中国科学院新疆理化技术研究所机构知识库
Advanced  
XJIPC OpenIR  > 材料物理与化学研究室  > 学位论文
题名: 超级电容器用棉秆基多孔炭电极材料的研究
作者: 陈铭德
答辩日期: 2013-05-27
导师: 康雪雅 ; 吐尔迪.吾买尔
专业: 材料工程
授予单位: 中国科学院大学
授予地点: 北京
学位: 硕士
关键词: 棉秆基多孔炭 ; 超级电容器 ; 电极材料 ; 比容量 ; 复合材料
摘要:
超级电容器(Supercapacitors)是一种介于传统电容器与电池之间的新型储能元件。由于具有功率密度高、循环使用寿命长、能瞬间大电流充放 电、工作温度范围宽、安全、无污染等优点,在电动汽车、不间断电源、航空航天、军事等诸多领域均有广阔的应用前景。近年来,超级电容器引起了国内外研究者 的广泛关注,成为当前化学电源领域的研究热点之一。目前,商业化超级电容器电极材料主要集中于碳基材料,但炭电极材料存在着比容量偏低、孔径分布不均等问 题。因此,寻找新的碳源及活化技术,探索有效孔结构和表面性质的控制技术,研发炭复合材料,降低生产成本等对提高碳基超级电容器的性能具有重要意义。活性 炭材料由于具有比表面积大、化学稳定性好、孔径容易调控等优点,广泛用于超级电容器等储能器件。 本论文以新疆生物质资源棉花秸秆为原料,采用不同的活化方法制备高比表面积多孔炭及其复合材料,并研究了各种制备参数及工艺条件对棉秆基多孔炭材料的微观 组织结构和电化学性能的影响。研究成果主要体现在如下几个方面: (1)磷酸活化法制备超级电容器用棉秆基多孔炭电极材料的研究 以来源丰富、价格低廉、碳含量高、灰分低的新疆棉花秸秆作为原料,H3PO4为活化剂,采用化学活化法制备棉秆基多孔炭电极材料。运用热重分析、比表面测 试仪、SEM、XRD等手段表征了棉秆基多孔炭的表面形貌和结构。系统研究了活化剂磷酸溶液的质量分数、活化剂与棉秆的质量比(简称固液比)、活化温度及 活化时间等参数对棉秆基多孔炭的比表面积、孔径结构、表面形貌的影响。以制备的多孔炭为电极材料,1 mol L-1 Et4NBF4/AN 为电解液,组装成模拟纽扣式超级电容器。通过恒流充放电,循环伏安,交流阻抗测试。研究了不同的活化条件对材料材料电化学性能的影响。确定了棉秆基多孔炭 电极材料的最优制备条件。 (1)生物质原材料棉秆的活化过程包括三个阶段:第一阶段:(55-600℃),其重量损失很小,主要是样品中水分的蒸发;第二阶段 (600-800℃),样品的重量损失严重,主要原因是原材料的进一步裂解,同时伴随着CO、CO2、CH4、H2等气体的产生并释放,第三阶段,样品质 量损失小,主要是由于温度达到800℃时,样品的裂解反应已经完成,当温度达到800℃时,形成新的稳定的炭结构。活化温度、固液比、磷酸溶液的质量分数 及活化时间是影响棉秆基多孔炭电化学性能主要工艺参数。其比表面积随着随活化温度的升高、固液比的增大、活化时间的延长,呈先增大后减小的趋势。多孔炭的 孔径分布整体上向着孔径增大的方向移动。合理控制活化条件可得到一定的扩孔、提高其表面积的效果。当活化剂磷酸溶液质量分数为50%,活化温度为 800℃,棉秆与H3PO4的质量比(简称固液比)为1:4、活化时间为2 h时,制备出比表面积为1481 cm2 g-1,微孔孔容为0.0377 cm3 g-1,平均吸附孔径为2 nm的棉秆基多孔炭材料。将其组装成纽扣式超级电容器,通过恒流充放电,循环伏安和交流阻抗电化学测试,在2 A g?1的电流密度下,比电容量达到98 F g?1,且循环500次无容量衰减,表现出良好的电容特性。 (2)利用H3PO4活化法制备的棉秆基多孔炭为载体,与电解级MnO2进行复合,采用恒流充放电、循环伏安、交流阻抗测试,考察了MnO2混合量对其电 化学性能的影响。 研究表明,MnO2的不同比例的加入并未影响复合材料中棉秆基多孔炭材料的结构,而是对多孔炭的表面形貌有显著的影响,增加了活性物质和电解液的良好接 触,促进了电解质离子向电极材料表面运输。当MnO2负载量达到5%时,复合材料电容性能最优,它在2 A g?1的电流密度下,比容量达到160 F g?1。比复合之前容量提高39%,且循环500圈后,容量无衰减;该材料的循环伏安曲线呈现矩形状,无任何氧化还原峰,表明其电容量由双电层电容提供; 交流阻抗曲线中,复合材料(MnO2负载量为5%)的半圆弧最小,颗粒间电子传递阻力最小,低频区直线近似垂直与实轴,表现出良好的电化学电容特性。 (3)氢氧化钾梯度恒温活化法制备棉秆基多孔炭电极材料的研究 为了进一步提高棉秆基多孔炭电极材料的比容量,现将棉秆粉末在800℃进行炭化处理,然后将炭化产物与活化剂(5 mol L-1的KOH溶液)按照固液比1:4进行混合浸渍,待烘干后,将其在600-800℃温度区间进行梯度恒温活化,通过比表面积测试仪,SEM等测试手段 对材料的表面形貌及性质进行表征。通过KOH梯度恒温活化法可制备高比表面积及孔径发达的棉秆基多孔炭材料,当炭化温度为800℃,固液比为 1:4,600℃恒温1 h,700℃恒温1 h,800℃恒温2 h时,材料的比表面积达到1877 cm2 g-1,微孔孔容为0.0377 cm3 g-1,平均吸附孔径为2.85 nm,多孔炭呈现疏松的层状结构,这种层状状结构赋予了多孔炭较大的比表面积,有利于电解液的浸润、双电层的形成和比电容的提高。通过和直接活化法(炭化 温度为800℃,固液比为1:4,800℃恒温2 h)进行对比,发现梯度恒温活化法制备的多孔炭比表面积增长34%。将其组装成纽扣式超级电容器,进行恒流充放电、循环伏安、交流阻抗电化学性能测试,材 料表现出良好的电容特性,在2 A g?1的电流密度下,比容量能达到180 F g-1,而且循环500次,容量几乎无衰减。
英文摘要:
Supercapacitor is a new kind of storage device between conventional capacitor and battery, which was extensively studied due to their promising properties in terms of high power density, reversibly charged/discharged at higher rates, long cycle-life, wide working temperature, and environment-friendly have been applied widely in many fields that electric vehicle, uninterrupted power supply, aerospace, military affairs. Recently, supercapacitor is given more and more attention to the public, it has become one of the attractive research fields. Currently, the commercial supercapacitor electrode materials are focus on carbon materials, but they exist many prombles, such as low capacitance, non-uniform pore size distribution to be resolved. Tremendous efforts have been devoted to developing active electrode materials for supercapactance applications, searching new carbon resources, activation technology, controlling means of effective pore structure and surface activity, research and development of carbon composite materials, reduce production costs to improve the electrochemical performance. The acivated carbon is highly important and widely used in supercapacitor in its larger surface area, better chemical stability. Although there are many reports that using the cotton stalk to prepare high surface area of activated carbon material, the cost-effective porous carbons derived from cotton stalk is investigated as the active electrode material in supercapacitor for the first time. In this thesis, the porous carbon with high specific surface, carbon composite materials were prepared from the biomass resources of cotton stalk, by the process of different activation methods. The surface morphology of cotton stalk based porous carbon and structure characterization were analyzed by means of thermogravimetric analysis, nitrogen adsorption-desorption test, SEM, XRD. The influences of the activating temperature, activating time, the concentration of H3PO4, the ratio of H3PO4 to cotton stalk (solid-to-liquid ratio), specific surface area, pore structure and morphology of porous carbons derived from cotton stalk had been investigated. It was prepared as electrode material, all the measurements were carried in 1.0 mol?L-1 Et4NBF4/AN electrolyte. The effects of different activating parameters on galvanostatic charge-discharge performance, cyclic voltammetry and EIS of porous