基于原位聚合凝胶电解质的碳纳米笼//三氧化钨纳米棒超级电容器

发展非对称超级电容器可有效提升超级电容器能量密度,选择电极材料和电解质是关键.分级结构碳纳米笼因具有比表面积大、微孔-介孔-大孔共存、导电性好、稳定性高等优点,特别适合用作超级电容器电极材料.进一步通过N,S共掺杂引入赝电容、改善浸润性,所得的氮硫共掺杂碳纳米笼(NSCNC)在1 mol·L-1 H29O4溶液、电势范...     

SnO_2/石墨纳米片复合电极及其在超级电容器中的应用

在电场的作用下对石墨棒进行电化学剥离,使其表面形成相互平行排列,且垂直于石墨棒基底的二维(2D)石墨纳米片阵列(GNSA).然后通过阴极还原电沉积法制备Sn O2/石墨纳米片阵列(Sn O2/GNSA)复合电极.采用场发射扫描电镜(FE-SEM)、X射线衍射(XRD)和傅里叶变换红外(FT-IR)光谱对其形貌和结构进行了表征.电化学测试表明该复合电极具有优异的超电容性能,在0.5 mol·L-1Li NO3电解质中,扫描速率为5 m V·s-1,电位窗口为1.4 V时,比电容达4015 F·m-2.由Sn O2/GNSA复合电极和相同电解质组装成的对称型超级电容器,在扫描速率为5 m V·s-1时,其电位窗口可增至1.8 V,能量密度达到0.41 Wh·m-2,循环5000圈后其比电容仍保持为初始比电容的81%.     

基于玉米秸秆合成的多孔生物质炭材料及其电化学储能

以玉米秸秆为原料,合成了高比表面积(2167 m²/g)的多孔生物质炭材料。 优化实验条件即可获得性能最佳的生物质炭电极材料,其在电流密度为1 A/g时的比电容高达390 F/g。 更重要的是,以所得最佳多孔生物质炭为电极材料,3 mol/L 的KOH溶液为电解质,组装了液相对称超级电容器。 该超级电容器在功率密度为818 W/kg时,其能量密度高达7 Wh/kg,在循环10000圈后的电容保持率为91.1%。 同时,将两个这种超级电容器串联充电之后,能够点亮15个LED灯并驱动小风扇正常工作。 这些结果表明,将基于玉米秸秆的多孔生物质炭作为先进电极材料应用于超级电容器具有较大的实际应用价值。     

MnO2电沉积直立碳纳米管制备超级电容器的研究

以直立碳纳米管为基底,以pH=6.0的0.1mol/L Na2SO4 为底液,采用电化学沉积法在0.2 mol/L Mn(CH3COO)2溶液中制备了直立碳纳米管与二氧化锰复合材料。SEM测试结果表明复合材料表面呈现多孔状结构。通过循环伏安,恒流充放电,交流阻抗等电化学方法对复合材料修饰电极进行电容性质测试。实验结果表明,在1mol/L KCl 溶液中,0-0.6V(vs. 银/氯化银参比)电位窗口内此复合材料表现出优良的超电容性能。直立碳纳米管电极的比电容为16 F/g,在碳纳米管表面沉积上二氧化锰修饰层后,此复合材料电极的比电容增大至330 F/g,比电容量大幅提升近20倍。同时扫描200圈后,直立碳纳米管与二氧化锰复合材料的循环伏安曲线变化很小,说明其具有相当好的循环寿命和电容稳定性能。     

石墨烯/聚吡咯纳米纤维超级电容器电极材料的制备及其电化学性能

超级电容器因其具有较高的循环稳定性和较好的能量密度而成为储能器件中的研究热点,其电极材料及制备方法是决定超级电容器电化学性能的关键因素。 本文以聚环氧乙烷-聚环氧丙烷-聚环氧乙烷三嵌段共聚物(P123)为软模板,通过一步原位聚合法成功地制备了石墨烯/聚吡咯纳米纤维(GR/PPy NF)复合超级电容器电极材料。 通过X射线衍射(XRD),X射线光电子能谱(XPS)、透射电子显微镜(TEM)和傅里叶变换红外光谱仪(FT-IR)等对复合材料的结构和形态进行了系统的表征。 利用电化学方法对GR/PPy NF复合电极材料的电化学性能进行了系统的分析。 结果表明,在电流密度0.5 A/g下,纳米复合材料的比电容量高达969.5 F/g,在充放电600圈之后,仍可保留初始比电容的88%,展示了良好的电容性能及循环稳定性。 GR/PPy NF制备简单,性能优异,是一种很有前途的能量转换/存储材料。     

