新型活性炭材料在双电层电容器中的应用研究

以椰壳为原料,利用特定的物理 化学方法在一定条件下制得双电层电容器活性炭电极材料.实验表明,该活性炭经压制成型后制作的双电层电容器,具有大的比电容,文中同时研究了酸处理、二次活化以及电极冷压成型方法对电极性能的影响.     

基于金属氧化物的赝电容器

电极是电化学超级电容器的重要组成部分,电极材料是决定超级电容器性能的最重要因素。金属氧化物电极材料兼有双电层电容和准电容性质,其比电容远远大于活性炭材料表面的双电层电容,基于金属氧化物电极材料的超级电容器具有使用寿命长、维护简单等优点,是一种新型、高效、实用的能量存储装置,引起研究者的广泛兴趣。本文综述了基于金属氧化物电极材料的赝电容器的储能原理、类型和性能的研究现状,并展望了其发展前景。     

酚醛树脂热裂解碳为电极的双电层电容器的电化学特性

双电层电容器具有体积小、容量大和价格便宜等特点 ,以活性炭为电极的双电层电容器是具有高度可靠性的特殊电源 ,在许多便携式电子仪器和通讯设备上被用作备用电源 .特别是具有相对大容量的电容器已与标准的铅酸蓄电池组成混合体系 ,应用在电动车辆上 [1] .酚醛树脂经热裂解制备的聚并苯导电材料 PAS是制备双电层电容器电极的最佳材料之一 [2～ 10 ] ,它可以进行 p型和 n型掺杂 ,而且耐化学腐蚀、耐氧化和热稳定性好 .本文通过热裂解酚醛树脂来制备容量大、等效串联电阻小、不使用任何重金属、对环境无污染和不需长时间更换的双电层电容器…     

活性炭电极材料的表面改性和性能

以硝酸、双氧水、氨水三种化学试剂分别对活性炭进行表面改性, 用N2吸附法和FTIR表征炭材料改性前后孔结构和表面官能团的变化. 制备了以改性活性炭为电极材料, KOH溶液为电解质的模拟双电层电容器. 用恒流充放电、循环伏安、交流阻抗等方法考察了双电层电容器的电化学性能. 结果表明, 改性活性炭比表面积和平均孔径有所降低, 并且在炭材料表面引入了含氧或含氮官能团, 如—OH、>CO、—NH2等, 使炭材料的润湿性增强、电阻减小、电化学性能显著提高. 用65%硝酸改性后炭材料的比容量最高达到250 F·g-1, 比原样炭提高了72.4%; 实验电容器的漏电流急剧下降, 只有3-18 μA, 为原来电容器的漏电流(371 μA)的0.8%-4.9%.     

高能量密度和功率密度炭电极材料

以核桃壳为原料, 采用同步物理-化学活化法制备活性炭(AC). 用氮气吸附法和傅立叶红外光谱(FTIR), 对活性炭的孔结构和表面官能团进行了分析. 以活性炭为电极材料制备炭电极, 6 mol·L-1 KOH溶液为电解液组装成超级电容器, 利用恒电流充放电、循环伏安、交流阻抗等电化学测试方法研究其电化学性能及其与活性炭材料结构的关系. 结果表明, 实验电容器的内电阻、漏电流小, 循环充放电稳定性好, 容量保持率高; 活性炭的比电容随比表面积的增加而增大, 且与BET比表面积呈线性相关; 孔径在1.5-4 nm之间的孔表面有利于形成有效的双电层. 中等比表面积1197 m2·g-1炭样的比电容高达292 F·g-1, 80 mA充放电时, 电容器能量密度高达7.3 Wh·kg-1, 功率密度超过770 W·kg-1,峰值功率密度为5.1 W·g-1.     

碳纳米管的修饰及其在超级电容器中的应用

碳纳米管以其窄孔径分布、高有效比表面积、良好导电性能、良好力学性能、优良化学稳定性和良好热稳定性以及较低成本等优点,被认为是超级电容器的理想电极材料之一.本文结合碳材料具有的双电层电容和金属氧化物、导电聚合物具有的准法拉第电容,综述了碳纳米管的修饰处理技术及碳纳米管/金属氧化物、碳纳米管/导电聚合物复合材料、碳纳米管原位再生长技术的研究进展,指出碳纳米管的修饰能更好地改善其电化学性质,因此碳纳米管复合材料是超级电容器电极材料研究的一个重要发展方向.     