carbons electrode material. The optimal technologic conditions of preparing porous carbons based cotton stalk were established. (1)The cotton stalk from Xinjiang Province as raw material due to wide material source, low price, high fixed carbon content and low ash content. The whole pyrolysis process could be divided into three stages. The ?rst stage occurs between ambient temperature and 600 ?C and a minor weight loss observed is mainly due to H2O release by evaporation and the sample decomposed to uncondensable gas (CO, CO2, CH4, H2). The second stage is in the temperature range of 600-800 ?C and the strongest weight loss observed is attributed to the thermal decomposition of the raw material, these reactions are accompanied by further chemical transformations that include dehydration, degradation and condensation with a loss of aliphatic character and a corresponding increase in aromaticity and simultaneous release of gases. The third stage appears over a wide temperature range from 800 ?C to the ?nal temperature and a slight weight loss. It is indicated that the active sites on the carbons had reacted completely, and H3PO4 on the botanical structure through the penetration and dissolving of some components by breaking chemical bonds and it is followed by recombination to form a more thermally stable new polymeric and aromatic structures. So the activation temperature of 800 °C is more perfect than others for preparation of porous carbon from cotton stalk. Preparation of porous carbon from cotton stalk by H3PO4 activation method. The structure and performance of porous carbon are influenced mainly by the activating temperature, when the cotton stalk particles is 200 item, the mass ratio between cotton stalk and phosphoric acid solution(50%) for 1:4, activation time is 2 h and activation temperature at 800 °C, the porpous carbon have larger specific area(1481 cm2 g-1), microporous volume for 0.0377 cm3 g-1, and the average pore size of 2 nm. It has excellent electrochemical performance, The specific capacitance can be reached 114 F g-1, and without capacity fading after 500 cycles. (2)Manganese oxide/porous carbon composites were synthesized by H3PO4 activation. the improvements of porpous carbon modified by MnO2 were confirmed by the experiments of galvanostatic current charge/discharge, cyclic voltammograms(CV), alternating current impedance tests, respectively. The effect of different concentration of MnO2 on the electrochemical properties was investigated. It is indicated that different proportions of MnO2 did not affect the structure of the porpous carbon composite, and micrograph of the cotton stalk porpous carbon modified by MnO2 preparation conditions.When the mass ratio of MnO2 is 5%, the specific capacitance of composites electrode at 2 A g?1 is 160 F g?1, The composite capacity increased 39% than before. On the other hand, the specific capacitance without capacity fading after 500 cycles, the CV curve has rectangular shape between positive and negative at 50 mV s?1, and the prepared carbons show lower diffusion resistance in 1.0 mol L-1 Et4NBF4/AN electrolyte, the internal resistances was estimated to be 20 Ω for the carbon composites for 5% MnO2, It has excellent electrochemical characteristic. (3)Studying on preparation of porous carbon based cotton stalk electrode material by KOH- activation of gradient constant. In order to improve porpous carbon from cotton stalk electrode material specific capacity, preparation of porpous carbon based cotton stalk as electrode material by KOH-activation of gradient constant temperature for the first time in our laboratory. Firstly, the cotton stalk powder was carbonized at 800 °C, the carbon sample was impregnated with KOH solution (5 mol L?1) with a mass ration of 1:4, at activation temperature of 600 °C, 700 °C, 800 °C for 1 h, 1 h and 2 h, respectively. Significantly improved that the specific surface area and pore structure than the direct activation method in the experiment. The surface area of 1877 m2 g?1, total pore volume of 1.337 cm3 g?1, and especially the larger percentage of micropore (404 m2 g?1), It exhibits excellent electrochemical properties and the highest specific capacitances of 180 F g?1 in 1 mol L?1 in Et4NBF4/AN electrolyte at 1.0 A g?1and also displays high-rate long-cycle electrochemical performance even at a current density of 2 A g-1, the high specific capacitance of 180 F g?1. only 1.5% decrease of the specific capacitance is observed after 500 cycles at a discharge density of 2 A g?1. These results demonstrate that the porpous carbons derived from cotton stalk exhibit well cycle stability and very high degree of reversibility during repetitive charge-discharge cycles in organic electrolyte.
内容类型: 学位论文
URI标识: http://ir.xjipc.cas.cn/handle/365002/2485
Appears in Collections:材料物理与化学研究室_学位论文

