Chemical Treatment of Carbon Nanotubes as Electrodes in Electrochemical Double-Layer Capacitors

Multi-walled carbon nanombes with homogeneous diameters （40 - 60 nm）, produced by chemical vapor deposition of hydrocarbon gas, are purified by nitric acids. Infrared and Raman studies indicate that oxygen containing surface groups, which are predominately carboxylic, phenolic and lactonic groups, are introduced into purified carbon nanotubes. Then three kinds of block-form porous tablets of carbon nanotubes are fabricated as electrodes in electrochemical double-layer capacitors. Using mounded mixture comprising carbon nanotubes and binder powders provides these tablets. Comparison of the effect of different processing on the structural performance of the capacitors is specifically investigated. Using chemically treated electrodes, electrochemical double-layer capacitors with a specific capacitance of about 33 F/g are obtained with 38 wt % H2SO4 as the electrolyte.

The key challenges and future opportunities of electrochemical capacitors

Electrochemical capacitors(ECs)with unique merits of fast charge/discharge rate and long cyclability are one of the representative electrochemical energy storage systems,possessing wide applications in power electronics and automotive transportation,etc.[1,2].Furthermore.

Carbon aerogels for electric double-layer capacitors

In this study, carbon aerogels were derived via the pyrolysis of resorcinol-formaldehyde (RF) aerogels, which were cost-effectively manufactured from RF wet gels by an ambient drying technique instead of conventional supercritical drying. By varying the R/C ratio (molar ratio of resorcinol to catalyst), mesoporous carbon aerogels with high specific surface area were prepared successfully and further investigated as electrode materials for electric double-layer capacitors (EDLCs). The textural properties of carbon aerogels obtained were characterized by nitrogen adsorption/desorption analysis and SEM. The electrochemical performances of carbon aerogels were investigated by impedance spectroscopy, galvanostatic charge/discharge and cyclic voltammetry methods. The results show that BET surface area and specific capacitance increase with R/C ratio, the maximum values of 727 m2·g-1 and 132 F·g-1 are achieved at R/C ratio will of 300. Increasing R/C ratio increase the average pore size of carbon aerogel electrode, which has improved the rate capability. Furthermore, EDLC with carbon aerogel electrodes has an excellent stability at large discharge current and long cycle life.

Influence of nitrogen hetero-substitution on the electrochemical performance of coal-based activated carbons measured in non-aqueous electrolyte

Nitrogen-containing carbons were prepared by modification of activated carbons.The modified carbons were used as electrode materials with improved electrochemical performance.Precursor anthracite was activated by KOH(KOH:anthracite= 1:1), modified by melamine or urea and then treated at 1173 K to obtain the modified carbons.The porous structure, the chemical composition and the electrochemical characteristics of the carbons were investigated by nitrogen sorption, XPS and electrochemical methods respectively.Electrochemical experiments were performed in an organic electrolytic solution of 1 M(C2H5)4NBF4/PC.The samples modified by the different methods showed differences in chemical composition that introduced varying degrees of electrochemical performance enhancement.The presence of nitrogen enhanced the electron donor properties and the surface wettability of the activated carbons:this ensured a sufficient utilization of the exposed surface for charge storage.

Effect of ball-milling technology on pore structure and electrochemical properties of activated carbon

The effects of particle size of activated carbon （AC） on its wettability, electrode coating technology and electric chemical performance were studied to assemble nonaqueous electric double layer capacitors （EDLCs） for high power requirements. The results show that the specific surface area and total pore volume of AC decrease from 2 137 m^2/g to 1 683 m^2/g, and 0.95 cm^3/g to 0.78 cm^3/g, respectively, if it is ball-milled for 8 h. The pore size distributions are similar in the range of 0.7 nm to 3.5 nm for different ball-milling time. There exists oxidation on the surface of AC during the ball-milling process and the ratios of O-C=O oxygen compositions increase whereas those of C-O, C=O decrease. The peeling strength of AC coated on current collector is almost inverse proportion with the particle size of AC as well as the resistance of EDLCs, and its capacitance decreases about 6%.

