基于阻抗综合的碳基超级电容器性能仿真

根据超级电容器等效电路模型的分析和复数阻抗综合方法,经试验数据拟合优化,建立了超级电容器等效阻抗函数。通过该函数仿真了超级电容器的电压、电能容量、电流和荷电状态等性能指标的动态特征。经试验验证,该函数可预测超级电容器在充、放电过程中的电流、电压和荷电状态的动态变化。

石墨烯/δ-MnO_(2)复合材料及其超级电容器性能研究

文章采用共同沉积法制备石墨烯/MnO_(2)复合材料,研究五种不同质量比的石墨烯和MnO_(2)对复合材料结构以及超级电容器性能的影响。实验结果显示:复合材料中的MnO_(2)为α型MnO_(2),其中当石墨烯的质量分数为27.5%时,石墨烯/MnO_(2)复合材料具备较好电容器性能,当使用6mol/L氢氧化钾溶液作为电解质时,石墨烯/MnO_(2)复合材料具备较好电化学可逆性能。

北航“高性能超级电容器用纳米材料与技术”顺利通过课题验收

近日，北京航空航天大学工程训练中心与防化研究院合作研究的国家863专项项目“高性能超级电容器用纳米材料与技术”顺利通过课题验收。

Co_3O_4/氮掺杂三维石墨烯材料制备及电容性能

通过两步法制备Co_3O_4/氮掺杂三维石墨烯,先使用不同pH的NH_3-NH_4^+缓冲溶液制得前驱体,之后煅烧前驱体制得复合材料。电化学测试结果表明,在pH=9.75时制备的复合材料电化学性能最好,在电流密度为1 A/g下的比电容值为630.6 F/g,电流密度增大到2 A/g时,电容保持率为87%,经过1 000次充放电测试后,电容保持率仍高达87%,且材料内阻小于1Ω。XRD和SEM测试表明,复合材料为非晶形材料且呈蜂窝状结构。

Electrochemical Performance of Nickel Hydroxide/Activated Carbon Supercapacitors Using a Modified Polyvinyl Alcohol Based Alkaline Polymer Electrolyte

Polyvinyl alcohol （PVA）-sodium polyacrylate （PAAS）-KOH-H2O alkaline polymer electrolyte film with high ionic conductivity was prepared by a solution-casting method. Polymer Ni（OH）2/activated carbon （AC） hybrid supercapacitors with different electrode active material mass ratios （positive to negative） were fabricated using this alkaline polymer electrolyte, nickel hydroxide positive electrodes, and AC negative electrodes. Galvanostatic charge/ discharge and electrochemical impedance spectroscopy （EIS） methods were used to study the electrochemical performance of the capacitors, such as charge/discharge specific capacitance, rate charge/discharge ability, and charge/discharge cyclic stability. Experimental results showed that with the decreasing of active material mass ratio m（Ni（OH）2）/m（AC）, the charge/discharge specific capacitance increases, but the rate charge/discharge ability and the charge/discharge cyclic stability decrease.

Synthesis of mesoporous carbon as electrode material for supercapacitor by modified template method

The pore structures and electrochemical performances of mesoporous carbons prepared by silica sol template method as electrode material for supercapacitor were investigated. The mean pore size and mass specific capacitance of the mesoporous carbons increase with the increase of mass ratio of silica sol to carbon source （glucose）. A modified template method, combining silica sol template method and ZnCl2 chemical activation method, was proposed to improve the mass specific capacitance of the mesoporous carbon with an improved BET surface area. The correlation of rate capability and pore structure was studied by constant current discharge and electrochemical impedance spectroscopy. A commercially available microporous carbon was used for comparison. The result shows that mesoporous carbon with a larger pore size displays a higher rate capability. Mesoporous carbon synthesized by modified template method has both high mass specific capacitance and good rate capability.

