超级电容器炭电极材料孔结构对其性能的影响

采用无瓶颈的系列酚醛树脂活性炭为电极材料，用氮吸附和恒流充、放电，以及交流阻抗法，研究孔径和孔表面积等孔结构对其性能的影响.结果表明，活性炭电极材料双电层电容与微孔(孔宽度< 2.0 nm)表面和外孔(孔宽度 >2.0 nm)表面都有关系，但主要取决于微孔表面双电层电容.微孔表面比电容为21.4 μF•cm－2，外孔表面比电容< 10 μF•cm－2.外孔表面比电容较低可能是由于空间电荷层的影响.微孔孔径较大的炭材料具有高比电容和良好的高倍率放电的特性.     

炭化温度对烟杆基活性炭孔结构及电化学性能的影响研究

以烟杆为原料, 氢氧化钾为活化剂, 通过调节炭化温度(500～800 ℃温度范围)在相同活化条件下制备了具有不同孔隙结构的活性炭材料. N₂吸附测试表明随着炭化温度降低, 活性炭的比表面积和总孔容先增大后减小, 中孔比表面积和平均孔径却一直增大. 其中600 ℃炭化样品经KOH活化后可制得比表面积为3333 m²•g^－1, 总孔容为2.47 cm³• g^－1, 中孔孔容达2.11 cm³•g^－1的高中孔率高比表面积活性炭材料. 采用直流充放电法、交流阻抗法和循环伏安法测定上述多孔炭为电极材料的双电层电容器的电化学性能, 结果表明: 炭化温度不同的烟杆基活性炭电极均表现出良好的功率特性, 充放电流增大50倍, 容量保持率均在80%左右, 其中TS-AC-600活性炭电极在有机电解液中1 mA•cm^－2充放电时, 比电容达到190 F•g^－1. 较高的中孔率和较大的平均孔径使得烟杆基活性炭电极具有良好的高倍率充放电性能.     

聚苯胺/活性碳复合型超电容器的电化学特性

电化学电容器作为一种新型储能器件具有广泛的应用.采用(NH₄)₂S₂O₈化学氧化聚合苯胺法制备了聚苯胺电极材料，采用化学物理二次催化活化法制备了高比表面积活性碳材料.并用循环伏安、恒流充放电以及交流阻抗等方法对上述电极材料的电化学特性进行了研究.实验结果表明,所制备的聚苯胺电极材料具有高于420 F•g^－1的法拉第赝电容和良好的电化学特性，所制备的活性碳电极材料则具有160 F•g^－1的双电层电容量.分别采用聚苯胺作为正极，活性碳作为负极，38％硫酸作为电解液制备了复合型电化学电容器.复合型电容器工作电压达到1.4 V, 电容器单体比电容达到57 F•g^－1，最大比能量和最大真实比功率分别达到15.5 W•h•kg^－1和2.4 W•g^－1, 峰值比功率达到20.4 W•g^－1,电容器循环工作寿命超过500次. 与活性碳双电层电容器相比，复合型电容器还具有较低的自放电率.     

介孔SnO2的结构表征及其湿敏性能

以十六烷基三甲基溴化铵、十二胺为模板剂, 采用双模板法及均相沉淀法, 分别制备了介孔结构的SnO2. BET测试结果表明, 双模板法制备的介孔SnO2平均孔径、孔容和比表面积分别为4.9 nm、0.213 m3·g-1和172.9 m2·g-1, 而均相沉淀法合成产物孔径分布的离散程度较大, 孔容和比表面积降至双模板法的66.0%和21.8%. 以叉指电极为工作电极集电体, 利用交流阻抗技术测定了所得SnO2的湿敏性能. 结果表明, 与均相沉淀法制备的SnO2 相比, 双模板法制得SnO2的双电层电荷传递阻抗、双电层电容及Warburg扩散系数随湿度变化的幅度更明显, 表明其具有较好的湿敏性能. 对介孔结构特征与湿敏性能相关性研究表明, 具有较大孔容和比表面的介孔SnO2可改善材料的感湿性能.     

