双电层电容器用多孔炭材料的研究与开发

本文阐述了双电层电容器的工作原理，探讨了多孔炭材料的比表面积、孔径分布、表面官能团、表面石墨微晶取向、体积密度和电导率以及电化学稳定性等微孔结构与物理化学性质对其电容特性的影响，介绍了近年来用作双电层电容器电极的几种新型多孔炭材料的研究进展。     

双电层电容器电极材料最新研究进展

对双电层电容器炭基电极材料中已经产业化的和颇具产业化前景的活性炭、碳纳米管、炭凝胶等几种材料进行了综述，分析了它们的性质、特点和研究进展。     

多孔淀粉基炭微球的制备及其在双电层电容器中的应用

通过简单的无机盐磷酸氢二铵催化稳定化、炭化及不同碱炭比KOH活化制备了高比表面积的多孔淀粉基炭微球材料。采用电子扫描显微镜（SEM）、高分辨透射电子显微镜（HRTEM）及N₂吸脱附测试对实验所制得的炭微球样品的形貌及孔结构进行了分析。结果表明：不同KOH碱炭比制备的多孔淀粉基炭微球材料具有较大的比表面积（﹥2 300 m²/g）,且均含有大量的大孔和微孔,在6 mol/L的 KOH电解液对称的双电层电容器中多孔淀粉炭材料表现出优异的电化学性能,在100 A/g的大电流密度下,炭微球电极材料具有最大的质量比电容高达248 F/g。     

低温脱除超级电容器用多孔炭含氧官能团

提升双电层超级电容器(EDLCs)能量密度的关键在于提高多孔炭电极材料的耐电压特性。然而目前提高多孔炭耐电压特性的难点是既脱除多孔炭的含氧基团、又不破坏多孔炭的层次孔结构。对此,选择镍基催化剂、利用催化剂表面发生的氢溢流现象,实现低温条件下脱除多孔炭的含氧基团,得到低氧含量的多孔炭。与H₂气氛下的热还原脱氧过程相比,基于氢溢流现象的脱氧过程除了热解反应和加氢反应,还包括高活性氢原子参与的剧烈加氢反应。此外,考察了基于一级氢溢流和二级氢溢流现象的多孔炭脱氧过程的作用机制。由于镍纳米颗粒和多孔炭之间存在Ni-O-C键和Ni-C键,一级氢溢流抑制了多孔炭含氧基团的脱除。二级氢溢流避免了Ni-C键和Ni-O-C键的形成,解离的高活性氢原子可在厘米级别的长距离范围内扩散,能更有效脱除多孔炭表面的C-O、CO等含氧基团。此外,二级氢溢流脱氧后得到的多孔炭(PC-Ni-655)的碳层结构的有序度提高且孔道结构没有被破坏。当PC-Ni-655应用于EDLCs时,在3.3 V的高电压窗口下表现出较小的自放电现象和良好的循环稳定性(在1 A·g^-1循环5 000圈后,容量保持率为87.9%)。     

超级电容器用生物质衍生多孔炭材料研究进展

能源消费增加促使绿色能源开发成为趋势,同时推动能源存储系统快速发展,超级电容器以高功率密度和长循环寿命的优势得到广泛关注,其中电容炭材料逐渐成为研究热点。用来源广泛、有可再生性、价格低廉、绿色环保的生物质制备超级电容器用多孔炭材料,在开发绿色能源的同时解决了能源存储问题。多孔炭材料结构调控与性能完善是提高超级电容器性能的重要途径之一。综述了生物质衍生多孔炭材料及其在超级电容器领域的应用,按原料来源(植物、动物和微生物)及材料维度(0D、1D、2D和3D)的分类体系,多孔炭材料制备方法及技术现状。将多孔炭的制备分为炭化和活化,简述了炭化与活化机理、活化方式选择和常见活化剂特性,但生物质衍生多孔炭材料制备过程中影响因素多,且性能不及传统煤基碳材料,需进行多方面设计优化,包括选择生物质前驱体、合理使用炭化技术、调控活化过程各影响因素和选择改性过程中掺杂物等。基于在超级电容器领域的应用需求,重点探讨生物质多孔炭材料优化方式,包括孔结构调控、表面元素掺杂及与石墨烯复合形成新型炭材料等。梳理多孔炭材料用于超级电容器中时的难题与重点,通过寻找多孔炭材料在高比表面积、均匀孔隙分布和高导电性3方面的最优...     