双电层电容器用新型无灰煤(HyperCoal)基活性炭的制备

以无灰煤(HyperCoal)为原料,KOH和CaCO3为活化剂制备了煤基活性炭,采用低温N2吸附法表征了活性炭的比表面积和孔结构,测定了活性炭用作双电层电容器(EDLC)电极材料的电化学性能。考察了炭化温度、活化温度、活化时间和活化剂对活性炭电容特性的影响。研究结果表明,比表面积和比电容随着炭化温度的升高而降低,活化温度过高或活化时间太长对比电容有不利影响。此外,CaCO3影响活化过程中孔的开发,显著降低所制备活性炭的比表面积和比电容。在炭化温度为500℃、活化温度为800℃、KOH与焦的质量比为4∶1和活化时间2 h下所得活性炭的比表面积和总孔容分别达到2 540 m2/g和1.65 cm3/g,该活性炭电极在0.5 mol/L TEABF4/PC电解液中的比电容达到最大值46.0 F/g。     

高容量超级电容器电极材料的设计与制备

超级电容器寿命长,安全性高,并可以实现快速充放电,是化学电源研究的热点之一。然而,超级电容器的能量密度较低限制了其更多的应用。因此,超级电容器领域的研究关注点在如何提高超级电容器的能量密度。其中,提高比容量是提高能量密度的一种有效途径。本文通过对电极材料和电解液的优化来研究制备得到高容量超级电容器的方法。电极材料的比表面积、孔道结构和导电性对其电化学性能有着直接的影响。一方面,通过优化电极材料的孔道结构和比表面积可以增加活性位点并提高电解液离子传导率,从而得到高比电容。另一方面,电极材料导电性的提高有利于提升其电子传导率从而得到较高的比容量。本文分别对碳材料和金属氧化物/氢氧化物的优化达到了增加双电层电容和赝电容的目的。不仅如此,还可以通过在电解液中增加氧化还原电对从而得到高比电容。这一方法为高容量超级电容器的制备提供了新的思路。     

超级电容器炭电极材料孔结构对其性能的影响

采用无瓶颈的系列酚醛树脂活性炭为电极材料，用氮吸附和恒流充、放电，以及交流阻抗法，研究孔径和孔表面积等孔结构对其性能的影响.结果表明，活性炭电极材料双电层电容与微孔(孔宽度< 2.0 nm)表面和外孔(孔宽度 >2.0 nm)表面都有关系，但主要取决于微孔表面双电层电容.微孔表面比电容为21.4 μF•cm－2，外孔表面比电容< 10 μF•cm－2.外孔表面比电容较低可能是由于空间电荷层的影响.微孔孔径较大的炭材料具有高比电容和良好的高倍率放电的特性.     

炭化温度对烟杆基活性炭孔结构及电化学性能的影响研究

以烟杆为原料, 氢氧化钾为活化剂, 通过调节炭化温度(500～800 ℃温度范围)在相同活化条件下制备了具有不同孔隙结构的活性炭材料. N₂吸附测试表明随着炭化温度降低, 活性炭的比表面积和总孔容先增大后减小, 中孔比表面积和平均孔径却一直增大. 其中600 ℃炭化样品经KOH活化后可制得比表面积为3333 m²•g^－1, 总孔容为2.47 cm³• g^－1, 中孔孔容达2.11 cm³•g^－1的高中孔率高比表面积活性炭材料. 采用直流充放电法、交流阻抗法和循环伏安法测定上述多孔炭为电极材料的双电层电容器的电化学性能, 结果表明: 炭化温度不同的烟杆基活性炭电极均表现出良好的功率特性, 充放电流增大50倍, 容量保持率均在80%左右, 其中TS-AC-600活性炭电极在有机电解液中1 mA•cm^－2充放电时, 比电容达到190 F•g^－1. 较高的中孔率和较大的平均孔径使得烟杆基活性炭电极具有良好的高倍率充放电性能.     

A novel carbon electrode material for highly improved EDLC performance

Porous materials, developed by grafting functional groups through chemical surface modification with a surfactant, represent an innovative concept in energy storage. This work reports, in detail, the first practical realization of a novel carbon electrode based on grafting of vinyltrimethoxysilane (vtmos) functional group for energy storage in electric double layer capacitor (EDLC). Surface modification with surfactant vtmos enhances the hydrophobisation of activated carbon and the affinity toward propylene carbonate (PC) solvent, which improves the wettability of activated carbon in the electrolyte solution based on PC solvent, resulting in not only a lower resistance to the transport of electrolyte ions within micropores of activated carbon but also more usable surface area for the formation of electric double layer, and accordingly, higher specific capacitance, energy density, and power capability available from the capacitor based on modified carbon. Especially, the effects from surface modification become superior at higher discharge rate, at which much better EDLC performance (i.e., much higher energy density and power capability) has been achieved by the modified carbon, suggesting that the modified carbon is a novel and very promising electrode material of EDLC for large current applications where both high energy density and power capability are required.     

