【作者】 杨静；

【导师】 胡中华；

【作者基本信息】 同济大学 ， 物理化学， 2008， 硕士

【摘要】 电化学电容器（Electrichemical capacitor）,也称为超级电容器（Supercapcitor）,是一种介于普通电容器和二次电池之间的新型储能器件,在国防和民用领域有广泛的应用。电极是决定超级电容器性能的主要因素,因而高性能电极材料的研究一直是该领域的热点。炭材料来源广泛,价格低廉,性能稳定,易产业化,是一种相对理想的电极材料,因而同时受到了学术界和工业界的极大关注。本课题的目的是制备高性能的活性炭电极材料,并应用于超级电容器,研究炭材料性质与超级电容器性能的相关性。用自动氮吸附法研究了炭材料的比表面积、孔径和孔径分布,用循环伏安、恒电流充放电、交流阻抗等电化学方法研究了炭电极电容器的比容量、循环充放电、内电阻、漏电流等性能。本论文主要做了以下几方面的工作:以废弃核桃壳为原材料,采用ZnCl₂-CO₂同步物理-化学活化法制备活性炭（AC）。根据炭样品在77K时的氮吸附-脱附等温线,用BET方程、t-图和BJH法分析和计算比表面积和孔径、孔径分布等。并通过设计正交实验和单因素实验深入讨论了活性炭制备过程中,化学活化剂比例,活化温度,活化时间,气体流量等因素对材料孔结构的影响,并对活化条件做了优化,以制备出高性能的超级电容器用活性炭电极材料。结果显示,活化剂比例与活化温度是影响活性炭材料比表面积和孔结构参数的主要因素,通过优化活化条件,制备了比表面积和孔容分别高达2266 m²/g,1.4169 cm³/g的活性炭,以及中等比表面积（1206m²/g）,平均孔径高达2.73 nm的活性炭电极材料。用自制和商品活性炭制作电极,以KOH溶液为电解液,并组装构成双电极三明治型双电层电容器,通过恒流充放电、循环伏安等电化学研究,发现材料的孔结构,特别是孔径分布范围对电容器的性能有决定性作用,对于无机水系电解质KOH溶液,炭材料分布于1.5-4 nm的孔表面更有利于形成双电层;炭表面官能团能改善孔道的润湿性以及提供部分赝电容,从而提高电容器的电容量:平均孔径为2 nm左右的活性炭材料,其质量比电容与微孔表面积或BET表面积有很好的线性关系。与商品炭对比,自制活性性炭表面积利用率高,电化学性能优异。5 mA恒流充放电时,比电容高达292 F/g,80 mA时仍然保持在近210 F/g。电容器电阻和漏电流小,分别只有0.57Ω和0.19 mA;电容器能量密度、功率密度和峰值功率密度可分别高达7.3 Wh/kg,770 W/kg和5.1 W/g;经1000次循环恒流充放电后,容量保持率为90%以上。以活性炭为主体,利用溶胶-凝胶法制备NiO_x干凝胶/活性炭复合电极材料,孔结构分析、X射线衍射（XRD）、热重分析（TGA）等方法研究复合炭材料的性质,并测试相应的电化学性能。结果显示复合电极材料较原样炭的电化学性能有较大的改善。不同活化温度复合电极材料电化学性能测试显示,活化温度为320℃时,Ni（OH）₂凝胶分解生成混合价态的NiO_x干凝胶,复合电极材料比电容值最高达235.2 F/g,比原炭样提高了87.4%。体积比电容由原炭样的77.6F/cm³提高到140.2 F/cm³,提高了80.1%。结果显示,活化后的复合炭电极材料电化学性能稳定,循环伏安,交流阻抗和漏电流等性能都要优于原活性炭。为了提高功率密度和能量密度,用有机电解液代替KOH溶液,试制、研究了有机电解液超级电容器。自制的活性炭电极材料在有机电解液Et₄NBF₄/PC（四氟硼酸四乙基铵/碳酸丙烯酯）中表现出良好的充放电性能以及其它电化学性能。比电容可达182 F/g;能量密高达39.5 Wh/kg;最高功率为2583.5 W/kg。更多还原

