聂艳艳, 孙晓刚
, 蔡满园, 吴小勇, 刘珍红, 岳立福
南昌大学机电工程学院 南昌 330031
NIE Yanyan, SUN Xiaogang, CAI Manyuan, WU Xiaoyong, LIU Zhenhong, YUE Lifu
文献标识码: 分类号 O646 文章编号 1005-3093(2016)07-0538-07
通讯作者:
收稿日期: 2015-12-20
网络出版日期: 2016-07-25
版权声明: 2016 《材料研究学报》编辑部 《材料研究学报》编辑部
基金资助:
作者简介:
本文联系人: 孙晓刚, 教授
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摘要
用CVD法合成晶须状碳纳米管(WCNTs), 对其进行石墨化纯化处理。利用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线衍射(XRD)、拉曼光谱和热重分析(TGA)对其进行表征。以纤维素为基体材料, WCNTs为功能材料, 将分散好的WCNTs与纸纤维混合, 抽滤制成WCNTs复合纸, WCNTs复合纸的电导率由石墨化前14.1 S/m提升到石墨化后325.1 S/m。采用两电极体系, 以1 mol/L LiPF6为电解液, 通过循环伏安及恒流充放电方法来研究WCNTs复合纸为极片的超级电容器性能, 在扫描速率为1 mV/s时, 石墨化WCNTs复合纸电极的比容量达到90 F/g。在电流密度为800 mA/g时, 比能量和比功率分别为21.3 Wh/kg和2.1 kW/kg, 表现出良好的超级电容器性能。
关键词：
Abstract
Whisker-like carbon nanotubes (WCNTs) were produced by chemical vapor deposition (CVD) and then purified by graphitization at high temperature. The WCNTs were characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectra and thermogravimetric analysis (TGA). Water suspension consisted of WCNTs as functional material and cellulose fibers as matrix was prepared by speed-cutting procedure, and then WCNTs containing composite papers were prepared with the above suspension by vacuum filtration. The conductivity of the composite papers increased from 14.1 S/m to 325.1 S/m after incorporation of the graphitized WCNTs. A supercapacitor cell with two-electrodes was constructed with 1 mol/L LiPF6 as electrolyte. The electrochemical performance of supercapacitor was examined by cyclic voltammetry and galvanostatic charge/discharge. The results indicated that the supercapacitor has a maximum capacitance of 90 F/g by a scan rate of 1 mV / s. The specific energy and specific power reached 21.3 Wh/kg and 2.1 kW/kg respectively by a current density of 800 mA/g. These showed an excellent application prospect of the modified carbon nanotubes for supercapacitors.
Keywords：