美研究人员利用石墨烯开发出柔性超级电容

<正>美国莱斯大学利用石墨烯等开发出了柔性双电层电容器(也叫超级电容器)。相关论文已发表在《ACS NANO》上。这种双电层电容器的特点是耐弯曲性出色。莱斯大学的研究人员James Tour利用激光照射聚酰亚胺薄膜,在其表面形成了20μm左右的与石墨烯片相连接的泡状材料,将这种材料用作双电层电容器的电极。电容密度为16.5 m F/cm2,毫不逊色于普通的双电层电容器产品。James Tour利用这种材料制造双电层电容器的关键点是提前在聚酰亚胺薄膜上添加了硼酸。这样,与未添加硼酸     

PF与PVB共混炭化制备双电层电容器用多孔炭材料的研究

以酚醛树脂(PF)为原料，聚乙烯醇缩丁醛(PVB)为成孔剂，采用聚合物共混炭化法制备双电层电容器用多孔炭材料。通过热重(TG)和差热(DTA)分析，初步探讨了单一PF、PVB和PF、与PVB的共混物在炭化过程中的热解行为。考察了炭化温度和PF／PVB质量比对所得多孔炭的收率、BET比表面积、孔径分布和比电容的影响，并进一步探讨了以这种多孔炭材料作电极的模拟双电层电容器的充放电特性。结果表明，共混聚合物中PF与PVB是不相容的，热解过程各自独立进行，但存在一定的协同作用。随着炭化温度的升高，所得多孔炭的收率下降，比表面积、总孔容积和比电容先增大后减小，在800℃时达到最大值。随着PF／PVB质量比的增加，所得多孔炭的收率增加，比表面积和总孔容减小，比电容也减小。聚合物的混合方式及状态也是影响多孔炭性能的因素之一。以比电容为26．3F／g的多孔炭作电极的模拟双电层电容器具有良好的充放电性能。     

高表面活性炭电极的制备及其在双电层电容器中的应用

综述了高表面活性炭电极的原料制备、电极成型及修饰技术的研究进展,论述了双电层电容器电化学性能的影响因素,提出了提高双电层电容器电化学性能的方法,主要包括修饰和改善高表面活性炭的微观结构、改进电极成型工艺技术和电极的预处理方式等.并建议根据实际应用过程中双电层电容器的等效电路和Gouy-Chapman-Stern(GCS)模型理论,计算出高表面活性炭电极表面上的电解质的分布形态,以此作为研究双电层电容器的微观结构和吸附储电机理的突破点,为高表面活性炭电极用于双电层电容器的进一步发展提供理论指导.     

铂炭催化脱除超级电容器用多孔炭含氧官能团

开发可耐受高于2.7 V电压的多孔炭电极材料是双电层超级电容器（EDLCs）实现高能量密度的重要途径之一。以粒径小于10 nm的超细铂炭催化剂（Pt/C）引发了氢溢流,强化了高活性氢原子的解离,进而更加有效地脱除了多孔炭表面的含氧基团。利用5% Pt/C （质量分数,下同）可将多孔碳表面的含氧量降低至2%（摩尔分数,下同）。研究发现,重复使用多次后的Pt/C催化剂仍保持优于热还原法的脱氧效率。Pt/C催化剂作用下氢溢流脱氧后所得多孔炭（PC-Pt5/C-600-1st）的石墨微晶结构的有序度提高且孔结构得到较好保持,其作为EDLCs的电极材料可在3.3 V的高电压窗口下展现出良好的循环稳定性,在1 A·g^-1的电流密度下循环8 000圈后,容量保持率为88.4%。可重复使用的特点有利于降低相关工艺过程的成本负担。     

真空浸渍法制备生物质炭/石墨烯复合电极及其充放电性能研究

生物质炭具有天然的分级多孔结构,是双电层电容器优良的电极材料,但是其电导率低限制了其应用。将具有良好导电性能的石墨烯与生物质炭做成复合材料,可提高超级电容器的性能。采用真空浸渍法将石墨烯负载到生物质炭的表面和孔隙中。石墨烯不仅提高了生物质炭的电导率,而且增加了比表面积。生物质炭/石墨烯复合电极在电流密度为0. 5 A/g时,比电容大小为159. 74 F/g,比未负载石墨烯的纯生物质炭电极提高了4倍多。充放电循环5 000次,性能无衰减,呈现出良好的稳定性。     