【Abstract】 Supercapacitor,also named as electrichemical capacitor,is a new kind of energy storage device in-between conventional capacitor and second battery.It has been widely applied in military and electronic products or equipments.The electrode is an important component influencing the performance of supercapacitor.Therefore,the research on high performance electrode materials has been hot topic in this filed. Carbon electrode materials have attracted great attention to academe and industry, because of their abundant sources,commercial available,low price,excellently physical and chemical stability and feasibility of manufacture.The purpose of this study is to prepare low cost and high performance carbon electrode material for supercapacitor and to study the relation between carbon property and performance of the carbon electrode base supercapacitor.The nitrogen adsorption was used to study the specific surface area,pore volume,average pore diameter and pore size distributions.The properties of supercapacitors,such as specific capacity,equivalent series resistance（ESR）,leakage current were studied by electrochemical methods of cyclic-voltammetry,constant current charge/discharge, alternating current impedance etc.Main investigations and achievements were discribed as following:Activated carbon samples were prepared by means of simultaneous ZnCl₂-CO₂ physical-chemical activation using walnut shell as precursor.The specific surface area,pore size distribution was studied according to the nitrogen adsorprion-desorption isotherms by using BET model,t-plot and BJH method.The influence of ZnCl₂/shell ratio,activation temperature,activation time and CO₂ gas flow on the specific surface area and porosity parameters of activated carbon was studied through designed orthogonal experiments.The resurt showed that ZnCl₂/shell ratio and activation temperature are two key factors influencing the porosity of activated carbon.By optimizing activation conditions,the specific surface area and pore volume of resultant AC could be as high as 2266 m²/g,1.4169 cm³/g;and the average pore size of another sample could reach to 2.73 nm with a medium specific surface area of 1206 m²/g.The sandiwich-type supercapacitors were assembled with resultant carbon electrodes and electrolyte of 6 mol/L KOH solution.Their electrochemical properties were investigated by charge-discharge of constant current,cyclic voltammogram etc. The results demonstrated that pore structure,especially the pore size distribution had a significant inference on the performance of supercapacitors.For KOH electrolyte solution,the pore size distribution in the range of 1.5 nm-4 nm is favorable to the formation of electric double layer on the carbon surface.And the surface functional groups can improve the wettability and generate pseudocapacitance,so that enhanced the specific capacitance of carbon electrode.The specific capacitance increased proportional with increasing microporous and BET surface area of AC with an advange pore size arround 2 nm.Compared with a commerical AC,the resultan ACs prepared showed higher ratio of effective surface area for the formation of electric double layer and better electrochemical performance.The specific capacitance could be as high as 292 F/g at 5 mA change/discharge current;and retained a high value of 210 F/g at 80 mA.The resistance and leakage current of the capacitor are 0.57Ωand 0.19 mA,respectively; the energy density,power density and maximum power of capacitor were 7.3 Wh/kg, 770 W/kg and 5.1 W/g,respectively.The capacitance maintained above 90%after 1000-cycle charge-discharge.NiO_x/AC composite electrode materials were prepared by means of sol-gel method and characterized by the nitrogen adsorption,XRD,TGA.And the performance of electrode of composite material was also tested.The results showed that the performance and specific capacitance of the composite electrode were improved compared to the blank AC.The composite materials were thermally treated at different temperature.The result showed that the specific capacitance of composite material treated at 320℃could be as high as 235.2 F/g,87.4%higher than of original carbon.The corresponding volume specific capacity is 131.3F/cm³, 80.1%higher than of original carbon.The capacitors with composite carbon electrodes exhibited much better performance in terms of electrochemical stability, cyclic voltammogram,charge-discharge,impedence spectrum and leakage current.In order to increase the energy and power density,the organic electrolyte Et₄NBF₄/PC instead of KOH solution was used in the carbon-based supercapacitors. The specific capacitance of a lab-made mesoporous carbon sample was 182 F/g at the discharge current of 5 mA;the corresponding energy density attain to 39.5Wh/kg. The highest power density could be 2583.5W/kg.更多还原