MnO2电沉积直立碳纳米管制备超级电容器

以直立碳纳米管为基底,以pH=6.0的0.1 mol/L Na2SO4为底液,采用电化学沉积法在0.2 mol/L Mn(CH3COO)2溶液中制备了直立碳纳米管与MnO2复合材料. SEM测试结果表明,复合材料表面呈现多孔状结构. 通过循环伏安、恒流充放电、交流阻抗等电化学方法对复合材料修饰电极进行电容性质测试. 结果表明,在1 mol/L KCl溶液中,0～0.6 V(vs.Ag/AgCl参比)电位窗口内此复合材料表现出优良的超电容性能. 直立碳纳米管电极的比电容为16 F/g,在碳纳米管表面沉积上MnO2修饰层后,复合材料电极的比电容增大至330 F/g,比电容量大幅提升近20倍. 同时扫描200圈后,直立碳纳米管与MnO2复合材料的循环伏安曲线变化很小,具有相当好的循环寿命和电容稳定性能.     

离子液体在多孔碳电极上的电化学性能

制备了数种离子液体及离子液体有机溶液电解质,用线性电位扫描法测试了它们的电化学窗口;并通过循环伏安、交流阻抗、电势阶跃等电化学方法,对它们在多孔碳电极中的电化学性能进行了研究.实验结果表明:溶剂对1-乙基-3-甲基咪唑类离子液体有机溶液电解质的电化学窗口有较大的影响.离子液体及离子液体有机溶液电解质在多孔碳电极上的电化学性能与其电导率密切相关,电导率越大,充电时间常数越小,比容量越大;但比容量降低的倍率远小于电导率降低的倍率.     

基于过渡金属硫化物/还原氧化石墨烯复合物的高性能超级电容器

组装高能量密度的非对称超级电容器需要使用比电容大、 体积变化小且循环稳定性好的电极材料. 过渡金属硫化物(TMSs)与纳米碳材料的复合物是此类电极材料之一. 采用水热法合成了由Cu-Mo硫化物在微波剥离的还原氧化石墨烯表面生长的复合材料(CuS-MoS₂/MErGO). 此复合材料在电流密度为2 A/g时具有高达861.5 F/g的比电容和良好的循环稳定性. 将1.6 V的电池电压施加在由NiS/MErGO为正极, CuS-MoS₂/MErGO为负极组装成的不对称超级电容器上时, 该电容器的功率密度为1.28 kW/kg, 且能量密度保持为54.2 W·h·kg^-1. 结果表明, TMS复合材料是一种很有前途的高性能电化学储能材料, 尤其是用于非对称超级电容器的组装.     

激光直写微型RGO/MWCNT/CF平面柔性超级电容器的制备及性能

将采用改性Hummers法制备的氧化石墨烯与多壁碳纳米管(MWCNT)复合, 通过激光直写的方法制备了以棉织物(Cotton fabric, CF)为基底的石墨烯复合碳纳米管的同心圆形织物柔性平面超级电容器(RGO/MWCNT/CF). 通过扫描电子显微镜、 X 射线衍射和拉曼光谱技术对RGO/MWCNT/CF进行了表征, 并对超级电容器的电导率和电化学性能进行了测试. 结果表明, 电极材料经激光还原后导电率达到了7.19×10 ⁴ S/m, 表现出良好的导电性能. 以RGO/MWCNT/CF为工作电极、 PVA/LiCl凝胶为电解质组装的超级电容器具有良好的电化学性能, 在电位窗口为0~1 V、 电流密度为40.8 mA/cm ²时比电容达到24 mF/cm ², 功率密度为61 mW·h/kg, 能量密度为1.22 mW·h/kg, 且循环1000次仍能保持92%的比电容.     