超级电容器作为一种新型储能器件[1], 具有良好的环境友好性, 同时其具有寿命长, 污染小, 高的比功率, 近年来吸引了大批科学家的关注。碳纳米管自从1991年[2]被发现以来, 由于具有优异的力学性能[3, 4]、热学性能[5]、导电性能[6], 而成为科学家研究的热点。碳纳米管是理想的复合材料添加相[7, 8], 具有高达1000以上的长径比, 同时由于sp2轨道杂化形成大量离域π电子, 导电性能优异。但是实际生产过程中生产的碳纳米管都会残留一部分的催化剂杂质, 以及一些无定形碳, 这些杂质的存在限制了碳纳米管的使用, 目前碳纳米管的纯化方法主要是混酸[9, 10]和高温蒸发法[11], 混酸处理的同时去除了绝大多数的无定形碳及金属颗粒, 但处理过程繁琐, 污染严重, 同时也引入了一些官能团[12], 这些官能团的存在对碳纳米管的结构造成一定的破坏, 从而对性能会产生一定的影响。本实验采用的是对碳纳米管进行高温石墨化处理的方法来达到纯化的效果, 在石墨化的同时, 金属催化剂发生蒸发, 碳纳米管不会遭到破坏, 同时结晶度和导电性提高, 有望应用在超级电容器上。
随着科技的不断进步, 移动电子设备不断提出轻、薄、小的要求, 柔性储能器件便进入了人们的视线, 在柔性储能器件中碳纳米管[13-15]展现出了优异的特性。纸是一种很好的柔性基底材料, 来源广泛, 具有多孔的结构, 在电池领域具有很好的应用前景。Hu等[16]通过直接涂覆SWCNT分散液, 获得了高达200 F/g的比电容。Kang等[17]用碳纳米管和MnO2混合制备了一种柔性导电纸, 该导电纸的比容量达到540 F/g。本文采用原生纸浆为基体, 石墨化的WCNTs作为导电剂, 通过真空抽滤的方法制备WCNTs复合纸, 研究石墨化WCNTs复合纸的超级电容器性能。
WCNTs, 乙醇(C2H5OH, 纯度大于等于99.7%), 苯(C6H6, 纯度 99.99%), 二茂铁(C10H10Fe, 纯度大于等于95%), 噻吩(C4H4S, 纯度大于等于99%), 氢气(H2, 纯度99.99%), 氮气(N2, 纯度99.99%), 十二烷基硫酸钠(SDS), 蒸馏水。
超声清洗器KQ-3200(江苏昆山市超声仪有限公司); 鼓风干燥箱(北京市永光明医疗仪器厂); 行星式球磨机(长沙天创粉末技术有限公司); FM300实验室高剪切分散乳化机(上海弗鲁克公司); FA25实验室高剪切分散乳化机(上海弗鲁克公司); 上海辰华电化学工作站630E; 新威电池测试柜(CT-3008W-5V5A-S4); 电子天平 JA1003(天津市天马仪器厂); 扣式电池切片机 T-06(深圳市科晶智达有限公司)。
采用化学气相沉积法(CVD)制备WCNTs, 以二茂铁作为催化剂, 噻吩作为添加剂, 苯作为碳源, 按一定比例混合均匀, 将炉膛升温至1200℃, 升温期间不断通入N2, 将混合液与H2以一定速率喷入炉中, 待反应结束后, 取出生长的WCNTs。
WCNTs石墨化处理, 将生长的WCNTs放在石墨坩埚炉, 置于石墨化炉中, 对其进行抽真空。以10℃/min升温至2800℃, 保温24 h, 缓慢冷却, 取出石墨化的WCNTs。
适量WCNTs在行星式球磨机中以200 r/min球磨2 h, 称取球磨后的WCNTs 0.5 g, 分散剂(SDS)0.080 g, 蒸馏水100 mL, 适量的无水乙醇, 超声20 min, 然后在FA25高速剪切机上以10000 r/min剪切120 min, 制成WCNTs分散液。将原生木浆0.5 g(报纸、纸巾、书本等)加入到1000 mL蒸馏水中, 在高速剪切机上以3000 r/min剪切1 h制成纸浆悬浮液, 将WCNTs分散液与纸浆悬浮液混合, 在高速剪切机上以5000 r/min高速剪切1h, 抽滤制成WCNTs复合纸, 图1e, f为制作的柔性WCNTs复合纸, 纸直径150 mm, 厚度0.5 mm。放入真空鼓风干燥箱于100℃干燥12 h, 取出在切片机上切片, 极片在电子天平上称重, 在Ar保护气体手套箱中按电极、隔膜(Celgard2400 聚丙烯微孔膜)、电极的方式组装成纽扣电池。
采用配置了能谱仪(EDS)的环境扫描电子显微镜FEI Quanta 200 观察样品形貌; 多功能X-射线衍射仪XRD DI SYSTEM 表征样品相与相结构; 热重分析(TG/DTA, PYRIS DIAMOND); 拉曼光谱(Jobin Yvon, Labram-010); 表面电阻(数字式四探针测试仪St2258C); 电感耦合等离子体质谱仪(ICP—MS, RD001180)测试样品含铁量; 麦克ASAP2460物理吸附仪测试样品的比表面积; 电化学性能测试为CHI630E型电化学工作站两电极测试体系, 采用的电解液为1 mol/L LiPF6(溶剂碳酸乙烯酯(EC)和二甲基碳酸酯(DMC)质量比为1:1), WCNTs复合纸电极循环伏安曲线的电位窗口为0~2.5V, 扫描速率1~100 mV/s, 恒流充放电曲线的电流密度100~800 mA/g。
