摘要：本实验通过浮动催化热裂解法制备的碳包覆渗碳体纳米复合颗粒，经透射电子显微镜、X射线衍分析，700 ℃下制备样品为-氧化铁，其粒径为1〜5 nm碳壳平均厚度为〜1。2 nm；900 ℃下制备样品为渗碳体，颗粒的直径为5〜20 nm，碳壳平均厚度为〜2。0 nm；1100℃下制备样品为渗碳体，颗粒的直径为10〜30 nm，碳壳平均厚度为〜2。5 nm。通过循环伏安曲线法和恒电流充放电曲线，评估了碳包覆渗碳体纳米复合颗粒在锂电上的电化学表现，900 ℃制备样品电化学性能要远远高于700 ℃和1100 ℃，比容量在0。2 A g-1、0。5 A g-1、1A g-1、3A g-1四个电流密度下所对应的值分别为793 mAh g-1、674mAh g-1、692mAh g-1、586mAh g-1。700 ℃制备的样品由于制备时碳包覆性能不佳，发生氧化反应使得金属核心成分发生改变，导致其电化学性能比900 ℃制备样品要低，1100 ℃制备的样品由于制备温度升高导致其粒径和石墨壁厚变大，降低了锂离子存储的活性位以及电化学性能。综上所诉900 ℃制备的复合材料拥有着良好的倍率性能，其作为锂电负极有着优秀的应用前景。74106
毕业论文关键词：渗碳体；纳米材料；复合材料；锂电；比容量
Synthesis of cementite nanocomposite particles and its application in lithium battery
Abstract: Cementite nanoparticles encapsulated with graphitic shells were prepared from floating catalytic pyrolysis。According to transmission electron microscopy (TEM) and X ray diffraction (XRD) analysis, the sample prepared at 700 ℃was alpha iron oxide with the particle sizes of 1-5nm and carbon shell average thickness of ~1。2nm;the sample prepared at 900 ℃ was cementite with the particle sizes of 5-20 nm and carbon shell average thickness of ~2 nm;the sample prepared at 1100 ℃ was cementite with the particle sizes of 10-30 nm and carbon shell average thickness of ~2。5 nm。Electrochemical performance ofthe prepared samples were evaluated by cyclic voltammetry method and galvanostatic charge and discharge curves。 As a result, the performance of the Fe3C@Cprepared at 900 ℃is much higher than ones prepared at 700 or 1100 ℃。 At current densityof 0。2, 0。5, 1 and 3A g-1, their specific capacity was 793, 674, 692, 586 mAh g-1, respectively。The poor performance of samples prepared at 700 ℃ is due to their imperfectcarbon shellslead to oxidation of their ferrous cores。 Fe3C@Cprepared at 1100 ℃ has a bigger diameter and a thicker graphitic shell, which decreased its specific surface area and the activityposition for electrochemicalstorage of lithium ions。 Thus,Fe3C@Cprepared at 900 ℃ has very good rate capability, which is a promising anodematerial for lithium ion batteries。
Key words: Cementite; Nanomaterials; Composite; Lithium ion batteries; Specific capacity
目录
1 绪论 1
1。1 碳材料 1
1。1。1 碳的简介 1
1。1。2 C60的性质及应用 1
1。1。3 石墨烯的性质及应用 3
1。2 渗碳体 4
1。2。1 渗碳体的结构 4
1。2。2 渗碳体的电学性质 5
1。2。3 渗碳体常用的制备方法 5
1。3 锂离子电池 7
1。3。1 锂离子电池概述 7
1。3。2 锂离子电池发展 7
1。3。3 锂离子电池的工作原理 8
1。3。4 锂离子电池正极材料 渗碳体纳米复合颗粒合成及在锂电上的应用:http://www.youerw.com/cailiao/lunwen_84605.html