KOH添加方式对煤基活性泡沫炭电化学性能的影响

以强黏性炼焦煤为原料,经常压自发泡法制得的煤基泡沫炭(NCF)为碳基底,KOH为活化剂,采用机械混合、水溶液浸渍、乙醇浸渍三种不同的方式制备煤基活性泡沫炭(HPCs),并将其用作双电层电容器的电极材料,研究了KOH添加方式对其微观结构和电化学性能的影响。结果表明,KOH分散度和附着性对煤基活性泡沫炭孔隙结构的生成、晶体结构、表面化学性质以及电化学性能有显著影响。煤基泡沫炭本身具有三维连通泡孔结构,有利于活化剂(KOH)深入材料的泡孔内部并为其提供大量附着位点,增大活化剂与碳基体的接触面积进而发生高效的活化。KOH水溶液的流动性较好,可以使K+更有效地穿插在NCF的泡孔结构中,在活化过程中作用于缺陷部位,在碳基体内部基质上产生更多的微孔以及介孔结构,有效地放大了活化效果。KOH水溶液浸渍泡沫炭材料制得的ACF-W样品拥有最高的比表面积(3098.35 m^(2)/g)、总孔体积(1.68 cm^(3)/g)、介孔体积比(59.13%),将其用作电极材料表现出优异的比电容(310 F/g)以及循环稳定性。

EDLC charging performance for microgrid applications

In order to review storage performance of the electric double layer capacitor （EDLC） in microgrid applications, charging time and storage efficiency issues are mainly studied aiming at three different charging modes, including the constant voltage charging mode （CVCM）, the constant current charging mode （CCCM） and the constant power charging mode （CPCM）, based on the practical EDLC product. Numerical calculation methods are presented for different charging modes, and the charging efficiency is also reviewed with strict mathematical deductions, which is validated to be accurate enough and applicable through a simple case with the PV/EDLC system illustration. Finally, trade-off problems between charging time and energy loss are also studied. Research results show that the CPCM is more suitable for microgrid networks compared with the traditional constant-voltage and constant-current charging modes. The hybrid charging method is recommended to save energy and keep high efficiency relatively at the same time. However, how to manage the combination percentage of different charging modes in a reasonable way should be dealt with according to the practical requirements.

酚醛树脂基活性炭微球的电化学性能II.作为EDLC电极材料的活性炭微球的制备及电化学性能

用直流恒流循环法考察在不同的活化条件下得到的酚醛树脂活性炭微球作为双电层电容器电极的电化学性能。结果表明,要得到高比电容的电容器电极材料,水蒸气活化的最佳条件为:在800℃下活化1h,水蒸气的量控制为氮气量的40%。在此条件下得到的酚醛树脂活性炭微球作为电极具有良好的循环充放电性能,比电容可达到143F/g,充放电效率高达98%。在2.0nm^7.5nm之间的孔对活性炭微球的比电容影响显著。

EDLC用分级孔炭电极材料的制备与超电容性能研究

采用有机-有机自组装法和化学活化法相结合,制备了分级孔炭电极材料(HPC)。氮气静态吸附测试表明,化学活化使介孔炭的孔壁上产生了大量的微孔,从而使其比表面积大大增加。与以硬模板法制备的有序介孔炭(OMC)相比,HPC比OMC具有更为优异的电化学性能,这是因为微孔和介孔直接相连的分级孔结构,不仅增大了比表面积,而且能够显著减小电解质离子在电极材料孔道内的扩散阻力。

Carbon-Based Electrode Materials for Supercapacitor： Progress, Challenges and Prospective Solutions

Carbon-based materials are typical and commercially active electrode for supercapacitors due to their advantages such as low cost, good stability and easy availability. In the light of energy storage, supercapacitors mechanism is classified into EDLCs （electrochemical double layer capacitors） and pseudocapacitors. Multidimensional carbon nanomaterials （active carbon, carbon nanotube, graphene, etc.）, carbon-based composite and corresponding electrolyte are the critical and important factor in the eyes of researcher. In this minireview, we will discuss the storage mechanism and summarize recent developed novel carbon and carbon-based materials in supercapacitors. The techniques to design the novel nanostructure and high performance electrodematerials that facilitate charge transfer to achieve high energy and power densities will also be discussed.