图1a为本实验制备的WCNTs, 该碳纳米管呈直线状, 管壁光滑, 缺陷少, 直径在50~80 nm之间, 具有易分散、结晶度高的特点。图1b所示为未石墨化处理的WCNTs的TEM照片。碳原子排列无序, 整体结构模糊且不规整, 这是由于WCNTs内部存在应力, 导致各层之间位错严重。图1(c, d)所示为WCNTs石墨化之后的TEM照片, WCNTs具有明晰的一维、中空管状结构, 但其内径较小, 仅有3~5 nm, 管壁较厚。可以看到碳原子按层规整排列, WCNTs呈现出明晰的层状内部结构, 并可以清晰观察到层与层之间的间隙(约为0.34 nm), 主要归因于石墨化的高温处理, 随着温度的升高, WCNTs内部的应力得到释放, 消除了各层之间的位错。
图1 WCNTs SEM像、石墨化处理前后WCNTs TEM像及WCNTs复合纸像
Fig.1 SEM image of WCNTs (a), TEM images of raw WCNTs (b), and graphitized WCNTs (c) (d), the photos of WCNTs composite paper (e) (f)
表1为两种WCNTs复合纸的电阻表征, 可以知, 石墨化和未石墨化WCNTs复合纸的表面电阻分别为6.2 Ω/sq、141.2 Ω/sq, 电导率依次为325.2 S/m、14.1 S/m。图2a, b为石墨化WCNTs复合纸的SEM照片, 以纸纤维为骨架, WCNTs缠缚在纸纤维上, 形成大量的孔状结构, 利用高速剪切的形式制备的WCNTs复合纸, WCNTs和纸纤维形成的是三维导电网络, 具有更好的导电特性, 这种结构更方便吸附更多的电解液, 增大活性物质与电解液的接触面, 从而具有更好的电池特性。
表1 石墨化与未石墨化WCNTs复合纸表面电阻和电导率
Table 1 Surface resistivity and conductivity of graphitized WCNTs and raw WCNTs composite paper
| Sample | Surface resistivity /Ωsq-1 | Conductivity /Sm-1 |
|---|---|---|
| Graphitized WCNTs paper | 6.2 | 325.2 |
| Raw WCNTs paper | 141.2 | 14.1 |
图2 石墨化WCNTs复合纸SEM像
Fig.2 SEM images of graphitized WCNTs composite paper at different magnifications: low magnification (a), high magnification (b)
图3a所示为WCNTs石墨化前后的XRD谱图。
图3 石墨化处理前后的WCNTs XRD和 Raman图谱
Fig.3 XRD (a), Raman (b) patterns of graphitized WCNTs and raw WCNTs
从图中可以看出, 石墨化处理前后, 样品的衍射峰均在2θ为26°处, 择优取向是(002)晶面, 但是石墨化处理后的WCNTs的衍射峰变窄, 说明较不经石墨化处理的WCNTs, 石墨化高温处理后的WCNTs内部的碳原子排列更加有序规整, 结晶度提高, 这有利于材料的导电性, 与TEM(图1)测试结果一致。图3b为WCNTs石墨化前后的拉曼图谱, WCNTs有两个明显的峰, 分别对应于1348cm-1 D带和约1586cm-1G带, D带峰与无定形碳的散射密切相关, 是由碳纳米管的无序性造成的, 而G带的振动与二维(平面)六角形晶格的sp2成键原子有关, 通常用G带与D带的强度之比(IG/ID)来评价碳材料的石墨化程度。石墨化以后G带峰变高变窄, 同时G带峰与D带峰的比值变大, 说明石墨化后WCNTs具有高的石墨化程度, 另外, 在2750cm-1处观察到一个尖锐的2D带峰, 进一步说明样品的结晶度高。
图4为非石墨化和石墨化WCNTs EDS谱图。
图4 石墨化处理前后WCNTs EDS图谱
Fig.4 EDS images of raw WCNTs (a) and graphitized WCNTs (b)
在非石墨化图谱中, 出现了C、Fe和O峰, 证明了含铁氧化物的存在, 石墨化以后只出现了C峰和O峰, 说明去除了含铁氧化物杂质。
图5a所示为未经石墨化处理的WCNTs的TGA图。图中蓝色线为WCNTs的失重曲线, 黑色线为失重速率。可以看出, 在500℃之前, WCNTs失重很少, 仅为0.1%, 主要是生产中产生的少量无定形碳, 从550℃开始失重急速加剧, 直到700℃时才出现稳定的平台, 直到800℃平台依然存在且未发生改变。不能烧蚀的这13.0%即为WCNTs的杂质, 主要为铁的氧化物, 还可能包含一些未知的异质。图5b所示为石墨化处理后WCNTs的TGA图, 可以看出, 经过石墨化处理的WCNTs, 在700℃开始出现较大的失重, 相对于未石墨化WCNTs, 说明具有更强的抗氧化能力, 更好的热稳定性。850℃以后, 杂质含量几乎为零, 经等离子体质谱仪检测含Fe量为20 mg/kg, 纯度接近100%(质量分数)。
图5 石墨化处理前后WCNTs TGA图谱
