Preparation of activated graphene/activated carbon dry composite electrode and its application in supercapacitors

采用干法电极制备工艺成功制备了活性石墨烯/活性炭复合电极片,分别用扣式电容器和软包电容器考察活性石墨烯/活性炭复合电极的电化学性能。综合结果表明,复合电极中活性石墨烯的含量为10%（质量分数）较为合适,相较于纯活性炭电极,比容量提高了10.8%。本工作验证了活性石墨烯材料在商用超级电容器中的适用性,证实了活性石墨烯是一种非常具有实际应用价值的电极材料。但目前,活性石墨烯并未真正产业化,其成本远高于商用活性炭。在未来,如何解决活性石墨烯工程制备技术难题和降低成本是材料产业界亟待解决的难题。     

Supercapacitor electrodes based on polyaniline-silicon nanoparticle composite

A composite material formed by dispersing ultrasmall silicon nanoparticles in polyaniline has been used as the electrode material for supercapacitors. Electrochemical characterization of the composite indicates that the nanoparticles give rise to double-layer capacitance while polyaniline produces pseudocapacitance. The composite shows significantly improved capacitance compared to that of polyaniline. The enhanced capacitance results in high power (220 kW kg⁻¹) and energy-storage (30 Wh kg⁻¹) capabilities of the composite material. A prototype supercapacitor using the composite as the charge storage material has been constructed. The capacitor showed the enhanced capacitance and good device stability during 1000 charging/discharging cycles.     

Matching the positive and negative electrode based on hierarchical porous carbon supporting π-conjugated polymers composites for asymmetric organic supercapacitor

能量密度是制约超级电容器实际应用的关键因素,通过正负电极材料的比电容匹配,构建有机非对称超级电容器是提高能量密度的有效途径。本工作以活化分级孔碳（aHPC）作载体,以β-萘磺酸为软模板和掺杂酸,借助化学氧化聚合方法,分别制备出活化分级孔碳负载聚苯胺（aHPC@PANI）及活化分级孔碳负载聚1,5-二氨基蒽醌（aHPC@PDAA）纳米复合材料。结果显示,两种复合材料均呈现疏松多孔的结构,且聚合物以纳米尺度均匀沉积在活化多孔碳孔壁内外,这对提高活性物质利用率及其倍率性能十分有利。在1 A/g电流密度下,aHPC@PANI正极材料与aHPC@PDAA负极材料的比容量,分别达256.7 F/g（–0.6～0.8 V）及253 F/g（–2～-0.6 V）。所组装的aHPC@PANI//Et 4NBF4-AN//aHPC@PDAA有机非对称超级电容器呈现宽的电位窗口（2.8 V）,高的能量密度（65 W·h/kg,1.38 kW/kg,基于aHPC@PANI和aHPC@PDAA总质量）及优异的循环稳定性（循环5000次后其容量保持率高达90.2%）。     

Fabrication and electrochemical performances of porous carbon nanotubes/polyaniline-modified carbon nanotube fiber

通过低电压电泳沉积的方法在碳纳米管纤维（CNF）表面沉积多孔碳纳米管（CNTs）,然后在其表面电化学沉积一层聚苯胺（PANI）,得到CNTs@PANI三维多孔网络结构修饰的核-鞘型纤维电极材料。通过扫描电镜、透射电镜和拉曼光谱表征电极材料表面形貌和微观结构,并利用电化学工作站测试电化学性能,研究结果表明,沉积的多孔CNTs结构可以为PANI提供更多的氧化还原反应活性位点,而PANI也具有固定CNTs的作用,在电流密度为1 mA/cm²时,CNTs和PANI修饰的电极面积比电容达77.28 mF/cm²。以聚二甲基硅氧烷薄膜为基底、PVA-H₃PO₄为电解质制备的对称型固态柔性超级电容器在电流密度为0.25 mA/cm²时,面积比电容为61.25 mF/cm²,恒流充放电4000次后,电容值仍维持在80%,并且串联两个电容器可以点亮电压为1.8 V的LED灯泡。     

Study on preparation and electrochemical properties of biomass-derived spherical activated carbon

