新碳源制备活性炭和石墨烯及其非等电极电容水系超级电容器（英文）

碳材料具有不同的微米和纳米结构以及本体和表面的官能基团,因此成为最普遍采用的超级电容器电极材料。典型的例子是活性炭和石墨烯。最近的研究趋势是通过新方法,以传统和新碳源,例如生物质、聚合物、氧化石墨、碳氢以及二氧化碳气体,来制备成本低、电容性能高的活性炭和石墨烯。特别是,大多数新碳源衍生碳非常适用于水系电解液。电荷存储不仅发生在"碳|电解液"界面上(形成双电层),也依靠本体和表面的官能化带来的氧化还原活性,包括有限离域价电子转移反应。此外,进一步理解电荷存储机制有助于设计出比传统对称电容器具有更高电压和比能量的非等电极电容水系超级电容器。本文综述了新碳源衍生碳材料和器件的最新进展,为超级电容器技术的持续发展助力。     

高比能超级电容器的研究进展

与传统蓄电池相比,超级电容器具有高功率密度、长循环寿命和使用温度范围宽等优势,但其能量密度较低.本文对超级电容器的结构、分类以及发展状况进行了简要介绍,重点阐述了本实验室近年来在研制高性能超级电容器方面的相关工作.主要从两个方面来提高超级电容器的能量密度:(1)通过采用中性水系电解液、有机电解液和离子液体提高对称型碳基超级电容器的电压窗口;(2)应用非对称型超级电容器,即一个电极采用具有法拉第赝电容电极材料或电池电极材料,而另一个电极则采用具有双电层电容的电极材料.同时介绍了由锂离子电池电极材料/活性炭作为正极,石墨作为负极组成的锂离子混合型超级电容器.最后,对超级电容器的发展方向进行了展望.     

润湿特性对超级电容器储能动力学的影响机理

润湿特性对超级电容器储能性能有着至关重要的影响。借助分子动力学模拟,本文研究了润湿特性对超级电容器储能动力学行为的影响。以石墨烯和晶体铜作为疏电解液和亲电解液电极材料。结果表明,在充电过程中,亲电解液铜电极呈现出非对称的U型微分电容曲线,负极电容是正极的～5.77倍,不同于经典双电层理论Gouy-Chapman-Stern(对称U型)和疏电解液型。该现象与离子自由能阻力分布密切相关,负极自由能阻力远小于正极(～2倍)和疏电解液电极,进而有利于强化双电层结构对电极电压的响应能力,导致更高微分电容。通过微分离子电荷密度,本文再现了微分电容演变规律,并发现改善润湿性会显著降低双电层厚度。最后,我们指出润湿性直接影响储能微观机理,将电荷储存机制从离子吸附和交换共同主导(疏电解液)转变到离子吸附主导(亲电解液)。本文所得结论揭示了润湿特性对储能动力学行为影响的原子层级机理,对超级电容器材料设计、构筑与润湿特性调控具有重要指导意义。     

镁热还原CO2气体制备介孔石墨烯及其电容特性研究

以CO_2为原料,采用金属镁热还原法,制备出富含介孔结构的石墨烯材料。分别利用X射线衍射、扫描电镜、透射电镜、拉曼光谱和N_2吸附-脱附等测试手段对材料的微观结构进行了表征。通过在镁粉中加入不同质量的MgO,可以实现对石墨烯形貌和孔结构的调控,当MgO/Mg质量比为8∶1时,产物(MRG-8)具有均一的介孔结构(4nm)。并对材料的电化学性能进行了测试,在1mol/L KOH的电解液中,MRG-8具有最高的比电容(171F/g),同时具有非常好的倍率特性,循环测试12000周,比电容保持率为94%。当采用[EMIM][BF4]离子液体作为电解液,以MRG-8为电极材料组装成的对称型超级电容器显示出超高功率密度(175k W/kg),对应的能量密度为28.1Wh/kg。因此,采用此方法制备的介孔石墨烯材料在高功率的超级电容器领域具有潜在的应用前景。     

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。     

碳凝胶/泡沫镍一体化电极用于高性能的超级电容器

以氧化石墨、间苯二酚、甲醛和泡沫镍为原料,经85 oC水热碳化处理,在泡沫镍表面原位聚合形成了碳凝胶/泡沫镍一体化电极,冷冻干燥处理后可得多孔碳凝胶/泡沫镍一体化电极. 水系和有机系的超级电容器测试表明,多孔碳凝胶/泡沫镍一体化电极具有较高的比容量和良好的循环稳定性,其独特的一体化电极组成和多孔结构有利于电子和电解液离子的有效传输.     