Excellent supercapacitive performance of a reduced graphene oxide/Ni(OH)_2 composite synthesized by a facile hydrothermal route

A reduced graphene oxide/Ni(OH)2 composite with excellent supercapacitive performance was synthesized by a facile hydrothermal route without organic solvents or templates used.XRD and SEM results reveal that the nickel hydroxide,which crystallizes into hexagonal β-Ni(OH)2 nanoflakes with a diameter less than 200 nm and a thickness of about 10 nm,is well combined with the reduced graphene oxide sheets.Electrochemical performance of the synthesized composite as an electrode material was investigated by cyclic voltammetry,electrochemical impedance spectroscopy and galvanostatic charge/discharge measurements.Its specific capacitance is determined to be 1672 F/g at a scan rate of 2 mV/s,and 696 F/g at a high scan rate of 50 mV/s.After 2000 cycles at a current density of 10 A/g,the composite exhibits a specific capacitance of 969 F/g,retaining about 86% of its initial capacitance.The composite delivers a high energy density of 83.6 W·h/kg at a power density of 1.0 kW/kg.The excellent supercapacitive performance along with the easy synthesis method allows the synthesized composite to be promising for supercapacitor applications.

Hybrid supercapacitor based on polyaniline doped with lithium salt and activated carbon electrodes

Polyaniline（PANI） nanofiber was synthesized by interfacial polymerization utilizing the interface between HC1 and CCl4. The hybrid type supercapacitors （PLi/C） based on Li-doping polyaniline and activated carbon electrode were fabricated and compared with the redox type capacitors （PLi/PLi） based on two uniformly Li-doping polyaniline electrodes. The electrochemical performances of the two types of supercapacitors were characterized in non-aqueous electrolyte. PLi/C supercapacitors have a wider effective energy storage potential range and a higher upper potential. At the same time, the PLi/C supercapacitor exhibits a specific capacity of 120.93 F/g at initial discharge and retains 80% after 500 cycles. The ohmic internal resistance （REs） of PLi/C supercapacitor is 5.0 Ω, which is smaller than that of PLi/PLi capacitor （5.5 Ω）. Moreover, it can be seen that EtgNBF4 organic solution is more suitable for using as organic electrolyte of PLi/C capacitor compared with organic solution containing LiPFr.

Design of best performing hexagonal shaped Ag@CoS/rGO nanocomposite electrode material for electrochemical supercapacitor application

The mixed metal/metal sulphide(Ag@CoS)with reduced graphene oxide(rGO)nanocomposite(Ag@CoS/rGO)was synthesized for the possible electrode in supercapacitors.Ag@CoS was successfully deposited on the rGO nanosheets by hydrothermal method,implying the growth of 2D Ag and CoS-based hexagonal-like structure on the rGO framework.The synthesized nanocomposite was subjected to structural,morphological and electrochemical studies.The XRD results show that the prepared nanocomposite material exhibits a combination of hexagonal and cubic phase due to the presence of CoS and Ag phases together.The band appearing at nearly 470.33 cm^−1 in FTIR spectra can be ascribed to the absorption of S—S bond in the Ag@CoS/rGO nanocomposite.The clear hexagonal structure was analysed by SEM and TEM with the grain sizes ranging from nanometer to micrometer.The electrode material exhibits excellent cyclic stability with a specific capacitance of 1580 F/g at a current density of 0.5 A/g without any loss of capacitive retention even after 1000 cycles.Based on the electrochemical performance,it can be inferred that the prepared novel nanocomposite material is very suitable for using as an electrode for electrochemical supercapacitor applications.

High-performance porous carbon for supercapacitors prepared by one-step pyrolysis of PF/gelatin blends

A high-performance porous carbon material for supercapacitor electrodes was prepared by using a polymer blend method. Phenol-formaldehyde resin and gelatin were used as carbon precursor polymer and pore former polymer, respectively. The blends were carbonized at 800℃ in nitrogen. SEM, BET measurement and BJH method reveal that the obtained carbon possesses a mesoporous characteristic, with the average pore size between 3.0 nm and 5.0 nm. The electrochemical properties of supercapacitor using these carbons as electrode material were investigated by cyclic voltammetry and constant current charge-discharge. The results indicate that the composition of blended polymers has a strong effect on the specific capacitance. When the mass ratio of PF to gelatin is kept at 1：1, the largest surface area of 222 m2/g is obtained, and the specific capacitance reaches 161 F/g.