氮掺杂石墨烯量子点/MOF衍生多孔碳纳米片构筑高性能超级电容器

首先采用溶液法在碳布上生长Co-MOF二维纳米片,通过高温退火和刻蚀后得到MOF衍生多孔碳纳米片。以Co-MOF衍生的多孔碳纳米片/碳布(CNS/CC)作为碳基骨架,采用电化学沉积法负载高活性氮掺杂石墨烯量子点(N-GQDs),制备得到分级多孔结构的N-GQD/CNS/CC复合材料。组装成自支撑且无粘结剂的N-GQD/CNS/CC电极,当电流密度为1 A·g~(-1)时,其比电容高达423 F·g~(-1)。通过储能机制和电容贡献机制的研究表明,在碳纤维上原位生长的具有高双电层电容的CNS和表面负载具有高赝电容的N-GQDs之间相互协同作用,使得N-GQD/CNS/CC电极具有高电容性能,是一种理想的超级电容器电极材料。电极材料的高导电、分级多孔结构有利于电子的传输和电解质离子的扩散,具有良好的动力学性能,能快速充放电和具有优异的倍率特性。将电极组装成对称型超级电容器,功率密度为250 W·kg~(-1)时对应的能量密度达到7.9 Wh·kg~(-1),且经过10 000次循环后电容保持率为91.2%,说明氮掺杂石墨烯量子点/MOF衍生多孔碳纳米片复合材料是一种电化学性能稳定的具有高电容性能的全碳电极材料。     

N,O co-doped porous carbon with rich pseudocapacitive groups exhibiting superior energy density in an acidic 2.4 V Li2SO4 electrolyte

Designing a carbon material with a unique composition and surface functional groups for offering high specific capacity in a wide voltage window is of great significance to improve the energy density for the supercapacitor in a cheap and eco-friendly aqueous electrolyte. Herein, we develop an efficient strategy to synthesize a N, O co-doped hierarchically porous carbon (NODPC-1.0) with moderate specific surface area and pore volume as well as rich heteroatoms using a deep eutectic solvent (DES) as an activator. It is found that NODPC-1.0 with a large proportion of pseudocapacitive functional groups (pyrrole-N, pyridine-N and carbonyl-quinone) can work stable in an acidic 2 mol/L Li₂SO₄ (pH 2.5) electrolyte, exhibiting specific capacities of 375 and 186 F/g at the current densities of 1.0 and 100 A/g, respectively. Also, the assembled symmetric capacitor using the NODPC-1.0 as the active material and 2 mol/L acidic Li₂SO₄ (pH 2.5) as the electrolyte shows an outstanding energy density of 74.4 Wh/kg at a high power density of 1.44 kW/kg under a broad voltage window (2.4 V). Relevant comparative experiments indicate that H⁺ of the acidic aqueous electrolyte plays a crucial part in enhancement the specific capacity, and the abundant pseudocapacitive functional groups on the surface of the NODPC-1.0 sample play the key role in the improvement of electrochemical cycle stability under a broad voltage window.     

水系锌离子电容器

本文首次提出了一种水系锌离子电容器的新型储能体系,其中以五氧化二钒（V₂O₅）为正极,具有高比表面积的活性炭（AC）为负极,以及三氟甲基磺酸锌（Zn(TfO)₂）为电解质. X射线衍射（XRD）证明二价锌离子作为电荷载体,可以在五氧化二钒（V₂O₅）中进行可逆的嵌入与脱出. 该锌离子电容器的电位窗口可达1.4 V,具有良好的倍率特性及循环稳定性. 电流密度为1000 mA·g^-1 时,电容器的比能量密度为4.5 Wh·kg^-1,功率密度可达181 W·kg^-1. 本工作为发展新型基于多价离子电化学电容器提供了新思路和新方法.     

Preparation of safe water–lipid mixed electrolytes for application in ion capacitor

Aqueous electrolytes are safe, economic, and environmentally friendly. However, they have a narrow potential window. On the other hand, organic electrolytes exhibit good thermodynamic stability but are inflammable and moisture sensitive. In this study, we prepared water–PEG–lipid ternary electrolytes(TEs). To combine the advantages of water, polyethylene glycol(PEG) and propylene carbonate(PC). The nonflammable mixed electrolytes exhibited a wide potential window of about 2.8 V due to the beneficial effects of PEG and PC. Using these TEs, a lithium manganate–active carbon ion capacitor could be operated at 2.4 V with an energy density of 32 Wh/kg, based on the total active electrode material(current density of 3.3 m A/cm~2). This value was significantly higher than that achieved using an aqueous electrolyte, thereby rationalizing the higher energy density.     

Extraordinary Supercapacitor Performance of a Multicomponent and Mixed‐Valence Oxyhydroxide

We report a novel multicomponent mixed‐valence oxyhydroxide‐based electrode synthesized by electrochemical polarization of a de‐alloyed nanoporous NiCuMn alloy. The multicomponent oxyhydroxide has a high specific capacitance larger than 627 F cm^?3 (1097±95 F g^?1) at a current density of 0.25 A cm^?3, originating from multiple redox reactions. More importantly, the oxyhydroxide electrode possesses an extraordinarily wide working‐potential window of 1.8 V in an aqueous electrolyte, which far exceeds the theoretically stable window of water. The realization of both high specific capacitance and high working‐potential windows gives rise to a high energy density, 51 mWh cm^?3, of the multicomponent oxyhydroxide‐based supercapacitor for high‐energy and high‐power applications.     