以生物质风化煤系腐殖酸（LHA）为炭质前驱体,通过溶剂蒸发和KOH活化方法制备了球形活性炭。使用扫描电子显微镜（SEM）、N2物理吸脱附仪等手段对球形活性炭形貌和孔道结构进行了表征;还将活性炭组装成扣式电容器,进行了充放电容量、循环伏安特性和交流阻抗行为等电化学性能测试。结果表明：所制备的球形活性炭具有良好的球形度,通过少量碱活化后球形活性炭BET表面积为2034 m2/g、总孔容为1.24 cm3/g、平均孔径为2.38 nm。同时,以球形活性炭作为电极材料应用于水系超级电容器后显示了优异的电化学性能,比电容可达到319 F/g,在进行10000次充放电后,比电容保持率为98.9%。此外,球形活性炭相比于颗粒活性炭具有更好的导电性,也展现了更加优异的倍率性能和循环性能。因此说明LHA基球形活性炭是一种有潜在优势的超级电容器材料。     

Improved low‐temperature performance of novel asymmetric supercapacitor with capacitor/battery‐capacitor construction

A concept for designing capacitor/battery‐capacitor asymmetric supercapacitor is proposed to improve low‐temperature capacitance, which consists of a capacitor‐type electrode (C) and a capacitor/battery‐type composite electrode (NiO/C). This construction overcomes the capacitor‐battery asymmetric supercapacitor's shortcoming of losing capacitance characteristics. By adjusting the NiO/C mass ratio to 1/2, the new NiO/C–C asymmetric supercapacitor maintains excellent capacitance feature (rectangular CV curves and symmetrical charge/discharge profiles) as well as enlarging the work potential to 1.5 V, showing improved low‐temperature capacitance in comparison with C‐C and NiO‐C constructions. It is believed to come from the decreased total inner resistance and charge‐transfer resistance due to the substitution of NiO electrode with NiO/C composite electrode in the asymmetric supercapacitor. Copyright © 2016 John Wiley & Sons, Ltd.     

Effect of poly(3,4-ethylenedioxythiophene) (PEDOT) in carbon-based composite electrodes for electrochemical supercapacitors

Electrochemical double layer supercapacitor cells were fabricated and tested using composite electrodes of activated carbon with carbon black and poly(3,4-ethylenedioxythiophene) (PEDOT), and an organic electrolyte 1 M TEABF₄/PC solution. The effect of PEDOT on the performance of the EDLC cells was explored and the cells were characterised by electrochemical impedance spectroscopy (EIS), cyclic voltammetry and galvanostatic charge-discharge. A generalised equivalent circuit model was developed for which numerical simulations were performed to determine the properties and parameters of its components from the EIS data. It was found that the proposed model fitted successfully the data of all tested cells. PEDOT enhanced the electrode and cell capacitance via its pseudo-capacitance effect up to a maximum value for an optimum PEDOT loading and greatly increased the energy density of the cell while the maximum power density has been still maintained at supercapacitor levels. Furthermore, PEDOT replaced PVDF as a binder and harmful solvent release was reduced during electrode processing. Activated carbon-carbon black composite electrodes with PEDOT as binder were found to have specific capacitance superior to that of activated carbon-carbon black electrodes with PVDF binder.     

Synthesis of PEDOT-modified graphene composite materials as flexible electrodes for energy storage and conversion applications

In this study, poly(3,4-ethylenedioxythiophene) (PEDOT)-modified graphene composite materials have been shown to exhibit excellent energy storage and conversion properties. Flexible, conducting and porous carbon cloth (CC) and graphene paper (GP)-modified CC (GP/CC) were used as substrates for comparison in all experiments. PEDOT was electrodeposited on these substrates, and their capacitance properties were measured for supercapacitor applications. Furthermore, the adsorption of size-selected Pt colloidal nanoparticles has also been performed using two substrates to form the electrode materials for fuel cell applications. We found that the PEDOT/GP/CC is the excellent flexible electrode material for both supercapacitors and fuel cells.     

Polypyrrole/carbon aerogel composite materials for supercapacitor

Polypyrrole (PPy)/carbon aerogel (CA) composite materials with different PPy contents are prepared by chemical oxidation polymerization through ultrasound irradiation and are used as active electrode material for supercapacitor. The morphology of PPy/CA composite is examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that PPy is deposited onto the surface of CA. As evidenced by cyclic voltammetry, galvanostatic charge/discharge test and EIS measurements, PPy/CA composites show superior capacitive performances to CA, moreover, the results based on cyclic voltammograms show that the composite material has a high specific capacitance of 433 F g⁻¹, while the capacitance of CA electrode is only 174 F g⁻¹. Although the supercapacitor used PPy/CA as active electrode material has an initial capacitance loss due to the instability of PPy, the specific capacitance after 500 cycles stabilizes nearly at a fixed value.     