Files in This Item:
File Name/ File Size Content Type Version Access License
陈铭德硕士论文.pdf(4585KB)学位论文--暂不开放View 联系获取全文

作者单位: 中国科学院新疆理化技术研究所

Recommended Citation:
陈铭德. 超级电容器用棉秆基多孔炭电极材料的研究[D]. 北京. 中国科学院大学. 2013.
Service
Recommend this item
Sava as my favorate item
Show this item's statistics
Export Endnote File
Google Scholar
Similar articles in Google Scholar
[陈铭德]'s Articles
CSDL cross search
Similar articles in CSDL Cross Search
[陈铭德]‘s Articles
Related Copyright Policies
Null
Social Bookmarking
Add to CiteULike Add to Connotea Add to Del.icio.us Add to Digg Add to Reddit
文件名: 陈铭德硕士论文.pdf
格式: Adobe PDF
所有评论 (0)
暂无评论
 
评注功能仅针对注册用户开放,请您登录
您对该条目有什么异议,请填写以下表单,管理员会尽快联系您。
内 容:
Email:  *
单位:
验证码:   刷新
您在IR的使用过程中有什么好的想法或者建议可以反馈给我们。
标 题:
 *
内 容:
Email:  *
验证码:   刷新

Items in IR are protected by copyright, with all rights reserved, unless otherwise indicated.

 

 

Valid XHTML 1.0!
Powered by CSpace