Fig.5 TGA images of raw WCNTs (a) and graphitized WCNTs (b)
图6a, b分别为未石墨化与石墨化WCNTs复合纸电极的循环伏安曲线, 电压窗口为0~2.5 V, 曲线的扫描速率分别为1 mV/s, 5 mV/ s, 10 mV/s, 30 mV/s, 50 mV/s, 100 mV/s。图6a在0.5 V以下出现了一个还原峰, 该峰的出现表明发生了Li+嵌入, 说明存在锂离子和双电层两种特性。由于非石墨化WCNTs含有更多的非晶结构, 所以嵌入的电位更高, 在1.5 V出现的峰代表Fe0被氧化成Fe3+的过程, 该峰随着扫描速率增加, 出现较大偏移, 存在较大的不可逆特性。图6b在0.5 V以下出现的峰为Li+在碳纳米管的嵌入峰, 由于经过石墨化处理, 碳纳米管的结晶度提高, 嵌入电位更低。随着扫描速率的增加Li+嵌入的更少, 所以电压越低, 因而出现峰值向左偏移。图6c为非石墨化与石墨化WCNTs复合纸电极比电容, 单电极的比容量可以通过公式算得:
其中U1和U2是扫描的起始电压和截止电压, i(U)是电流,
图6 石墨化处理前后WCNTs复合纸电极循环伏安曲线和不同扫描速率比容量对比
Fig.6 Cyclic voltammetry curves of raw WCNTs (a), and graphitized WCNTs (b) composite paper electrodes, Specific capacitance versus scan rate for raw WCNTs and graphitized WCNTs composite paper electrodes (c)
图7a, b分别为非石墨化与石墨化WCNTs复合纸电极恒流充放电曲线, 电流密度分别为100 mA/g、200 mA/g、400 mA/g 、800 mA/g, 图7a中显示充放电曲线三角形非常明显, 表现出良好的循环性能以及优良的双电层特性。由图7b可知, WCNTs经过石墨化处理, 结晶度提高, 导电性提升, 电子运动更好, WCNTs复合纸电导率由石墨化前14.1 S/m到石墨化后的325.1 S/m, 具有更长的放电时间。电容器的比电容可以通过充放电曲线得到, 公式为
其中I代表放电电流, m为单个极片活性物质质量, dV/dt是除去IR降的放电曲线的斜率。图7c为非石墨化与石墨化WCNTs复合纸电极在不同电流密度下比容量的对比, 可以发现, 石墨化WCNTs复合纸电极可以经受住更高的电流密度, 在800 mA/g时, 比容量还可以保留在24 F/g, 而未石墨化处理的WCNTs复合纸电极比容量为11.4 F/g, 同时与文献中报道[18]的在有机电解液中, 电流密度为100 mA/g时, 比容量为18 F/g, 石墨化的WCNTs复合纸电极比容量有提升。
图7 石墨化前后WCNTs复合纸电极恒流充放电和不同电流密度下比容量对比
Fig.7 Galvanostatic charge/discharge curves of raw WCNTs (a), and graphitized WCNTs (b) composite paper electrodes, specific capacitance versus current density for raw WCNTs and graphitized WCNTs composite paper electrodes (c)
图8为非石墨化与石墨化WCNTs复合纸电极比能量和比功率图, 其计算公式为
其中Csp表示比电容根据恒流充放电曲线计算得到, V表示充电电压, t表示放电时间, 在电流密度为800 mA/g时, 石墨化的WCNTs复合纸电极比能量达到21.3 Wh/kg, 比功率为2.1 kW/kg。
图8 石墨化处理前后WCNTs复合纸电极比能量与比功率
Fig.8 Ragone plot for raw WCNTs and graphitized WCNTs composite paper electrodes at different current density from 100 mA/g to 800 mA/g
1. 通过CVD法合成WCNTs, 该碳纳米管呈直线状, 经石墨化处理后, 碳纳米管的结晶度提高, 去除了金属催化剂颗粒以及无定形碳, 达到了纯化的效果, 碳纳米管的导电性增强, 但碳纳米管的比表面积减少。
2. 在扫描速率为1 mV/s时, WCNTs复合纸电极的比容量达到90 F/g, 同时经石墨化处理, WCNTs复合纸电极经受得住更高的电流密度, 在电流密度为800 mA/g时, 比电容保持在24 F/g, 比能量和比功率分别是21.3 Wh/kg和2.1 kW/kg, 电容器表现出良好的性能。
The authors have declared that no competing interests exist.