Study on Activated Carbon for Electrode Material

Activated carbon （AC） was fabricated by Coconut shell as carbon source, KOH as activator. Cyclic voltammetry and galvanostatic charge-discharge were used to characterize the electrochemical performance of the samples. The results showed that： Supercapacitors based on the sample AC-3 have low Equivalent series resistanceb （ESR） and excellent power property.

Metallic mesocrystal nanosheets of vanadium nitride for high-performance all-solid-state pseudocapacitors

Transition metal nitrides （TMNs） are of particular interest by virtue of their synergic advantages of superior electrical conductivity, excellent environmental durability and high reaction selectivity, yet it is difficult to achieve flexible design and operation. Herein, mesocrystal nanosheets （MCNSs） of vanadium nitride （VN） are synthesized via a confined-growth route from thermally stable layered vanadium bronze, representing the first two-dimensional （2D） metallic mesocrystal in inorganic compounds. Benefiting from their single-crystalline-like long-range electronic connectivity, VN MCNSs deliver an electrical conductivity of 1.44×10^5 S/m at room temperature, among the highest values observed for 2D nanosheets. Coupled with their unique pseudocapacitance, VN MCNS-based flexible supercapacitors afford a superior volumetric capacitance of 1,937 mF/cm3. Nitride MCNSs should have wide applications in the energy storage and conversion fields because their intrinsic high conductivity is coupled with the reactivity of inorganic lattices.

Tailoring uniform γ-MnO2 nanosheets on highly conductive three-dimensional current collectors for high-performance supercapacitor electrodes

Recent efforts have focused on the fabrication and application of three- dimensional （3-D） nanoarchitecture electrodes, which can exhibit excellent electrochemical performance. Herein, a novel strategy towards the design and synthesis of size- and thickness-tunable two-dimensional （2-D） MnO2 nanosheets on highly conductive one-dimensional （l-D） backbone arrays has been developed via a facile, one-step enhanced chemical bath deposition （ECBD） method at a low temperature （-50 ℃）. Inclusion of an oxidizing agent, BrO3-, in the solution was crucial in controlling the heterogeneous nucleation and growth of the nanosheets, and in inducing the formation of the tailored and uniformly arranged nanosheet arrays. We fabricated supercapacitor devices based on 3-D MnO2 nanosheets with conductive Sb-doped SnO2 nanobelts as the backbone. They achieved a specific capacitance of 162 F·g-1 at an extremely high current density of 20 A·g% and good cycling stability that shows a capacitance retention of -92% of its initial value, along with a coulombic efficiency of almost 100% after 5,000 cycles in an aqueous solution of I M Na2SO4. The results were attributed to the unique hierarchical structures, which provided a short diffusion path of electrolyte ions by means of the 2-D sheets and direct electrical connections to the current collector by 1-D arrays as well as the prevention of aggregation by virtue of the well-aligned 3-D structure.

Facile electrodeposition of 3D concentration-gradient Ni-Co hydroxide nanostructures on nickel foam as high performance electrodes for asymmetric supercapacitors