含磷活性炭作为双电层电容器电极材料的电化学性能

采用磷酸活化和磷酸改性制备了不同种类的含磷活性炭,采用元素分析、X射线光电子能谱(XPS)和氮气吸附等手段分析了活性炭的元素含量、表面化学性质和孔隙结构,采用恒电流充放电、循环伏安和交流阻抗分别考察了活性炭在KOH和H₂SO₄电解质溶液中作为超级电容器电极材料的电化学性能,采用自由截距多元线性回归拟合统计分析研究了活性炭电极比电容量的影响因素,应用三电极体系分析了磷元素对活性炭电化学性能的影响机理。研究结果表明,活性炭掺杂的磷引入了赝电容,提高了活性炭电极的比电容量,磷元素含量为5.88%(w)的活性炭的比电容量在0.1 A·g^-1下达到185 F·g^-1。统计分析结果显示,活性炭的中孔有利于电解质离子向微孔内的扩散。在6 mol·L^-1 KOH电解质溶液中,孔径在1.10-1.61 nm、2.12-2.43nm及3.94-4.37 nm范围内是电解质离子在活性炭孔隙内部形成双电层的主要场所;在1 mol·L^-1 H₂SO₄电解质溶液中,孔径在0.67-0.72 nm范围内有利于双电层电容的形成。     

双电层电容器用新型无灰煤(HyperCoal)基活性炭的制备

以无灰煤(HyperCoal)为原料,KOH和CaCO3为活化剂制备了煤基活性炭,采用低温N2吸附法表征了活性炭的比表面积和孔结构,测定了活性炭用作双电层电容器(EDLC)电极材料的电化学性能。考察了炭化温度、活化温度、活化时间和活化剂对活性炭电容特性的影响。研究结果表明,比表面积和比电容随着炭化温度的升高而降低,活化温度过高或活化时间太长对比电容有不利影响。此外,CaCO3影响活化过程中孔的开发,显著降低所制备活性炭的比表面积和比电容。在炭化温度为500℃、活化温度为800℃、KOH与焦的质量比为4∶1和活化时间2 h下所得活性炭的比表面积和总孔容分别达到2 540 m2/g和1.65 cm3/g,该活性炭电极在0.5 mol/L TEABF4/PC电解液中的比电容达到最大值46.0 F/g。     

合成路径对超级电容器用二氧化锰性质的影响

研究了不同合成路径对二氧化锰结构及电化学性能的影响. 路径1为将0.15 mol/L醋酸锰溶液加入到0.1 mol/L高锰酸钾溶液中; 路径2中, 物料的加料方式与路径1相反. X射线衍射和扫描电镜测试表明合成的产物均为无定型α-MnO2, 晶粒尺寸为200～300 nm. 氮吸附曲线测试结果表明: 路径1所得的二氧化锰具有较大的比表面积(329 m2/g), 其孔径分布比较均一, 孔径6～12 nm, 孔体积较小(0.45 cm3/g); 路径2所得的二氧化锰比表面积较小(298 m2/g), 具有从微孔到大孔的连续分布孔, 平均孔径11.4 nm, 孔体积较大(0.66 cm3/g). 交流阻抗和循环伏安电化学测试结果显示: 路径2所得样品具有较大的法拉第阻抗, 在较低扫描速度下(2 mV&#8226;s－1), 其比电容(203 F&#8226;g－1)比路径1所得MnO2高(189 F&#8226;g－1), 路径1所得二氧化锰的比电容随扫描速度变化的趋势较小. 恒流充放电测试显示路径1合成的二氧化锰具有较好的功率特性. 在2 A&#8226;g－1的电流密度下, 其比容量为0.1 A&#8226;g－1电流密度下的96.3%, 而路径1的样品的容量保持率为92.5%. 造成上述结果差异的原因是由于不同合成路径导致二氧化锰存在不同的孔结构特征所致.     

纳米MnO2超级电容器的研究

用固相合成法制备纳米MnO2，作为超级电容器材料，通过循环伏安、交流阻抗与恒电流充放电等测试手段对MnO2电极进行分析.结果表明,以1 mol•L－1 KOH为电解液， MnO2电极在－0.1～0.6 V(vs. Hg/HgO)的电压范围内具有良好的法拉第电容性能.在不同电流密度下，电极比容量达240.25到325.21 F•g－1.恒电流充放电5000次后，电极容量衰减不超过10％.     

电解液离子与炭电极双电层电容的关系

以酚醛树脂基纳米孔玻态炭(NPGC)为电极, 通过微分电容伏安曲线的测试, 研究了水相体系电解液离子与多孔炭电极双电层电容的关系. 结果表明, 稀溶液中, 多孔炭电极的微分电容曲线在零电荷点(PZC)处呈现凹点, 电容降低, 双电层电容受扩散层的影响显著；若孔径小, 离子内扩散阻力大, 电容下降更为迅速, 扩散层对双电层电容的影响增大. 而增大炭材料的孔径或电解液浓度, 可明显减弱甚至消除扩散层对电容的影响. 炭电极的单位面积微分电容高, 仅表明孔表面利用率高, 如欲获得高的电容量, 还要有大的比表面积. 离子水化对炭电极的电容产生不利影响, 选用大离子和增大炭材料的孔径, 可有效降低离子水化对炭电极电容性能的影响.     