Self-standing rationally functionalized graphene as high-performance electrode materials for supercapacitors

Supercapacitors（SCs） have attracted much attention as one of the alternative energy devices due to their high power performance,long cycle life,and low maintenance cost.Graphene is considered as an innovative and promising material due to its large theoretical specific surface area,high electrical conductivity,good mechanical properties and chemical stability.Herein,we report an effective strategy for elaborately constructing rationally functionalized self-standing graphene（SG） obtained from giant graphene oxide（GGO） paper followed by an ultrarapid thermal-processing.This treatment results in both the exfoliation of graphene sheets and the reduction of GGO by elimination of oxygencontaining groups.The as-prepared SG electrode materials without additive and conducting agent provide an excellent combination of the electrical double layer capacitor（EDLC） and pseudocapacitor（PC） functions and exhibit superior electrochemical performance,including high specific capacitance,good rate capability and excellent cycling stability when investigated in three-electrode electrochemical cells.     

Electric Double‐Layer Capacitor Based on an Ionic Clathrate Hydrate

Herein, we suggest a new approach to an electric double‐layer capacitor (EDLC) that is based on a proton‐conducting ionic clathrate hydrate (ICH). The ice‐like structures of clathrate hydrates, which are comprised of host water molecules and guest ions, make them suitable for applications in EDLC electrolytes, owing to their high proton conductivities and thermal stabilities. The carbon materials in the ICH Me₄NOH ? 5 H₂O show a high specific capacitance, reversible charge–discharge behavior, and a long cycle life. The ionic‐hydrate complex provides the following advantages in comparison with conventional aqueous and polymer electrolytes: 1) The ICH does not cause leakage problems under normal EDLC operating conditions. 2) The hydrate material can be utilized itself, without requiring any pre‐treatments or activation for proton conduction, thus shortening the preparation procedure of the EDLC. 3) The crystallization of the ICH makes it possible to tailor practical EDLC dimensions because of its fluidity as a liquid hydrate. 4) The hydrate solid electrolyte exhibits more‐favorable electrochemical stability than aqueous and polymer electrolytes. Therefore, ICH materials are expected to find practical applications in versatile energy devices that incorporate electrochemical systems.     

Highly porous electrodes from novel corn grains-based activated carbons for electrical double layer capacitors

In this study, novel corn grains-based activated carbons (CG-ACs) were prepared and their use as electrodes in the electrical double layer capacitor (EDLC) performed successfully. The structural properties, energetic heterogeneities and surface functional groups of CG-ACs were characterized using different techniques like nitrogen sorption data, adsorption energy distribution (AED) and X-ray photoelectric spectroscopy (XPS). The electrochemical properties of various CG-ACs were evaluated by using cyclic voltammetry. The maximum specific capacitance value as 257 F g⁻¹ was obtained in 6 M KOH electrolyte solution. The effects of various properties of the porous carbon materials on the EDLC performance were discussed.     

Transparent,flexible and solid-state supercapacitors based on room temperature ionic liquid gel

This paper describes a novel strategy to make fully transparent, solid-state and flexible supercapacitors based on room temperature ionic liquid (RTIL) gel and ITO electrodes coated on transparent polymer substrate without a separator, which enables the roll-to-roll technique for fabrication of such supercapacitors as printable devices. This is the first type of transparent electrochemical double layer capacitor (EDLC) based on ionic liquid gel.     

Metal-organic framework as a template for porous carbon synthesis

Porous carbon was synthesized by heating the precursor FA within the pores of MOF-5. The resultant carbon displayed a high specific surface area (BET, 2872 m2.g-1) and important hydrogen uptake (2.6 wt % at 760 Torr, -196 degrees C) as well as excellent electrochemical properties as an electrode material for electrochemical double-layered capacitor (EDLC).     