Cobalt–iron decorated tellurium nanotubes for high energy density supercapacitor

We report the synthesis of cobalt-iron (Co–Fe) decorated tellurium nanotubes (Te NTs) using semiconductive Te NTs as a sacrificial template, following a wet chemical method. The interplay of Co and Fe precursor concentrations incorporated with Te NT, residual hydrazine hydrate, and the negative surface charge of Te NT plays a significant role in obtaining various bimetallic telluride structures. The one-dimensional (1-D) structure of Co–Fe decorated Te NTs with Te NTs in the backbone provides superior conductivity and exhibits high electrochemical performance with battery type electrode behavior. A negative surface charge value of ?18.9 mV for Te NTs is obtained due to the presence of an anionic surfactant as sodium dodecyl sulfate (SDS) forms a bilayer on Te NTs. To tune the energy density performance, the Co–Fe decorated Te NTs electrode is combined with the electric double-layer capacitors (EDLC) type electrode activated carbon (AC). The asymmetric assembly shows an excellent specific capacitance of 179.2 F/g (48.7 mAh/g) at a current density of 0.9 A/g in 4 M KOH electrolyte. More importantly, it exhibits a maximum energy density of 62.1 Wh/kg at a power density of 1,138.2 W/kg under a potential window of 1.58 V. This potential finding shows the significant applicability of Te NTs as a template for the synthesis of bimetallic tellurides with unique morphologies. The synergistic effect from multiple metals and anisotropic morphology is beneficial for energy storage applications.     

A wide potential window aqueous supercapacitor based on LiMn<Subscript>2</Subscript>O<Subscript>4</Subscript>–rGO nanocomposite

Aqueous supercapacitors based on neutral solutions have the advantages of high-ionic conductivity, being environmentally friendly, safe, and low cost. However, the operating potential window for most aqueous electrolytes is far lower than that of organic electrolytes that are commonly used in commercial supercapacitors. In this work, we report on the fabrication of a wide potential window, high-energy aqueous asymmetric supercapacitor, without sacrificing power, by using a nanostructured LiMn₂O₄/reduced graphene oxide (LMO–rGO) nanocomposite. We synthesized the uniformly distributed LMO in the LMO–rGO nanocomposite using a co-precipitation route followed by a low-temperature hydrothermal treatment. In a three-electrode cell setup, the specific capacitance of the LMO–rGO nanocomposite electrode at 1 A/g (1.2 mA/cm²) is 268.75 F/g (258 mF/cm²), which shows a dramatic improvement over the sum of the specific capacitances of pristine LMO (162.5 F/g) and pure rGO (29.94 F/g) electrodes in their relative ratios, when used alone. This finding suggests a synergistic coupling of LMO and rGO in the nanocomposite. We also assembled the LMO–rGO nanocomposite, as the positive electrode, with activated carbon, as the negative electrode, into an asymmetric cell configuration. The device shows an ultra-wide potential window of 2.0 V in a neutral aqueous Li₂SO₄ electrolyte, with a maximum energy density of 29.6 Wh/kg (which approaches the commercial lead-acid batteries), power density of up to 7408 W/kg, and an excellent cycle life (5% loss after 6000 cycles). These findings confirm that an LMO–rGO nanocomposite is a promising material to meet the demands of real world energy storage.     

Electrochemical characterization of thin film electrodes toward developing a DNA transistor