高能量密度和功率密度炭电极材料

以核桃壳为原料, 采用同步物理-化学活化法制备活性炭(AC). 用氮气吸附法和傅立叶红外光谱(FTIR), 对活性炭的孔结构和表面官能团进行了分析. 以活性炭为电极材料制备炭电极, 6 mol·L-1 KOH溶液为电解液组装成超级电容器, 利用恒电流充放电、循环伏安、交流阻抗等电化学测试方法研究其电化学性能及其与活性炭材料结构的关系. 结果表明, 实验电容器的内电阻、漏电流小, 循环充放电稳定性好, 容量保持率高; 活性炭的比电容随比表面积的增加而增大, 且与BET比表面积呈线性相关; 孔径在1.5-4 nm之间的孔表面有利于形成有效的双电层. 中等比表面积1197 m2·g-1炭样的比电容高达292 F·g-1, 80 mA充放电时, 电容器能量密度高达7.3 Wh·kg-1, 功率密度超过770 W·kg-1,峰值功率密度为5.1 W·g-1.     

Secondary Activation of Commercial Activated Carbon and its Application in Electric Double Layer Capacitor

The cheap commercial activated carbon (AC) was improved through the secondary activation under steam in the presence of FeCl2 catalyst in the temperature range of 800-950℃ and its application in electric double layer capacitors(EDLCs) with organic electrolyte was studied. The re-acivation of AC results in the increases in both specific capacitance and high rate capability of DELCs. For AC treated under optimized conditions, its discharge specific capacitance increases up to 55.65F/g, an increase of about 33% as compared to the original AC, and the high rate capability was increased significantly.The good performances of EDLC with improved AC were correlated to the increasing mesoporous ratio.     

A review on the development of a porous carbon-based as modeling materials for electric double layer capacitors

Carbon electrodes are a key factor for electric double layer capacitors (EDLCs). Carbon gels have high porosity with a controllable pore structure by changing synthesis conditions and modifying preparation processing to improve the electrochemical performance of EDLCs. This review summarizes the preparation of carbon gels and their derivatives, the criteria to synthesize high surface area in each process, the development by some carbon forms, and EDLC applications. Porous carbons are also prepared as model materials by concentrating on how pore structure increases electrochemical capacitance, such as electronic and ion resistance, the tortuosity of pore channel, suitable micropore and mesopore sizes, and mesopore size distribution. This review emphasizes the significance of pore structures as the key factor to allow for the design of suitable pore structures that are suitable as the carbon electrode for EDLCs.     

High Power Density Electric Double Layer Capacitor with Improved Activated Carbon

Introduction　　Recently ,therehasbeenanincreasinginterestinthedevelopmentofelectricdoublelayercapacitors (EDLCs)us inghighlyporouscarbonsastheelectrodematerialsduetotheirpossibletechnologicalapplicationsasenergystoragede vicespossessinghighpowerdensitycapability .1,2 Themainadvantagesofsuchdevicesaretheirpossiblehighratecapa bilityandlongcyclelifeascomparedtorechargeablebatter ies,butitsenergydensityislowerthanthatofrechargeablebatteries.Inordertoobtaintherequiredenergyandpowerdensity,EDLC…     

Fluorination effect of activated carbon electrodes on the electrochemical performance of electric double layer capacitors

The surface of phenol-based activated carbon (AC) was fluorinated at room temperature with different F₂:N₂ gas mixtures for use as an electrode material in an electric double-layer capacitor (EDLC). The effect of surface fluorination on EDLC electrochemical performance was investigated. The specific capacitance of the fluorinated AC-based EDLC was measured in a 1 M H₂SO₄ electrolyte, in which it was observed that the specific capacitances increased from 375 and 145 F g⁻¹ to 491 and 212 F g⁻¹ with the scan rates of 2 and 50 mV s⁻¹, respectively, in comparison to those of an unfluorinated AC-based EDLC when the fluorination process was optimized via 0.2 bar partial F₂ gas pressure. This enhancement in capacitance can be attributed to the synergistic effect of increased polarization on the AC surface, specific surface area, and micro and mesopore volumes, all of which were induced by the fluorination process. The observed increase in polarization was derived from a highly electronegative fluorine functional group that emerged due to the fluorination process. The increased surface area and pore volume of the AC was derived from the physical function of the fluorine functional group.     