石墨烯基平面微型超级电容器的研究进展

便携式电子器件的快速发展极大地刺激了现代社会对多功能化、小型化的电化学储能器件的强烈需求.其中,微型超级电容器正逐渐成为芯片储能器件研究领域中一个新兴的、前沿的研究方向.它可作为微型功率源与微电子器件互相兼容,具有极大的应用前景.最近,以石墨烯为代表的二维材料为设计和发展新型平面化微型超级电容器提供了许多关键参数,引起了大家的关注.鉴于此,本文综述了石墨烯基平面微型超级电容器的最新进展,包括其发展历史、典型的石墨烯材料(如石墨烯、石墨烯量子点、活化石墨烯、石墨烯/碳纳米管、石墨烯/金属氧化物、石墨烯/聚合物)的制备、微型电极的构筑与加工(如光刻、电化学沉积、激光刻绘、喷涂印刷等)、电解液(如水系、有机系、离子液体和固态式)、微型器件构型组装(对称的、非对称的)和微型器件的评测方法.最后,展望了石墨烯基微型超级电容器未来的发展趋势和面临的挑战.     

碳基超级电容器电极材料的研究进展

超级电容器是近年迅速发展起来的一种新型储能元件,决定超级电容器性能的最重要因素是电极材料。碳材料以其比电容高、循环寿命长和资源丰富等优点,已经成为当前超级电容器电极材料的有力竞争者。用作超级电容器电极的碳材料主要包括活性炭、碳纳米管、石墨烯等。本文详细介绍了超级电容器用碳材料的特点、应用及发展状况,并指出制备具有大比表面积和高导电率的多孔碳是当前碳材料电极的主要研究方向。     

原位电化学合成铁基电极材料及其超级电容器性能（英文）

采用胶体纳米粒子为模型进行研究。假设活性阳离子均匀分布在导电碳与粘结剂中,电解液离子的渗入可以原位形成活性胶体团簇。通过原位电化学方法合成了不同组成的铁基超级电容器电极材料。在不同的阳离子电解液中,铁胶体离子电极的电容不同,其中在KOH、NaOH、LiOH电解液中分别为1 113、927、755 F·g~(-1)。通过胶体的介尺度结构构筑,实现离子到材料性能的跨尺度可控调节。通过对胶体模型的拓展,提供了原位组成调节到材料性能跨尺度调控的新方法。     

超级电容电池

本文比较了超级电容器、锂离子电池和超级电容电池的结构、原理、研究现状和发展前景。超级电容电池的正极具有超级电容器电极的结构和双电层储能机制,负极具有类似锂离子电池负极的结构和快速电化学储能机制。超级电容器和锂离子电池的发展空间都很有限,而作为两者结合的产物的超级电容电池可兼具高比功率、高比能量、高放电电压和长循环寿命的优点,是未来储能电池的发展方向之一,但还面临缺乏具有高分解电压的电解液和高充电电压下电解液中离子枯竭的问题。     

离子液体电解质种类对活性炭电极超级电容器电化学性能的影响

本文将经水蒸气二次活化的椰壳活性炭（W-AC）作为电极材料,选择1-乙基-3甲基咪唑四氟硼酸盐（[EMIM]BF₄）作为电解质,结果表明W-AC电极的比电容量远高于未活化的椰壳活性炭（R-AC）.使用循环伏安、恒电流充放电、交流阻抗等方法研究了不同种类离子液体电解质对超级电容器电化学性能的影响.不同阴阳离子组成的离子液体作为电解质,直接影响超级电容器的电化学性能. 研究表明,由EMIM⁺和BMIM⁺阳离子与BF₄^-、TFSI^-阴离子构成的离子液体电解质较适用于W-AC电极. 其中在[EMIM]BF₄电解质中,单片电极的比电容量可高达153 F·g^-1;在1-丁基-3-甲基-咪唑四氟硼酸盐（[BMIM]BF₄）电解质中电位窗可达3.5V,能量密度可高达57 Wh·kg^-1.本研究对于构筑高性能超级电容器离子液体的选择提供参考,以满足不同应用领域需求.     