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Progress in research on carbon nanotube reinforced metal matrix composites, J .碳纳米管增强金属基复合材料的研究进展,
碳纳米管增强金属基复合材料由于高的比强度、比模量以及优异的热、电性能在航空航天领域具有很好的应用潜力,本文在分析大量文献的基础上,评述该类材料的制备技术和界面研究进展,对其典型性能进行归纳,指出碳纳米管的分散技术以及碳管、基体之间的界面特性应该是今后本领域的重点研究方向。
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| [8] |
Progress in research on carbon nanotubes microware absorbers, J .碳纳米管吸波材料研究进展,
介绍了碳纳米管的结构和性能特点,归纳和分析了碳纳米管吸波材料的最新进展,并提出了现有研究中存在的不足及进一步研究的方向。目前碳纳米管吸波材料的研究主要集中在不同结构碳纳米管吸波材料、磁性金属/碳纳米管复合吸波材料、稀土/碳纳米管复合吸波材料、铁氧体/碳纳米管复合吸波材料、聚合物/碳纳米管复合吸波材料以及陶瓷/碳纳米管复合吸波材料。对碳纳米管进行形貌控制、结构优化、表面修饰、复合掺杂改性以及界面结合和耐温性能的强化,是碳纳米管吸波材料今后的发展方向。
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| [9] |
Purification of carbon nanotubes,
<h2 class="secHeading" id="section_abstract">Abstract</h2><p id="">It is predicted theoretically and understood experimentally that carbon nanotubes (CNTs) possess excellent physical and chemical properties and have wide-range potential applications. However, only some of these properties and applications have been verified or realized. To a great extent, this situation can be ascribed to the difficulties in getting high-purity CNTs. Because as-prepared CNTs are usually accompanied by carbonaceous or metallic impurities, purification is an essential issue to be addressed. Considerable progress in the purification of CNTs has been made and a number of purification methods including chemical oxidation, physical separation, and combinations of chemical and physical techniques have been developed for obtaining CNTs with desired purity. Here we present an up-to-date overview on the purification of CNTs with focus on the principles, the advantages and limitations of different processes. The effects of purification on the structure of CNTs are discussed, and finally the main challenges and developing trends on this subject are considered. This review aims to provide guidance and to stimulate innovative thoughts on the purification of CNTs.</p>
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| [10] |
Purification of carbon nanotubes grown by thermal CVD, |
| [11] |
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| [12] |
Chemical oxidation of multiwalled carbon nanotubes,
<h2 class="secHeading" id="section_abstract">Abstract</h2><p id="">The effect of oxidation on the structural integrity of multiwalled carbon nanotubes through acidic (nitric acid and a mixture of sulfuric acid and hydrogen peroxide) and basic (ammonium hydroxide/hydrogen peroxide) agents has been studied. In order to purify the as-received material, a non-oxidative treatment (with hydrochloric acid) was also applied. Electron microscopy and thermogravimetric analysis clearly revealed that the nitric acid-treated material under reflux conditions suffered the highest degree of degradation, such as, nanotube shortening and additional defect generation in the graphitic network. Basic oxidative treatment led to the complete removal of amorphous carbon and metal oxide impurities but the structural integrity was found to be intact. X-ray photoelectron spectroscopy was employed to confirm the different functionalities produced for each oxidation agent, whereas titration measurements determined the relative concentration of carboxylic functions onto the graphitic surface. Moreover, a general relationship between the chemical treatment and the amount of non-graphitic carbon was established by means of Raman spectroscopy measurements. The possibility of controlling the required amount of functionality, carboxylic and hydroxyl, via these oxidation procedures is discussed.</p>
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| [13] |
De Volder, S. H. Tawfick, R. H. Baughman, R. H. Baughman, A. J. Hart, Carbon nanotubes: present and future commercial applications, |
| [14] |
All-solid-state flexible supercapacitors based on papers coated with carbon nanotubes and ionic-liquid-based gel electrolytes,
All-solid-state flexible supercapacitors were fabricated using carbon nanotubes (CNTs), regular office papers, and ionic-liquid-based gel electrolytes. Flexible electrodes were made by coating CNTs on office papers by a drop-dry method. The gel electrolyte was prepared by mixing fumed silica nanopowders with ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][NTf(2)]). This supercapacitor showed high power and energy performance as a solid-state flexible supercapacitor. The specific capacitance of the CNT electrodes was 135 F g(-1) at a current density of 2 A g(-1), when considering the mass of active materials only. The maximum power and energy density of the supercapacitors were 164 kW kg(-1) and 41 Wh kg(-1), respectively. Interestingly, the solid-state supercapacitor with the gel electrolyte showed comparable performance to the supercapacitors with ionic-liquid electrolyte. Moreover, the supercapacitor showed excellent stability and flexibility. The CNT/paper- and gel-based supercapacitors may hold great potential for low-cost and high-performance flexible energy storage applications.