A review on the development of a porous carbon-based as modeling materials for electric double layer capacitors

Carbon electrodes are a key factor for electric double layer capacitors (EDLCs). Carbon gels have high porosity with a controllable pore structure by changing synthesis conditions and modifying preparation processing to improve the electrochemical performance of EDLCs. This review summarizes the preparation of carbon gels and their derivatives, the criteria to synthesize high surface area in each process, the development by some carbon forms, and EDLC applications. Porous carbons are also prepared as model materials by concentrating on how pore structure increases electrochemical capacitance, such as electronic and ion resistance, the tortuosity of pore channel, suitable micropore and mesopore sizes, and mesopore size distribution. This review emphasizes the significance of pore structures as the key factor to allow for the design of suitable pore structures that are suitable as the carbon electrode for EDLCs.     

酚醛基活性炭纤维孔结构及其电化学性能研究

利用水蒸汽活化法制备了酚醛基活性炭纤维(ACF-H2O), 对其比表面积、孔结构与在LiClO4/PC(聚碳酸丙烯酯)有机电解液中的电容性能之间的关系进行了探讨. 用N2(77 K)吸附法测定活性炭纤维的孔结构和比表面积, 用恒流充放电法和交流阻抗技术测量双电层电容器(EDLC)的电容量及内部阻抗. 研究表明, 在LiClO4/PC有机电解液中, ACF-H2O电极的可用孔径(d)应在0.7 nm以上. 随着活化时间的延长, ACF-H2O的孔容和比表面不断增大, 但微孔(0.7 nm ＜ d ＜ 2.0 nm)和中孔(d ＞ 2.0 nm)率变化很小, 活化过程中孔的延伸和拓宽同步进行, 但过度活化则造成孔壁塌陷, 孔容和比表面迅速下降. 因此, 除活化过度的样品外, 电容量随比表面积呈线性增长, 最高达到109. 6 F•g-1. 但中孔和微孔的孔表面对电容的贡献不同, 其单位面积电容分别为8.44 μF•cm-2和4.29 μF•cm-2, 中孔具有更高的表面利用率. ACF-H2O电极的电容量、阻抗特性和孔结构密切相关. 随着孔径的增大, 时间常数减小, 电解液离子更易于向孔内快速迁移, 阻抗降低, 电极具有更好的充放电倍率特性. 因此, 提高孔径和比表面积, 减少超微孔(d ＜ 0.7 nm), 是提高 EDLC能量密度和功率密度的重要途径. 然而仅采用水蒸汽活化, 只能在小中孔以下的孔径范围内进行调孔, ACF-H2O电极电容性能的提高受限.     

Surface Modification Effect and Electrochemical Performance of LiOH-High Surface Activated Carbon as a Cathode Material in EDLC

This study aimed to improve the performance of the activated carbon-based cathode by increasing the Li content and to analyze the effect of the combination of carbon and oxidizing agent. The crystal structure and chemical structure phase of Li-high surface area activated carbon material (Li-HSAC) was analyzed by X-ray diffraction (XRD) and Raman spectroscopy, the surface state and quantitative element by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) and the surface properties with pore-size distribution by Brunauer–Emmett–Teller (BET), Barrett–Joyner–Halenda (BJH) and t-plot methods. The specific surface area of the Li-YP80F is 1063.2 m²/g, micropore volume value is 0.511 cm³/g and mesopore volume is 0.143 cm³/g, and these all values are higher than other LiOH-treated carbon. The surface functional group was analyzed by a Boehm titration, and the higher number of acidic groups compared to the target facilitated the improved electrolyte permeability, reduced the interface resistance and increased the electrochemical properties of the cathode. The oxidizing agent of LiOH treated high surface area of activated carbon was used for the cathode material for EDLC (electric double layer capacitor) to determine its electrochemical properties and the as-prepared electrode retained excellent performance after 10 cycles and 100 cycles. The anodic and cathodic peak current value and peak segregation of Li-YP80F were better than those of the other two samples, due to the micropore-size and physical properties of the sample. The oxidation peak current value appeared at 0.0055 mA/cm² current density and the reduction peak value at –0.0014 mA/cm², when the Li-YP80F sample used to the Cu-foil surface. The redox peaks appeared at 0.0025 mA/cm² and –0.0009 mA/cm², in the case of using a Nickel foil, after 10 cycling test. The electrochemical stability of cathode materials was tested by 100 recycling tests. After 100 recycling tests, peak current drop decreased the peak profile became stable. The LiOH-treated high surface area of activated carbon had synergistically upgraded electrochemical activity and superior cycling stability that were demonstrated in EDLC.