Performance of PbO2/activated carbon hybrid supercapacitor with carbon foam substrate

PbO₂/activated carbon（AC） hybrid supercapacitor in H₂SO₄ with a carbon foam current collector is studied.The PbO₂/AC hybrid is designed with electrodeposited PbO₂ thin film as positive electrode to match with AC negative electrode.The discharge curve shows capacitive characteristics between 1.88 V and 0.65 V.The hybrid system exhibits excellent energy and power performance,with specific energy of 43.6 Wh/kg at a power density of 654.2 W/kg.The use of carbon foam current collector ensures stability of the PbO₂ electrode in H₂SO₄ environment.After 2600 deep cycles at 15 C high rate of charge/discharge,the capacity remains nearly unchanged from its initial value.     

Quantification of the Charge Consuming Phenomena under High‐Voltage Hold of Carbon/Carbon Supercapacitors by Coupling Operando and Post‐Mortem Analyses

Enhancing the operating voltage of supercapacitors (SCs), hence their specific energy, is important. However, long‐term hold at high voltage entails loss of capacitance, increase of resistance and internal pressure. Such detrimental effects could be reduced by obtaining quantitative information on the relative impact of the various mechanisms leading to the worsening of the SCs performance. Now, for a carbon/carbon supercapacitor in aqueous Li₂SO₄, a self‐consistent approach is used to assign leaking charge during high voltage hold to the charge: 1) distributed throughout the electrochemical cell (steady‐state leakage current measurements), 2) spent at each electrode for gases production (operando electrochemical mass spectrometry (EMS) analysis and pressure records), 3) utilized to oxidize the electrodes surface (from post‐mortem surface functionality determination by temperature programmed desorption (TPD)), and 4) used for other parasitic reactions.     

Surface modification by graphene oxide:An efficient strategy to improve the performance of activated carbon based supercapacitors

An efficient and cost-effective strategy to modificate the surface of active carbon (AC), form a 3D-conductive network, and therefore improve the electrochemical performance of AC based supercapacitor was developed.     

碳钢/醇酸涂层在5%NaCl溶液中的极化及半导体行为

摘要 采用电位-电容测试和Mott-Schottky分析技术研究了碳钢/醇酸涂层在5%NaCl溶液侵蚀下腐蚀失效过程中的极化及半导体行为. 浸泡2h, 电极形成了MIS结构, 涂层半导体为n型导电, 半导体载流子密度为4.99×109cm-3, 腐蚀仅受水和离子在涂层中的扩散控制;浸泡1d和2d时, 涂层在电场下发生偶极极化, 偶极电场阻碍载流子的迁移, 偶极弛豫效应使微分电容随外加电位绝对值增大而减小, 并造成电位-电容行为的频率依赖性;浸泡7d~17d涂层发生空间电荷极化, 碳钢与涂层形成了金属/半导体接触, 随着浸泡时间延长, 涂层载流子密度逐渐增加, 平带电位正移, 功函数逐渐减小, 对电子束缚能力减弱, 随外加电位的增加, 金属/醇酸涂层界面势垒升高, 空间电荷层成为阻挡层, 电极载流子输运受涂层孔隙电阻, 空间电荷层, 金属基底反应动力学三重控制.     

Electrochemical characterization of Ni-Co and Ni-Co-Fe for oxidation of methyl alcohol fuel w ith high energetic catalytic surface*简

 Non Pt based metals and alloys as electrode materials for methyl alcohol fuel cells have been investigated with an aim of finding high electrocatalytic surface property for the faster electrode reactions. Electrodes were fabricated by electrodeposition on pure Al foil, from an electrolyte of Ni, Co, Fe salts. The optimum condition of electrodeposition were found out by a series of experiments, varying the chemistry of the electrolyte, pH valve, temperature, current and cell potential. Polarization study of the coated Ni-Co or Ni-Co-Fe alloy on pure Al was found to exhibit high exchange current density, indicating an improved electro catalytic surface with faster charge-discharge reactions at anode and cathode and low overvoltage. Electrochemical impedance studies on coated and uncoated surface clearly showed that the polarization resistance and impedance were decreased by Ni-Co or Ni-Co-Fe coating. X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX) and atomic absorption spectroscopy (AAS) studies confirmed the presence of alloying elements and constituents of the alloy. The morphology of the deposits from scanning electron microscope (SEM) images indicated that the electrode surface was a three dimensional space which increased the effective surface area for the electrode reactions to take place.     