The DNA-Transistor is a device designed to control the translocation of single-stranded DNA through a solid-state nanopore. Functionality of the device is enabled by three electrodes exposed to the DNA-containing electrolyte solution within the pore and the application of a dynamic electrostatic potential well between the electrodes to temporarily trap a DNA molecule. Optimizing the surface chemistry and electrochemical behavior of the device is a necessary (but by no means sufficient) step toward the development of a functional device. In particular, effects to be eliminated are (i) electrochemically induced surface alteration through corrosion or reduction of the electrode surface and (ii) formation of hydrogen or oxygen bubbles inside the pore through water decomposition. Even though our motivation is to solve problems encountered in DNA transistor technology, in this paper we report on generic surface chemistry results. We investigated a variety of electrode-electrolyte-solvent systems with respect to their capability of suppressing water decomposition and maintaining surface integrity. We employed cyclic voltammetry and long-term amperometry as electrochemical test schemes, X-ray photoelectron spectroscopy, atomic force microscopy, and scanning, as well as transmission electron microscopy as analytical tools. Characterized electrode materials include thin films of Ru, Pt, nonstoichiometric TiN, and nonstoichiometric TiN carrying a custom-developed titanium oxide layer, as well as custom-oxidized nonstoichiometric TiN coated with a monolayer of hexadecylphosphonic acid (HDPA). We used distilled water as well as aqueous solutions of poly(ethylene glycol) (PEG-300) and glycerol as solvents. One millimolar KCl was employed as electrolyte in all solutions. Our results show that the HDPA-coated custom-developed titanium oxide layer effectively passivates the underlying TiN layer, eliminating any surface alterations through corrosion or reduction within a voltage window from -2 V to +2 V. Furthermore, we demonstrated that, by coating the custom-oxidized TiN samples with HDPA and increasing the concentration of PEG-300 or glycerol in aqueous 1 mM KCl solutions, water decomposition was suppressed within the same voltage window. Water dissociation was not detected when combining custom-oxidized HDPA-coated TiN electrodes with an aqueous 1 mM KCl-glycerol solution at a glycerol concentration of at least 90%. These results are applicable to any system that requires nanoelectrodes placed in aqueous solution at voltages that can activate electrochemical processes.     

High-voltage aqueous symmetric electrochemical capacitor based on Ru0.7Sn0.3O2·nH2O electrodes in 1 M KOH

A mild hydrothermal process is applied to synthesize hydrous ruthenium–tin binary oxides (Ru_0.7Sn_0.3O₂·nH₂O) with good capacitive performance in alkaline system. Then, a symmetric electrochemical capacitor (EC) is fabricated based on the as-synthesized Ru_0.7Sn_0.3O₂·nH₂O material and 1 M KOH aqueous electrolyte. Electrochemical performance of the symmetric EC is investigated by cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy tests. Electrochemical tests demonstrate that the symmetric EC surprisingly can operate with a high upper cell voltage limit of 1.45 V in 1 M KOH electrolyte. Maximum specific capacitance and energy density of the symmetric aqueous EC are approximately 160 F/g and 21 Wh/kg, respectively, delivered at a current density of 1.25 A/g. And the specific energy density decreases to approximately 15 Wh/kg when the specific power density increases up to approximately 1,770 W/kg. The promising specific energy and power densities are obtained simultaneously for the unwonted symmetric EC due to its larger operating potential range. Moreover, the symmetric EC exhibits electrochemical stability with 85.2% of the initial capacitance over consecutive 1,000 cycle numbers.     

An electrochemical quartz crystal impedance study on the rising of an aqueous solution meniscus for a partially immersed gold electrode during the electrochemical reduction of oxygen.

An electrochemical quartz crystal impedance system (EQCIS) was used to study the resonance behavior of an AT-cut 9-MHz piezoelectric quartz crystal (PQC) with its Au electrode partially immersed in KCl, Na2SO4 and NaClO4 aqueous solutions, respectively. An in situ determination of the immersed area and the height of the electrode was achieved by simultaneous measurements of the PQC electroacoustic admittance and the electrochemical impedance. The rising of the solution meniscus for a gold electrode partially immersed in aqueous solutions was found at oxygen reduction potentials and evaluated versus the electrolyte, electrolyte concentration, solution pH and oxygen concentration. The solution meniscus rising was explained based on a lowering of the contact-angle hysteresis and a continued collection of the water product at the solid-gas-solution interface during oxygen reduction.     

Promoting operating voltage to 2.3 V by a superconcentrated aqueous electrolyte in carbon-based supercapacitor

Aqueous supercapacitors(SCs) have attracted more and more attention for their safety,fast charge/discharge capability and ultra-long life.However,the application of aqueous SCs is limited by the low working voltage due to the narrow electrochemical stability window(ESW) of wate r.Herein,we report a new "water in salt"(WIS) electrolyte by dissolving potassium bis(fluorosulfonyl) amide(KFSI) in water with an ultra-high mass molar concentration of 37 mol/kg.The highly concentrated electrolyte can achieve a wide ESW of 2.8 V.The WIS electrolyte enables a safe carbon-based symmetrical supercapacitor to operate stably at 2.3 V with an ultra-long cycle life and excellent rate performance.The energy density reaches 20.5 Wh/kg at 2300 W/kg,and the capacity retention is 83.5% after 50,000 cycles at a current density of 5 A/g.This new electrolyte will be a promising candidate for future high-voltage aqueous supercapacitors.