Novel three-dimensional （3D） concentration-gradient Ni-Co hydroxide nanostructures （3DCGNC） have been directly grown on nickel foam by a facile stepwise electrochemical deposition method and intensively investigated as binder- and conductor-free electrode for supercapacitors. Based on a three- electrode electrochemical characterization technique, the obtained 3DCGNC electrodes demonstrated a high specific capacitance of 1,760 F·g^-1 and a remarkable rate capability whereby more than 62.5% capacitance was retained when the current density was raised from 1 to 100 A·g^-1. More importantly, asymmetric supercapacitors were assembled by using the obtained 3DCGNC as the cathode and Ketjenblack as a conventional activated carbon anode. The fabricated asymmetric supercapacitors exhibited very promising electrochemical performances with an excellent combination of high energy density of 103.0 Wh·kg^-1 at a power density of 3.0 kW·kg^-1, and excellent rate capability-energy densities of about 70.4 and 26.0 Wh·kg^-1 were achieved when the average power densities were increased to 26.2 and 133.4 kW·kg^-1, respectively. Moreover, an extremely stable cycling life with only 2.7% capacitance loss after 20,000 cycles at a current density of 5 A·g^-1 was achieved, which compares very well with the traditional doublelayer supercapacitors.

Effect of surface area and heteroatom of porous carbon materials on electrochemical capacitance in aqueous and organic electrolytes

A series of porous carbon materials with wide range of specific surface areas and different heteroatom contents had been prepared using polyaniline as carbon precursor and KOH as an activating agent. Effect of surface area and heteroatom of porous carbon materials on specific capacitance was investigated thoroughly in two typical aqueous KOH and organic 1-butyl-3- methylimidazolium tetrafluoroborate/acetonitirle electrolytes. The different trends of capacitance performance were observed in these two electrolytes. Electrochemical analyses suggested that the presence of faradaic interactions on heteroatom-enriched carbon materials in organic environment is less significant than that observed in aqueous electrolytes. Thus, in aqueous electrolyte, a balance between surface area and heteroatom content of activated porous carbon would be found to develop a supercapacitor with high energy density. In organic electrolyte, the capacitance performance of porous carbon is strongly dependent on the surface area. The results may be useful for the design of porous carbon-based supercapacitor with the desired capacitive performance in aqueous and organic electrolytes.

Highly stretchable pseudocapacitors based on buckled reticulate hybrid electrodes

In order to develop an excellent pseudocapacitor with both high specific capacitance and outstanding stretchability to match with other devices applicable in future wearable and bio-implantable systems, we focus our studies on three vital aspects： Stretchability of hybrid film electrodes, the interface between different components, and the integrated performance in stretchability and electrochemistry of supercapacitors based on single-walled carbon nanotube/ polyaniline （SWCNT/PANI） composite films on pre-elongated elastomers. Owing to the moderate porosity, the buckled hybrid film avoids the cracking which occurs in conventional stretchable hybrid electrodes, and both a high specific capacitance of 435 F.g-1 and a high strain tolerance of 140% have been achieved. The good SWCNT/PANI interfacial coupling and the reinforced solid electrolyte penetration structure enable the integrated pseudocapacitors to have stretch- resistant interfaces between different units and maintain a high performance under a stretching of 120% elongation, even after 1,000 cyclic elongations.

Hierarchical mesoporous Co_3O_4@ZnCo_2O_4 hybrid nanowire arrays supported on Ni foam for high-performance asymmetric supercapacitors

In this paper, hierarchical mesoporous Co3O4@ZnCo2O4 hybrid nanowire arrays（NWAs） on Ni foam were prepared through a two-step hydrothermal process associated with successive annealing treatment. The Co3O4@ZnCo2O4 hybrid NWAs exhibited excellent electrochemical performances with a high specific capacity of 1,240.5 C g^-1 at a current density of 2 mA cm^-2, with rate capability of 59.0%shifting from 2 to 30 mA cm^-2, and only a 9.1% loss of its capacity even after 3,000 cycles at a consistent current density of 10 mA cm^-2. An asymmetric supercapacitor（Co3O4@ZnCo2O4 NWAs｜｜activated carbon） was fabricated and exhibited a high specific capacity of 168 C g^-1 at a current density of 1 A g^-1. And a preferable energy density of 37.3 W h kg^-1 at a power density of 800 W kg^-1 was obtained. The excellent electrochemical performances indicate the promising potential application of the hierarchical mesoporous Co3O4@ZnCo2O4 hybrid NWAs in energy storage field.