铸型炭化法制备多孔炭材料的研究进展

铸型炭化法开辟了多孔炭材料制备研究的一个全新领域,近年来已成为能够最有效控制多孔炭材料结构的方法。本文概述了传统方法制备多孔炭材料的不足,重点综述了以硅胶、黏土、沸石和中孔硅分子筛为铸型制备多孔炭材料的最新研究进展,展望了铸型炭的应用前景,最后指出了铸型炭化法在制备多孔炭领域尚待开展的研究工作。     

PAN基凝胶聚合物电解质双电层电容器

为了得到安全、无泄漏、微型、超薄型的双电层电容器,采用内聚合方法制得聚丙烯腈基凝胶聚合物电解质双电层电容器,电解质的增塑剂为碳酸丙烯酯和碳酸乙烯酯,支持电解质为高氯酸锂,电极材料分别为比表面积1000m2/g和2600m2/g的活性炭。采用交流阻抗、循环伏安、恒流充放电、循环寿命等测试方法对内聚合式凝胶聚合物电解质及其组成的双电层电容器的性能进行了测试。结果表明,此种方法制得的双电层电容器的内阻小,比容量较大,其中以比表面积2600m2/g活性炭为电极材料的电容器的双电极比容量达到47.41F/g。     

Coconut kernel-derived activated carbon as electrode material for electrical double-layer capacitors

Carbonization of milk-free coconut kernel pulp is carried out at low temperatures. The carbon samples are activated using KOH, and electrical double-layer capacitor (EDLC) properties are studied. Among the several samples prepared, activated carbon prepared at 600 °C has a large surface area (1,200 m² g^?1). There is a decrease in surface area with increasing temperature of preparation. Cyclic voltammetry and galvanostatic charge–discharge studies suggest that activated carbons derived from coconut kernel pulp are appropriate materials for EDLC studies in acidic, alkaline, and non-aqueous electrolytes. Specific capacitance of 173 F g^?1 is obtained in 1 M H₂SO₄ electrolyte for the activated carbon prepared at 600 °C. The supercapacitor properties of activated carbon sample prepared at 600 °C are superior to the samples prepared at higher temperatures.     

Comparison of Pore Structures of Cellulose-Based Activated Carbon Fibers and Their Applications for Electrode Materials

This study presents the first investigation of cellulose-based activated carbon fibers (RACFs) prepared as electrode materials for the electric double-layer capacitor (EDLC) in lieu of activated carbon, to determine its efficacy as a low-cost, environmentally friendly enhancement alternative to nanocarbon materials. The RACFs were prepared by steam activation and their textural properties were studied by Brunauer–Emmett–Teller and non-localized density functional theory equations with N₂/77K adsorption isotherms. The crystallite structure of the RACFs was observed by X-ray diffraction. The RACFs were applied as an electrode material for an EDLC and compared with commercial activated carbon (YP-50F). The electrochemical performance of the EDLC was analyzed using galvanostatic charge/discharge curves, cyclic voltammetry, and electrochemical impedance spectroscopy. The results show that the texture properties of the activated carbon fibers were influenced by the activation time. Crucially, the specific surface area, total pore volume, and mesopore volume ratio of the RACF with a 70-min activation time (RACF-70) were 2150 m²/g, 1.03 cm³/g and 31.1%, respectively. Further, electrochemical performance analysis found that the specific capacitance of RACF-70 increased from 82.6 to 103.6 F/g (at 2 mA/cm²). The overall high specific capacitance and low resistance of the RACFs were probably influenced by the pore structure that developed outstanding impedance properties. The results of this work demonstrate that RACFs have promising application value as performance enhancing EDLC electrode materials.     

Complex capacitance analysis on rate capability of electric-double layer capacitor (EDLC) electrodes of different thickness

The complex capacitance analysis is utilized to examine the thickness-dependent rate capability of electric double-layer capacitor (EDLC) electrodes. Based on the transmission line model, the theoretical imaginary capacitance is derived for porous carbon electrodes, where the resistance relevant to ion transport in pores of carbon particles (intra-particle pores) and within electrode layer (inter-particle pores) is assumed to be the major component for equivalent series resistance (ESR). The use of hexagonal mesoporous carbon (HMC) as the EDLC electrode material, which has a well-defined pore structure, allows us to estimate the number of intra-particle pores in the composite electrodes such that the two resistance components are separately analyzed as a function of electrode thickness. As the theoretical derivation suggests, the time constant for intra-particle pores is invariant against the electrode thickness, whereas the time constant for inter-particle pores becomes larger for thicker electrodes. The poorer rate capability observed in the thicker electrodes is thus ascribed to a larger time constant for inter-particle pores.     

