锂离子电池正极材料锰酸锂的制备及其改性研究

发布时间：2018-06-03 17:40

本文选题：锂离子电池 + 尖晶石型锰酸锂　；参考：《齐鲁工业大学》2015年硕士论文

【摘要】：随着电子设备行业的迅猛发展以及能源枯竭和环境污染等问题的日趋明显,人们对化学电源的要求越来越高。尖晶石型结构的锰酸锂(LiMn2O4)因其丰富的资源来源、廉价的成本、无污染等优势,是近期发展现状下锂离子行业最有发展前景的正极材料。尖晶石型结构的锰酸锂(LiMn2O4)因为诸多因素的影响,电池的性能还不是很好,因此改善其性能成为研究热点。以廉价的碳酸锂(Li2CO3)和二氧化锰(MnO2)为原料,采用高温分段烧结相结合的方法,合成纯相尖晶石型结构的锰酸锂(LiMn2O4)正极材料。本文通过差热热重分析(TG-DSC)实验,确定纯相尖晶石型结构的锰酸锂(LiMn2O4)的烧结温度；通过X射线衍射(XRD)和扫描电镜(SEM)测试,表征纯相尖晶石型结构的锰酸锂(LiMn2O4)的结构和微观形貌；通过充放电测试实验,研究合成的纯相尖晶石型结构的锰酸锂(LiMn2O4)的综合电化学性能。本文主要是通过以下方法对锰酸锂进行改性研究：(1)改进合成方法(2)体相掺杂改性(3)材料表面包覆改性。在改进合成方法研究方向,主要是采取对原材料进行球磨的方法且首次研究球磨对锰酸锂(111)晶面的影响。球磨后合成的尖晶石型结构的锰酸锂(LiMn2O4)的性能更为优异,在球磨时间为6小时时达到最佳值(在0.5C倍率下首次充放电为129.3 mAh/g,30循环后容量保持率为94.95%),且研究表明球磨后可以改变锰酸锂(111)晶面的大小从而影响锰酸锂的电化学性能。在体相掺杂改性方向,研究Ni、Co、Al、F等阴阳离子单独掺杂对锰酸锂电化学性能的影响以及A1、F阴阳离子复合掺杂对锰酸锂电化学性能的影响。研究表明,Ni、Co、Al等阳离子单独掺杂改性锰酸锂,首次充放电都是减小的,但是循环保持率明显提高；F离子单独掺杂改性锰酸锂,首次充放电是增加的且循环保持率较好；A1、F阴阳离子复合掺杂改性锰酸锂不但可以保持首次充放电的大小且可以提高其循环保持率。在材料表面包覆改性方向,研究硅溶胶表面包裹改性对锰酸锂电化学性能的影响。研究表明,硅溶胶表面包裹改性锰酸锂后,在锰酸锂的表面形成了一层包裹相,随着硅溶胶加入量的增加,样品(LiMn2O4)的放电比容量是减小的而容量保持率是先增加后减小,当硅溶胶加入量小于2.0wt%时,样品(LiMn2O4)的容量保持率由92.241%增加到了94.068%,但当硅溶胶加入量大于2.0wt%时,样品的容量保持率开始减小
[Abstract]:With the rapid development of electronic equipment industry and the increasingly obvious problems such as energy depletion and environmental pollution, people are demanding more and more chemical power supply. Spinel LiMn2O4 is the most promising cathode material in lithium ion industry due to its abundant resource sources, low cost and no pollution. Spinel LiMn2O4) because of the influence of many factors, the performance of the battery is not very good, so improving its performance has become a research hotspot. LiMn2O4) cathode material with pure spinel structure was synthesized from cheap lithium carbonate (Li _ 2CO _ 3) and manganese dioxide (mn _ 2O _ 2). The sintering temperature of pure spinel LiMn2O4 (LiMn2O4) was determined by differential thermogravimetric analysis (TG-DSCC), and the structure and microstructure of pure spinel LiMn2O4 were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical properties of pure spinel LiMn2O4 were studied by charge-discharge test. In this paper, the modification of lithium manganese oxide by the following methods is studied. In the research direction of improving the synthesis method, we mainly adopt the method of ball milling of raw materials and study the effect of ball milling on the crystal plane of lithium manganese oxide (111) for the first time. The spinel structure LiMn2O4) prepared by ball milling has better properties. When the milling time is 6 hours, the optimum value (the first charge and discharge at 0.5C rate is 129.3 mg 路g / g ~ (30) cycle capacity retention rate is 94.95%, and the study shows that the size of crystal plane can be changed after ball milling, thus affecting the electrochemical performance of lithium manganese oxide. In the direction of bulk doping modification, the effect of the single doping of anionic and anion ions, such as NiCoCoAlF, on the electrochemical properties of lithium manganese oxide and the influence of the composite doping of A _ (1) O _ (F) ions on the electrochemical properties of lithium manganese oxide were studied. The results show that the initial charge and discharge rate of modified lithium manganate is decreased, but the cyclic retention rate of F ion is obviously increased. The first charge / discharge rate is increased and the cyclic retention rate is better. The modified lithium manganese oxide doped with anion and anion can not only keep the size of the first charge and discharge but also improve the recycling retention rate. The effect of surface encapsulation modification of silica sol on the electrochemical properties of lithium manganese oxide was studied. The results show that a layer of encapsulation phase is formed on the surface of lithium manganese oxide coated with silica sol. With the increase of silica sol content, the discharge specific capacity of LiMn2O4) decreases and the capacity retention rate increases first and then decreases. When the amount of silica sol was less than 2.0 wt%, the capacity retention rate of the sample LiMn2O4 increased from 92.241% to 94.068%, but when the amount of silica sol was more than 2.0 wt%, the capacity retention rate of the sample began to decrease.
【学位授予单位】：齐鲁工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM912

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