fit for industrialization and synthesize spinel LiMn204 with excellent electrochemical characteristics.For adapting to the need of industrialization and improving the properties of materials,the method of mechanical activation has introduced on the basis of traditional calcinations at high temperature.The stardardspinel LiMn204 is prepared by the mechanical activation-high temperature solidsynthesis method.The thermodynamic property , the physical-chemistry performance and the producing techniques of .battery have been studied by means of thermogravimetry (TG), differential scanning calorimetry (DSC), x-ray diffraction(XRD) , scanning electric microscopy (SEM) as well as various electrochemical analysis methods.Studies show that synthesis temperature, calcinations time, recipe of raw materials, heat treatment and particle size of products are main factors affecting the performances of LiMn204 cathode materials. With the increment of synthesis temperature and time, the structure and crystal of products are getting to perfect. But the samples synthesized at 1100 "C appears the phenomena of sinter and microcrystal growth. When the time of constant temperature exceeds 24 hours,the heating time has little influence on the performance of products. The standard spinel structure of LiMn204 can be obtained at the Li/Mn mole ratio of 0. 95~1. 05/2, especially, at the ratio of 1.05/2, the synthesized samples have better electrochemical characteristics.The materials synthesized by two steps heat treatment have preferable performance. Comparing the two continuous calcination method with the two discontinuous calcination, the former is the better. With prolongation of ball milling time, particle size decreases, but specific surface area increases. Small and narrow particle size distribution benifit diffusion of Li-ion.Also, the production techniques of Li-ion battery is discussed, the influence of important working proceduces (including the preparing, the doping, the assembling , etc.) on battery performance is analysed and the recipe of cathode materials is optimized. The results give that the positive plate takes on preferable charge-discharge properties only when the amount of additive of PVDF and acetylene black is suitable. When the amount of PVDF and acetylene black is 7~10% and 8%, the positive plate obtained possesses optimum properties in our studies.更多还原