Mn3O4 nanoparticles on activated carbonitride by soft chemical method for symmetric coin cell supercapacitors

Trimanganese tetraoxide (Mn₃O₄) is limited in supercapacitor application due to its poor electrical conductivity and cycle stability. An effective strategy for improving its electrochemical performance is to be combined with good conductive materials, such as carbon materials. A facile method was developed to prepare a Mn₃O₄/activated carbonitride composite (MONC) as electrode material for supercapacitor. Mn₃O₄ particles with small size were homogeneously grown on the surface of activated carbonitride (NC). Notably, the addition of NC not only improves the electrical conductivity of Mn₃O₄ but also serves as a supporting matrix to maintain the stability of the composite. Electrochemical characterization results show that the specific capacitance of the composite can reach 180 F/g at a current density of 0.5 A/g, which is two times higher than that of Mn₃O₄ at the same current density. After 2000 cycles, the specific capacitance of MONC can be maintained at 80.2% of the initial specific capacitance. The symmetric coin cell (SCC) assembled by MONC as positive and negative electrodes shows large voltage window, excellent cycle stability, and superior energy/power densities. This work will be one of important references for the application of other transition metal oxides in energy storage devices.     

Enhancement of the energy storage properties of supercapacitors using graphene nanosheets dispersed with metal oxide-loaded carbon nanotubes

Graphene nanosheets (GNs) dispersed with SnO₂ nanoparticles loaded multiwalled carbon nanotubes (SnO₂-MWCNTs) were investigated as electrode materials for supercapacitors. SnO₂-MWCNTs were obtained by a chemical method followed by calcination. GNs/SnO₂-MWCNTs nanocomposites were prepared by ultrasonication of the GNs and SnO₂-MWCNTs. Electrochemical double layer capacitors were fabricated using the composite as the electrode material and aqueous KOH as the electrolyte. Electrochemical performance of the composite electrodes were compared to that of pure GNs electrodes and the results are discussed. Electrochemical measurements show that the maximum specific capacitance, power density and energy density obtained for supercapacitor using GNs/SnO₂-MWCNTs nanocomposite electrodes were respectively 224 F g⁻¹, 17.6 kW kg⁻¹ and 31 Wh kg⁻¹. The fabricated supercapacitor device exhibited excellent cycle life with ∼81% of the initial specific capacitance retained after 6000 cycles. The results suggest that the hybrid composite is a promising supercapacitor electrode material.     

Energy storage in symmetric and asymmetric supercapacitors based in carbon cloth/polyaniline–carbon black nanocomposites

In this work, the construction of electrochemical capacitors using polyaniline–carbon black nanocomposites as electrode material is described. Symmetric and asymmetric cells were assembled. The active material was supported on carbon cloth acting as current collector as well. The electrolyte was H₂SO₄ 0.5 M, and the selected potential range was 1 V. The electrochemical behavior of the arrayed supercapacitors was studied by cyclic voltammetry and galvanostatic charge/discharge runs. At a constant current density of 0.3 A/g, a specific capacitance value of 1039 F/g was obtained for a symmetric assembly using both electrodes prepared with polyaniline and carbon black nanocomposites. When the set is asymmetric, being the positive electrode made of polyaniline and carbon black nanocomposites, the specific capacitance value is 1534 F/g. For the latter array, the specific power and energy density values are 300 W/kg and 426 Wh/kg at 0.3 A/g, and 13 700 W/kg and 28 Wh/kg at 13.7 A/g. These results suggest a good capacity of fast energy transfer. Moreover, this asymmetric supercapacitor demonstrated a high stability over 1000 cycles being the loss of only 5%. Copyright © 2015 John Wiley & Sons, Ltd.     