添加不同生物质对无灰煤基活性炭结构及性能的影响

通过在无灰煤中添加不同生物质(玉米芯或松木屑),制备双电层电容器用活性炭电极材料,探究生物质对无灰煤基活性炭结构和电化学性能的影响。采用SEM、XRD、FTIR、N2吸脱附表征其结构和组成,通过循环伏安、恒流充放电及交流阻抗测试其电化学性能。从生物质组成成分来看,添加高纤维素含量的生物质更有利于中孔的发育,使活性炭的孔隙结构更加完善。高纤维素半纤维素含量能够有效降低碳材料的电荷转移电阻和物质扩散阻力,使离子在孔结构之间的传输更加迅速。向无灰煤中添加玉米芯时,比电容提升45%,电荷转移电阻降低65%;向无灰煤中添加松木屑,比电容提升30%,电荷转移电阻降低35%,证明添加高纤维素含量的生物质更有利于活性炭的结构完善和电化学性能提升。

Fabrication and Electrochemical Properties of Carbon Nanotube-based Composite Electrodes for Electrochemical Capacitor Applications

1 Results Electrochemical capacitors (ECs) are expected to be used in hybrid electric vehicles in combination with batteries or fuel cells because of their higher power density than batteries. ECs using electrical double layer capacitance of carbon based materials and pseudocapacitance of transition metal oxides are called electrochemical double layer capacitors (EDLC) and supercapacitors (or pseudocapacitor), respectively. Transition metal oxides are considered the best candidates for high energy dens...

电化学电容器的特点及应用

电化学电容器是一种介于电池和传统电容器的新型储能元件,具有比传统电容器更大的电容量,比电池更高的功率密度,更长的循环寿命,无需维护,引起了世界各国的广泛关注。综述了电化学电容器的原理、分类、特点以及国内外的发展状况。系统地介绍了电化学电容器的目前正在实用的领域以及正在开发新的使用领域。

新型能源器件——超级电容器研究发展最新动态

介绍了超级电容器工作原理、结构特点 ,并综述了国内外最新研究发展动态及产业化情况。超级电容器是近年来出现的一种新型能源器件 ,兼有常规电容器功率密度大、充电电池能量密度高的优点 ,可快速充放电 ,且寿命长 ,很有希望发展成为一种新型、高效、实用的能量储存装置。超级电容器的工作原理、结构特点与普通电容器有很大不同。超级电容器主要由极化电极、集电极、电解质、隔离膜、引线和封装材料几部分组成 ,各部分的组成、结构均对其性能有重要的影响。

电化学混合电容器

电化学混合电容器是一种介于超级电容器和电池之间的新型贮能元件。与传统的双电层电容器相比 ,它具有更高比容量和比能量 ,与电池相比 ,具有更高的功率密度和较低的能量密度。叙述了电化学混合电容器的原理、特点、最新研究进展 。

粘结剂对块状极板碳纳米管双电层电容器性能影响研究

碳纳米管具有良好的导电性和合适的双电层形成区，适于制作双电层电容器极板． 不同粘结剂的使用会影响电容器的性能，分别选用酚醛树脂和聚四氟乙烯（ＰＴＦＥ）作为碳纳米 管极板的粘结剂，在有机电解质溶液中，研究其电容性能与比表面积和极板结构的关系，从而 找出合适的碳纳米管极板粘结剂．

电化学电容器的设计

电化学电容器是一种介于传统电容器和电池之间的新型元器件,它比传统电容器具有更高比电容量和比能量,比电池具有更高的比功率,具有广泛的应用前景。详细介绍了电化学电容器的分类及设计过程,讨论了电化学电容器设计过程中注意的几个重要问题:结构单元的设计,电极的设计和制备,电极厚度和材料性能,等效串联电阻,电解质,隔膜,电压平衡,装配和封装。

以食糖热裂解碳作为电极的双电层电容器的性能

A new precusor of activated carbon material--sugar was pyrolyzed under many different conditions. Experiments were carried out to search for optimal pyrolyzing conditions. It was found that sugar should be carbonized at 700 ℃ and activated with potassium hydroxide at 800 ℃. The activated carbon prepared from pyrolytic treatment of sugar is therefore potential candidates as electrode material of electric double layer capacitor.

“超电容”电化学电容器研究进展

电化学电容是一种与电池和传统的电容都不同的新型储能器件。电化学电容具有比传统的物理电容高 2 0～ 2 0 0倍以上的质量比电容。研究证明 ,电化学电容所具有的大容量是由于电极表面的双电层电容和氧化还原反应导致的“准电容”的共同作用而引起的。一般利用前者储存能量的电容器被称为“双电层电容” ,后者被称为“超电容”。系统地介绍了电化学电容器的广泛应用、发展历史、储能机理 ,以及它与电池、传统物理电容的区别 ,并详细地综述了“超电容”电容器电极活性材料的最新研究进展。