Iron oxide encapsulated in nitrogen-rich carbon enabling high-performance lithium-ion capacitor

Lithium-ion capacitors(LICs)could combine the virtues of high power capability of conventional supercapacitors and high energy density of lithium-ion batteries.However,the lack of high-performance electrode materials and the kinetic imbalance between the positive and negative electrodes are the major challenge.In this study,Fe3O4 nanoparticles encapsulated in nitrogen-rich carbon(Fe3O4@NC)were prepared through a self-assembly of the colloidal Fe OOH with polyaniline(PANI)followed by pyrolysis.Due to the well-designed nanostructure,conductive nitrogen-rich carbon shells,abundant micropores and high specific surface area,Fe3O4@NC-700 delivers a high capacity,high rate capability and long cycling stability.Kinetic analyses of the redox reactions reveal the pseudocapacitive mechanism and the feasibility as negative material in LIC devices.A novel LIC was constructed with Fe3O4@NC-700 as the negative electrode and expanded graphene(EGN)as the positive electrode.The wellmatched two electrodes effectively alleviate the kinetic imbalance between the positive and negative electrodes.As a result,Fe3O4@NC-700//EGN LIC exhibits a wide operating voltage window,and thus achieves an ultrahigh energy density of 137.5 W h kg^-1.These results provide fundamental insights into the design of pseudocapacitive electrode and show future research directions towards the next generation energy storage devices.

Improving the volumetric specific capacitance of flexible polyaniline electrode:solution casting method and effect of reduced graphene oxide sheets

High volumetric specific capacitance is essential for flexible supercapacitors.In this paper,a flexible composite electrode with ultrahigh volumetric specific capacitance and good rate performance is designed and prepared.The film electrode is composed of non-porous compact polyaniline as the matrix and a small amount of reduced graphene oxide sheets as the conductive filler.The film is prepared by a newly developed solution casting method,where the casting solution is obtained by self-assembly of polyaniline and graphene oxide in a blended solution.A systematical investigation on the effect of reduced graphene oxide sheets reveals that they serve as both the conductive filler and the diffusion barrier.With the optimized reduced graphene oxide content,a large volumetric specific capacitance of 1354 F cm^−3 at 2.4 A cm^−3 is achieved,and good rate performance is also obtained because of the good ionic conductivity of polyaniline.This work provides a high performance electrode for flexible supercapacitors,and the solution casting method is also valuable in fabricating other organic electrode materials.

All-climate aqueous Na-ion batteries using “water-in-salt” electrolyte

Aqueous Na-ion batteries have been extensively studied for large-scale energy storage systems. However,their wide application is still limited by their inferior cycle stability(<3000 cycles) and poor temperature tolerance. Furthermore, many of the reported high rate behaviors are achieved at a low mass loading(<3 mg cm^(-2)) of the electrodes. Herein, we propose an aqueous Na-ion battery which includes a Ni-based Prussian blue(NiHCF) cathode, a carbonyl-based organic compound, 5,7,12,14-pentacenetetrone(PT)anode and a “water-in-salt” electrolyte(17 mol kg^(-1)NaClO_(4)in water). Its operation involves the reversible coordination reaction of the PT anode and the extraction/insertion of Na;in the NiHCF cathode. It is demonstrated that the wide internal spaces of the PT anode and NiHCF cathode can not only buffer the volumetric change induced by Na;storage, but also enable fast kinetics. The full cell exhibits a supercapacitor-like rate performance of 50 A g^(-1)(corresponding to a discharge or charge within 6.3 s)and a super-long lifespan of 15,000 cycles. Moreover, the excellent rate performance can still be preserved even with a high mass loading of the electrodes(15 mgNiHCFcm^(-2)and 8 mgPTcm^(-2)).Especially, the cell can work well in a wide temperature range, from-40 to 100 °C, showing a typical all-climate operation.