氧化还原法制备石墨烯及其在锂离子电池中的应用

发布时间：2018-04-30 07:31

本文选题：石墨烯 + 还原氧化　；参考：《江苏大学》2017年硕士论文

【摘要】：石墨烯指从石墨上剥离下来的单层石墨片,仅一个原子厚度,是目前为止发现的最薄的二维纳米碳材料,它的最基本重复单元是有机化学中最为稳定的苯环结构。石墨烯拥有很多优异的特征,例如最薄最轻、高电导率和热导率、高载流子迁移率、自由的电子移动空间、高强度等,因此迅速崛起成为材料科学和凝聚态物理学领域的一颗新星,在纳米电子器件、催化剂、电池、电容器、光电子器件、新型复合材料以及传感材料等许多方面有着很好的应用前景。本论文中,运用了还原氧化法和液相剥离法成功的制备出了层数较少的石墨烯,并对制备的样品进行了傅里叶变换红外光谱(FTIR),扫描电镜(SEM),拉曼光谱(Raman),X射线衍射(XRD),原子力显微(AFM)测试表征。表征显示制备的还原氧化石墨烯样品为少层石墨烯,层数在4层以下;氧化石墨烯被氨水还原后,C=C键得到了修复,降低了石墨烯的缺陷程度。同时我们运用公认导电性相对比较好的液相剥离法制备了石墨烯对比样,用以评价我们制备出的氧化还原石墨烯在导电剂领域内的应用。液相剥离石墨烯样品表面非常光滑,部分呈现出薄片状且层数为3-6层,缺陷少,品质高。但是液相剥离石墨烯在实际应用中存在层数不均匀,难以满足工业化要求。在本论文中还将制备的两种石墨烯作为正极材料的导电剂应用到锂离子电池中,研究了其对锂离子电池性能的影响。在本研究中,配制锂离子电池正极浆料所用的粘结剂均为聚偏氟乙烯(PVDF);正极活性物质都统一采用磷酸亚铁锂(LFP);而导电剂则采用不同比例导电炭黑和石墨烯的复合材料,组装成的扣式电池在蓝电电池测试系统上进行测试。通过对比电池的充放电比容量、效率和充放电中压等性能可看出:电池的充放电比容量呈现出先增大后减少的趋势;而电池的充电中压和放电中压之间的差值则呈现出先减少后增大的趋势。因此,可得出随着导电剂中石墨烯添加量的增大,锂离子电池的性能呈现出先提高后下降的规律。此外,在导电剂中还原氧化石墨烯和液相剥离石墨烯添加量相同的情况下,添加液相剥离石墨烯组装的锂离子电池性能比添加还原氧化石墨烯的优良。最后,对充放电比容量、效率等性能最优的一组电池进行了充放电循环测试,结果显示电池的循环性能稳定良好。综上,可以看出石墨烯作为导电剂,添加在锂离子电池中能够较大的改善锂离子电池的性能。所以本论文将石墨烯作为一种导电材料,在提高锂电池性能方面的研究具有一定的借鉴意义。
[Abstract]:Graphene refers to a single layer of graphite strip stripped from graphite, with only one atomic thickness, which is the thinnest two-dimensional nano-carbon material found so far. Its most basic repeating unit is the most stable benzene ring structure in organic chemistry. Graphene has many excellent features, such as thinnest and lightest, high conductivity and thermal conductivity, high carrier mobility, free electron moving space, high intensity, etc. So it's a rising star in material science and condensed matter physics, in nanoscale electronic devices, catalysts, batteries, capacitors, optoelectronic devices, New composite materials and sensing materials have good application prospects. In this thesis, graphene with less layers was successfully prepared by reductive oxidation and liquid phase stripping. The samples were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Raman spectroscopy (Raman spectrum) and atomic force microscopy (AFM). The results showed that the reduced graphene was less than 4 layers, and the C bond was repaired after the reduction of graphene by ammonia, which reduced the defect degree of graphene. At the same time, we have prepared graphene contrast samples by liquid phase stripping method, which has relatively good electrical conductivity, to evaluate the application of redox graphene in the field of conductive agent. The surface of graphene in liquid phase is very smooth, some of them are flake, and the number of layers is 3-6, the defects are less and the quality is high. However, liquid phase exfoliation of graphene is difficult to meet the requirement of industrialization because of the uneven number of layers in practical application. In this thesis, two kinds of graphene were also used as cathode materials in lithium ion battery, and the effect of them on the performance of lithium ion battery was studied. In this study, the binders used in the preparation of positive paste for lithium-ion batteries were polyvinylidene fluoride (PVDF), lithium ferrous phosphate (LFPN), and conductive agents for different proportions of conductive carbon black and graphene composites. The assembled button battery is tested on the blue battery test system. By comparing the charge-discharge capacity, efficiency and mid-voltage of charge and discharge, it can be seen that the charge / discharge specific capacity of the battery increases first and then decreases; However, the difference between the middle voltage of charge and the middle voltage of discharge shows a tendency of decreasing first and then increasing. Therefore, with the increase of graphene content in the conductive agent, the performance of lithium-ion battery increases first and then decreases. In addition, when the amount of reduced graphene oxide and liquid phase exfoliated graphene is the same, the performance of lithium-ion battery assembled by adding liquid phase peeling graphene is better than that of adding reduced graphene oxide. Finally, a group of batteries with the best performance such as charge-discharge capacity and efficiency are tested, and the results show that the cycle performance of the battery is stable and good. It can be seen that graphene as a conductive agent can improve the performance of lithium-ion battery greatly. Therefore, graphene is regarded as a conductive material in this thesis, which has some reference significance in improving the performance of lithium battery.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ127.11;TM912

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