Pinecone biomass-derived activated carbon: the potential electrode material for the development of symmetric and asymmetric supercapacitors

Activated carbon, from biomass (pinecone), was synthesized by conventional pyrolysis/chemical activation process and utilized for the fabrication of supercapacitor electrodes. The pinecone-activated carbon synthesized with 1:4 ratio of KOH (PAC4) showed an increase in surface area and pore density with a considerable amount of oxygen functionalities on the surface. Moreover, PAC4, as supercapacitor electrode, exhibited excellent electrochemical performances with specific capacitance value ∼185 Fg⁻¹ in 1 M H₂SO₄, which is higher than that of nonactivated pinecone carbon and 1:2 ratio KOH-based activated carbon (PAC2) (∼144 Fg⁻¹). The systematic studies were performed to design various forms of devices (symmetric and asymmetric) to investigate the effect of device architecture and operating voltage on the performance and stability of the supercapacitors. The symmetric supercapacitor, designed utilizing PAC4 in H₂SO₄ electrolyte, exhibited a maximum device-specific capacitance of 43 Fg⁻¹ with comparable specific energy/power and excellent stability (∼96% after 10 000 cycles). Moreover, a symmetric supercapacitor was specially designed using PAC4, as a positive electrode, and PAC2, as a negative electrode, under their electrolytic ion affinity, and which operates in aqueous Na₂SO₄ electrolyte for a wide cell voltage (1.8 V) and showed excellent supercapacitance performances. Also, a device was assembled with poly(3,4-ethylene dioxythiophene) (PEDOT) nanostructure, as positive electrode, and PAC4, as a negative electrode, to evaluate the feasibility of designing a hybrid supercapacitor, using polymeric nanostructure, as an electrode material along with biomass-activated carbon electrode.     

Polyaniline-Acetylene black-Copper cobaltite based ternary hybrid material with enhanced electrochemical properties and its use in supercapacitor electrodes

A new system based on Polyaniline-Acetylene black-Copper cobaltite composite has been prepared and affirmed by XRD, UV, SEM, FTIR, and EDS characterizations. The rod-like texture of ternary hybrid system offered excellent electrochemical activity in comparison to single and binary systems. CV and CD results revealed outstanding redox behavior of the ternary hybrid electrodes. Ternary electrode (PACC) presented the highest specific capacitance value of 690 F/g at 1 mA/cm² current density. PACC electrode based symmetric supercapacitor had a specific capacitance of 137.25 Fg^-1 at 1 mA/cm² of current density. PACC symmetric supercapacitor had the highest specific power and specific energy of 3308.85 W.kg^-1 and 19.064 Wh.kg^-1, respectively. The ternary system provides less charge transfer resistance values compared to all other systems. Thermal stability of the ternary composite is way better than polyaniline, which is due to the contribution of copper cobaltite and acetylene black. The overwhelming characteristics of the ternary hybrid composite bring it to the limelight as an excellent candidate in the field of supercapacitors.     

Supercapacitive behaviors of activated mesocarbon microbeads coated with polyaniline

The polyaniline/activated mesocarbon microbeads (PANI/ACMB) composites are prepared by in situ chemical oxidation polymerization. Fourier infrared spectroscopy (FTIR), scanning electron microscope (SEM) and transmission electron microscope (TEM) have been utilized to characterize the structure and morphology of PANI/ACMB composites. It has been found that PANI is uniformly deposited on the surface of the ACMB to form the leechee-like morphology. The supercapacitive behaviors of the PANI/ACMB composites are investigated with cyclic voltammetry (CV), galvanostatic charge/discharge and cycle life measurements. The results obtained from cyclic voltammograms show that the composites have a maximum specific capacitance of 433.75 F g⁻¹. Moreover, the electrochemical performance of the coin supercapacitor used PANI/ACMB composites as electrode active material represents both high specific capacitance and excellent cycle stability, indicating that the PANI/ACMB composites will be a kind of potential electrode active materials with excellent specific capacitance and enhanced cycle life for application in high performance supercapacitors.     

Aqueous dispersed conducting polyaniline nanofibers: Promising high specific capacity electrode materials for supercapacitor

Aqueous dispersed conducting polyaniline nanofiber, new electrode material for supercapacitor, is prepared employing acidic phosphate ester as dopant for nanofibrous polyaniline emeraldine base, which is synthesized by polymerization of aniline using ferric nitrate as oxidant through pseudo-high dilution technique. Highly crystalline and uniform polyaniline fibers with thin diameter of 17-26 nm are obtained, the film from which shows electrical conductivity of 32 S cm⁻¹. The thin nanofibrous polyaniline is used as electrode material for supercapacitor and its performance is evaluated in non-protonic solvent system. It shows a specific capacitance as high as 160 F g⁻¹ at discharge rate of 0.4 A g⁻¹ from −1 V to 1 V in 1 mol L⁻¹ tetraethylammonium tetrafluoroborate/propylene carbonate solution, and the discharge/charge efficiency reaches 92%, indicating that it possesses good electrochemical reversibility. The high capacitance can be attributed to its relatively high surface area of 70 m² g⁻¹, which is 3-5 times higher than spherical polyaniline or thick fiberous polyaniline, leading to high utilization of the electroactive materials.     