Boosting the Energy Density of Carbon‐Based Aqueous Supercapacitors by Optimizing the Surface Charge

The voltage of carbon‐based aqueous supercapacitors is limited by the water splitting reaction occurring in one electrode, generally resulting in the promising but unused potential range of the other electrode. Exploiting this unused potential range provides the possibility for further boosting their energy density. An efficient surface charge control strategy was developed to remarkably enhance the energy density of multiscale porous carbon (MSPC) based aqueous symmetric supercapacitors (SSCs) by controllably tuning the operating potential range of MSPC electrodes. The operating voltage of the SSCs with neutral electrolyte was significantly expanded from 1.4 V to 1.8 V after simple adjustment, enabling the energy density of the optimized SSCs reached twice as much as the original. Such a facile strategy was also demonstrated for the aqueous SSCs with acidic and alkaline electrolytes, and is believed to bring insight in the design of aqueous supercapacitors.     

High-speed carbon nanotube actuators based on an oxidation/reduction reaction

Actuators with a high-speed response under a high-frequency (more than 100 Hz) applied square-wave voltage of ±2 V have been developed with an electrode composed of millimeter-long single-walled carbon nanotubes synthesized by the "supergrowth method" (SG-SWNTs) and ionic liquids (ILs). Detailed studies concerning induced electric current and transferred charge in the electrode as well as cyclic voltammetric studies of the electrode revealed that the high-speed response originates from the electric current generated by an oxidation/reduction (redox) reaction in addition to electric double-layer charging. The contribution of the redox reactions of SG-SWNTs to the actuation is sensitive to the presence of supporting polymers, the thickness of the electrolyte, and the amplitude of the applied voltage.     

基于NiCo2O4纳米片电极的非对称混合电容器

The looming global energy crisis and ever-increasing energy demands have catalyzed the development of renewable energy storage systems. In this regard, supercapacitors (SCs) have attracted widespread attention because of their advantageous attributes such as high power density, excellent cycle stability, and environmental friendliness. However, SCs exhibit low energy density and it is important to optimize electrode materials to improve the overall performance of these devices. Among the various electrode materials available, spinel nickel cobaltate (NiCo₂O₄) is particularly interesting because of its excellent theoretical capacitance. Based on the understanding that the performances of the electrode materials strongly depend on their morphologies and structures, in this study, we successfully synthesized NiCo₂O₄ nanosheets on Ni foam via a simple hydrothermal route followed by calcination. The structures and morphologies of the as-synthesized products were characterized by X-ray diffraction, scanning electron microscopy, and Brunauer-Emmett-Teller (BET) surface area analysis, and the results showed that they were uniformly distributed on the Ni foam support. The surface chemical states of the elements in the samples were identified by X-ray photoelectron spectroscopy. The as-synthesized NiCo₂O₄ products were then tested as cathode materials for supercapacitors in a traditional three-electrode system. The electrochemical performances of the NiCo₂O₄ electrode materials were studied and the area capacitance was found to be 1.26 C·cm^-2 at a current density of 1 mA·cm^-2. Furthermore, outstanding cycling stability with 97.6% retention of the initial discharge capacitance after 10000 cycles and excellent rate performance (67.5% capacitance retention with the current density from 1 to 14 mA·cm^-2) were achieved. It was found that the Ni foam supporting the NiCo₂O₄ nanosheets increased the conductivity of the electrode materials. However, it is worth noting that the contribution of nickel foam to the areal capacitance of the electrode materials was almost zero during the charge and discharge processes. To further investigate the practical application of the as-synthesized NiCo₂O₄ nanosheets-based electrode, a device was assembled with the as-prepared samples as the positive electrode and active carbon (AC) as the negative electrode. The assembled supercapacitor showed energy densities of 0.14 and 0.09 Wh·cm^-3 at 1.56 and 4.5 W·cm^-3, respectively. Furthermore, it was able to maintain 95% of its initial specific capacitance after 10000 cycles. The excellent electrochemical performance of the NiCo₂O₄ nanosheets could be ascribed to their unique spatial structure composed of interconnected ultrathin nanosheets, which facilitated electron transportation and ion penetration, suggesting their potential applications as electrode materials for high performance supercapacitors. The present synthetic route can be extended to other ternary transition metal oxides/sulfides for future energy storage devices and systems.