香菇生物质基氮掺杂微孔碳材料的制备及其在超级电容器中的应用

采用简易浸泡法和一步碳化/活化法制备香菇生物质基氮掺杂微孔碳材料(NMCs),利用扫描电子显微镜(SEM)、透射电子显微镜(SEM)、X射线衍射(XRD)和X射线光电子能谱(XPS)对材料的结构形貌进行表征,并研究了其超级电容特性。测试结果表明,NMCs的微孔比表面积高达1 594 m~2·g~(-1),且拥有更高数量的含氮官能团,其吡啶型含氮官能团比例也有所提高,展现出优异的超级电容特性。在0.5 A·g~(-1)的电流密度下,其比容量高达325 F·g~(-1),当电流密度上升到20 A·g~(-1)时,其比电容仍然高达180 F·g~(-1),表现出优异的倍率性能;同时,在5 A·g~(-1)的电流密度下,电极经历5 000次充放电循环后具有97.7%的比容量保持率,展现出优异的循环稳定性。这主要归因于NMCs超高的微孔比表面积和丰富的含氮官能团。     

Enhanced Capacitive Characteristics of Activated Carbon by Secondary Activation

The effect of the improvement of commercial activated carbon(AC) on its specific capacitance and high rate capability of double layer(dl) charging/discharging process has been studied. The improvement of AC was carried out via a secondary activation under steam in the presence of catalyst NiCl2, and the suitable condition was found to be a heat treatment at about 875 ℃ for 1 h. Under those conditions, the discharge specific capacitance of the improved AC increases up to 53. 67 F/g, showing an increase of about 25% as compared with that of as-received AC. The good rectangular-shaped voltammograms and A.C. impedance spectra prove that the high rate capability of the capacitor made of the improved AC is enhanced significantly. The capacitance resistance (RC) time constant of the capacitor containing the improved AC is 1.74 s, which is much lower than that of the one containing as-received AC(an RC value of 4. 73 s). It is noted that both kinds of AC samples show a similar specific surface area and pore size distribution, but some changes have taken place in the carbon surface groups, especially a decrease in the concentration of surface carbonyl groups after the improvement, which have been verified by means of X-photoelectron spectroscopy. Accordingly, it is suggested that the decrease in the concentration of surface carbonyl groups for the improved AC is beneficial to the organic electrolyte ion penetrating into the pores, thus leading to the increase in both the specific capacitance and high rate capability of the supercapacitor.     

Improved capacitance characteristics of electrospun ACFs by pore size control and vanadium catalyst

Nano-sized carbon fibers were prepared by using electrospinning, and their electrochemical properties were investigated as a possible electrode material for use as an electric double-layer capacitor (EDLC). To improve the electrode capacitance of EDLC, we implemented a three-step optimization. First, metal catalyst was introduced into the carbon fibers due to the excellent conductivity of metal. Vanadium pentoxide was used because it could be converted to vanadium for improved conductivity as the pore structure develops during the carbonization step. Vanadium catalyst was well dispersed in the carbon fibers, improving the capacitance of the electrode. Second, pore-size development was manipulated to obtain small mesopore sizes ranging from 2 to 5 nm. Through chemical activation, carbon fibers with controlled pore sizes were prepared with a high specific surface and pore volume, and their pore structure was investigated by using a BET apparatus. Finally, polyacrylonitrile was used as a carbon precursor to enrich for nitrogen content in the final product because nitrogen is known to improve electrode capacitance. Ultimately, the electrospun activated carbon fibers containing vanadium show improved functionality in charge/discharge, cyclic voltammetry, and specific capacitance compared with other samples because of an optimal combination of vanadium, nitrogen, and fixed pore structures.     

活性炭二次活化对其电化学容量的影响

为进一步提高作为电化学超级电容器电极材料活性炭的电化学容量, 采用KOH作为二次活性剂, 将所得活性炭进行二次化学活化处理, 从而得到二次活化活性炭. 将原始活性炭材料与二次活化活性炭材料都分别经过系列处理, 组装成电化学超级电容器进行电化学性能测试. 测试结果表明, 二次活化活性炭材料的电化学容量达到145.0 F·g-1(有机电解液), 远远大于原活性炭材料的容量(45.0 F·g-1). 为研究二次活化活性炭材料电化学容量大幅提高的原因, 将这两种材料分别进行微观结构数据测试, 包括比表面积、N2吸脱附等温曲线和孔径分布. 研究结果表明, 二次活化处理大大增加了二次活化活性炭材料在孔径为2-3 nm的中孔分布, 从而证实对于有机电解液, 电极材料在2-3 nm的中孔对其电化学容量的提高具有重要意义.