Effect of NaI/I2 mediators on properties of PEO/LiAlO2 based all-solid-state supercapacitors

NaI/I₂ mediators and activated carbon were added into poly(ethylene oxide) (PEO)/lithium aluminate (LiAlO₂) electrolyte to fabricate composite electrodes. All solid-state supercapacitors were fabricated using the as prepared composite electrodes and a Nafion 117 membrane as a separator. Cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge/discharge measurements were conducted to evaluate the electrochemical properties of the supercapacitors. With the addition of NaI/I₂ mediators, the specific capacitance increased by 27 folds up to 150 F g⁻¹. The specific capacitance increased with increases in the concentration of mediators in the electrodes. The addition of mediators also reduced the electrode resistance and rendered a higher electron transfer rate between mediator and mediator. The stability of the all-solid-state supercapacitor was tested over 2000 charge/discharge cycles.     

Three-dimensional nitrogen rich bubbled porous carbon sponge for supercapacitor & pressure sensing applications

Three-dimensional (3D) porous carbonaceous materials offer numerous merits such as light-weight, high surface area, flexibility, and thus hold immense potential in energy storage applications. In this work, we report preparation of nitrogen-rich free-standing compressible porous neuron-like carbon sponge using commercially available kitchen sponge by a facile, cost-effective, and scalable synthetic strategy. The unique neuron-like bubbled interconnected carbon structure with enhanced N/O functionalities improves the electrochemical performance by providing sufficient space for ion transport and large accessible surface-active sites. This material also delivers high current response under compressive stress acting as a pressure sensor. This bubbled carbon material achieves an improved specific capacitance of 268.5 F g⁻¹ at 0.5 A g⁻¹. As a self-supporting electrode in a symmetrical supercapacitor cell, it still delivers a good specific capacitance of 167 F g⁻¹ at 0.35 A g⁻¹, retaining 92.5% of capacitance over 7000 charge/discharge cycles. Furthermore, the device delivers a maximum energy density of 14.8 Wh Kg⁻¹, demonstrating its immense potential for multi-functional applications owing to its unique features.     

All‐carbon hybrids for high performance supercapacitors

A hybrid nanostructure with partially reduced graphene oxide (rGO) and carbon nanofibers (CNFs) was fabricated and used as supercapacitor electrodes. A straightforward, environmentally friendly, and low‐cost microwave‐assisted reduction process was developed for the synthesis of rGO/CNF hybrid structures. The fabricated supercapacitor devices showed a specific capacitance of 95.3 F g^?1 and a superior long‐term cycling stability. A capacitance retention of more than 97% after 11 000 galvanostatic charge discharge cycles was obtained. These and other results reported in this paper indicate that high‐rate, all‐carbon, rGO/CNF hybrid nanostructures are highly promising supercapacitor electrode materials.     

The preparation and performance of calcium carbide-derived carbon/polyaniline composite electrode material for supercapacitors

Calcium carbide (CaC₂)-derived carbon (CCDC)/polyaniline (PANI) composite materials are prepared by in situ chemical oxidation polymerization of an aniline solution containing well-dispersed CCDC. The structure and morphology of CCDC/PANI composite are characterized by Fourier infrared spectroscopy (FTIR), scanning electron microscope (SEM), transmission electron microscopy (TEM) and N₂ sorption isotherms. It has been found that PANI was uniformly deposited on the surface and the inner pores of CCDC. The supercapacitive behaviors of the CCDC/PANI composite materials are investigated with cyclic voltammetry (CV), galvanostatic charge/discharge and cycle life measurements. The results show that the CCDC/PANI composite electrodes have higher specific capacitances than the as grown CCDC electrodes and higher stability than the conducting polymers. The capacitance of CCDC/PANI composite electrode is as high as 713.4 F g⁻¹ measured by cyclic voltammetry at 1 mV s⁻¹. Besides, the capacitance retention of coin supercapacitor remained 80.1% after 1000 cycles.