Enhanced surface hydrophobisation for improved performance of carbon aerogel electrochemical capacitor

A more efficient surfactant vinyltrimethoxysilane (vtmos) than previously reported one, sodium oleate (OAS), has been employed to enhance surface hydrophobisation of carbon aerogel for electric double layer capacitor (EDLC) application. In comparison with attachment of hydrophobic moiety of OAS species to carbon surface grafting of vinyltrimethoxysilane functional group enhances more efficiently the hydrophobisation of carbon material and the affinity toward propylene carbonate (PC) solvent, and accordingly improves more considerably the wettability of carbon in PC-based electrolyte solution. The enhanced wettability facilitates more rapid electrolyte ions transport within micropores of the vtmos modified carbon aerogel, resulting in lower internal resistance and energy loss than OAS modified carbon capacitor, and also favors more surface area for EDL formation, resulting in higher specific capacitance and energy for vtmos modified carbon aerogel electrochemical capacitor. In addition, vtmos modified carbon material has shown comparable charge-discharge cycling stability to that obtained by the original carbon.     

Development of Lignin-Based Terpolyester Film and Its Application to Separator Material for Electric Double-Layer Capacitor

For new application of technical lignins as separator material for electric double-layer capacitor (EDLC), we tried first to prepare bipolyester film by melt-polycondensation of polyethylene glycol lignin (PEGL) and maleic anhydride. The EDLC assembled with this film, however, showed lower electrochemical performance than the reference EDLC with commercial cellulosic separator. Porous bipolyester film was then prepared and the resulting EDLC exhibited improved specific capacitance, but high intrinsic and charge transfer resistances. Non-porous terpolyester film was prepared next, using polyethylene glycol 500,000 to improve flexibility of the film, which might lower the resistances. This film was flexible enough and provided the resulting EDLC with superior electrochemical performance to the bipolyester film. EDLC with porous terpolyester film was finally prepared and showed the highest electrochemical performance, comparable to the reference EDLC. Porous morphology and flexibility were key factors to fabricate lignin-based self-standing film as separator material for high-performance EDLC.     

Decrease in equivalent series resistance of electric double-layer capacitor by addition of carbon nanotube into the activated carbon electrode

An electric double layer capacitor (EDLC) was fabricated with the addition of carbon nanotubes (CNTs) to the polarizable electrodes to act as a conducting material. This EDLC showed a low equivalent series resistance of 2.5 Ω. This value was lower than that of an EDLC fabricated with the addition of acetylene black, which is widely used in commercial EDLCs.     

碳气凝胶电极用于NaCl溶液电容性除盐的研究

碳气凝胶是一种新型多孔碳材料,具有比表面积大、电导率高的特点。本文通过常压干燥制备了碳气凝胶,研究测试了其结构特性,用N aCl溶液模拟海水,利用CD I原理,以碳气凝胶作电极进行了N aC l溶液的除盐实验。实验表明,决定碳气凝胶的除盐效果的主要因素为比表面积和电导率。在不同配比结构中,以R/C为1500、M值为30%的碳气凝胶电极的除盐效果最佳。利用双电层电容模型解释探讨了碳气凝胶电极的除盐机理。     

High power density electric double-layer capacitor based on a porous multi-walled carbon nanotube microsphere as a local electrolyte micro-reservoir

A high rate capability is a primary requirement for an electric double-layer capacitor (EDLC) in practical applications, which is mainly governed by the ionic diffusion rate. Construction of the electrode structure with proper paths for the rapid transport of ions is an efficient method to facilitate the diffusion of ions in the electrode. In this study, we prepared multi-walled carbon nanotube microspheres (MWNTMS) with a stable porous structure via the spray drying method. The MWNTMS act as a local electrolyte micro-reservoir and provide stable ion transport paths in the EDLC electrode, which will facilitate the access of the electrode to the electrolyte and accelerate the diffusion rate of the ions. Using only MWNTMS as active materials, an areal capacitance of 105 mF/cm² at 30 A/g is observed at an areal density of 7.2 mg/cm². When the MWNTMS are combined with reduced graphene oxides (rGO) to form an rGO-MWNTMS hybrid electrode with an areal density of 3.0 mg/cm², a high areal capacitance of 136 mF/cm² at 100 A/g is observed. This rGO-MWNTMS-based EDLC presents a high areal power density of 1540 mW/cm². These favorable results indicate that MWNTMS are promising materials for applications in high power supercapacitors.