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| [15] |
Flexible solid-state paper based carbon nanotube supercapacitor ,
This paper presents a flexible solid-state supercapacitor of high energy density. The electrodes of the supercapacitor are made of porous and absorbent cotton paper coated with single-wall carbon nanotubes. To ensure all solid-state configuration, a solid-state polymer-based electrolyte (poly (vinyl alcohol)/phosphoric acid) is used. The as-fabricated supercapacitor can be charged to over 365V. It has high specific capacitance and high energy density of 115.830165F/g carbon and 48.858765Wh/kg carbon. Its performance is comparable to that of commercial supercapacitors, which need to utilize liquid electrolytes. Flexible solid-state supercapacitors offer several significant advantages for use in hybrid electric vehicles.
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| [16] |
Highly conductive paper for energy-storage devices,
Paper, invented more than 2,000 years ago and widely used today in our everyday lives, is explored in this study as a platform for energy-storage devices by integration with 1D nanomaterials. Here, we show that commercially available paper can be made highly conductive with a sheet resistance as low as 1 ohm per square (Omega/sq) by using simple solution processes to achieve conformal coating of single-walled carbon nanotube (CNT) and silver nanowire films. Compared with plastics, paper substrates can dramatically improve film adhesion, greatly simplify the coating process, and significantly lower the cost. Supercapacitors based on CNT-conductive paper show excellent performance. When only CNT mass is considered, a specific capacitance of 200 F/g, a specific energy of 30-47 Watt-hour/kilogram (Wh/kg), a specific power of 200,000 W/kg, and a stable cycling life over 40,000 cycles are achieved. These values are much better than those of devices on other flat substrates, such as plastics. Even in a case in which the weight of all of the dead components is considered, a specific energy of 7.5 Wh/kg is achieved. In addition, this conductive paper can be used as an excellent lightweight current collector in lithium-ion batteries to replace the existing metallic counterparts. This work suggests that our conductive paper can be a highly scalable and low-cost solution for high-performance energy storage devices.
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| [17] |
Fabrication and characterization of flexible and high capacitance supercapacitors based on MnO2/CNT/papers ,
ABSTRACT Flexible paper-based supercapacitors were fabricated using carbon nanotubes (CNTs) and manganese oxides (MnO2), and their electrochemical properties were characterized in a three-electrode system. CNTs were synthesized via water-assisted chemical vapor deposition (CVD) and dispersed in water using the surfactant sodium dodecylbenzenesulfonate (SDBS). The solution containing dispersed CNTs was simply coated on papers by drop-dry method. MnO2 was then electrochemically deposited on the CNT-coated papers. The MnO2/CNT/paper supercapacitors showed high specific capacitance of 540F/g. Specific energy and specific power were 20Wh/kg and 1.5kW/kg, respectively, at current density of 5A/g in 0.1M sodium sulfate (Na2SO4) aqueous solution. Demonstrated high capacitance of the paper-based electrochemical capacitor makes it a promising candidate for flexible and low-cost energy storage device applications.
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| [18] |
Preparation of activated carbon nanotubes and their elrctrochemical capacitive performance in organic electrolyte, Acta Chim. Sin., 65(21), 活性碳纳米管的制备及其在有机电解液中的电容性能研究,
<p>以KOH为活化剂对碳纳米管进行化学活化制备双电层电容器用高比表面积活性碳纳米管. 采用TEM和N<sub>2</sub>吸附法表征活性碳纳米管的结构, 采用恒流充放电、循环伏安、交流阻抗等评价其在1 mol•L<sup>－1</sup> Et<sub>4</sub>NBF<sub>4</sub>/PC中的电容性能. 随活化剂用量增大、活化温度升高和活化时间的延长, 活性碳纳米管的比表面积和比电容都呈增大的趋势. 活化剂用量为3∶1, 800 ℃活化4 h制备的活性碳纳米管的比表面积663 m<sup>2</sup>•g<sup>－1</sup>, 比活化前提高了3倍, 其比电容达57.2 F• g<sup>－1</sup>, 比活化前提高了2倍. 将活性碳纳米管的比电容与其比表面积相关联, 发现两者之间具有非常好的线性关系, 并分析了原因.</p>
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