【作者】 夏笑虹；

【导师】 刘洪波；

【作者基本信息】 湖南大学 ， 材料科学与工程， 2012， 博士

【摘要】 本文以酚醛树脂为炭前驱体原料，分别采用化学活化法、溶胶-凝胶炭化法、软模板法和聚合物共聚炭化法制备双电层电容器（EDLC）电极用高比表面积和适宜孔径分布的多孔炭材料。重点考察了上述制备方法及其工艺条件对多孔炭材料孔隙结构与电化学性能的影响，探讨了各制备方法中炭材料孔隙的成孔机理，阐明了多孔炭材料的电化学性能与其比表面积和孔结构之间的关系，确立了调控高比表面积多孔炭孔结构的工艺方法及工艺条件，为多孔炭材料孔结构的调控提供了实验和理论依据，有助于进一步提高多孔炭材料作为EDLC电极材料时的电化学性能。以酚醛树脂为炭前驱体，KOH作活化剂，采用炭化-活化两步法制备了EDLC用多孔炭材料。系统考察了碱炭比、炭化温度和活化时间等工艺因素对多孔炭收率、孔结构和电化学性能的影响。探讨了多孔炭孔隙结构与电化学性能之间的关系，确立了适合不同电解液体系用多孔炭电极材料的制备工艺方法和条件。研究表明，碱炭比、炭化温度和活化时间对多孔炭的孔隙结构均有较大影响，通过调节炭化温度可在较低活化剂用量下调控多孔炭材料孔隙结构。在炭化温度为600℃、碱炭比为3、活化温度为900℃和活化时间为2h的工艺条件下，可制得比表面积为2918.6m~2/g，总孔容为1.41cm3/g，其中微孔比表面积为2628.3m~2/g，中孔率为19%的多孔炭材料（PF-600），该多孔炭在水系电解液中1mA/cm~2充放电时，比电容达到310F/g，电流密度增大50倍容量保持率达到90%；在其它工艺参数相同的条件下，炭化温度降低至550℃时制得的多孔炭材料（PF-550）的比表面积为2983.5m~2/g，总孔容为1.58cm3/g，其中微孔比表面积为2269.4m~2/g，中孔率增大到37%。在有机电解液中1mA/cm~2充放电时，比电容达到160F/g，电流密度增大50倍容量保持率达到82%，显示出良好的功率特性。对于有机电解液体系，多孔炭材料中存在适当比例的中孔不仅可以改善电极材料的功率特性，而且能提高微孔的利用率。以间苯二酚和甲醛为原料、六亚甲基四胺（HMTA）为催化交联剂，醇类为溶剂，经溶胶-凝胶、常压干燥和炭化处理成功制备出高比表面积且富含中孔的炭气凝胶。系统考察了溶剂类型、聚合反应温度和炭化升温速率等工艺因素对炭气凝胶孔隙结构和电化学性能的影响。确立了制备EDLC电极用炭气凝胶的工艺方法和工艺条件。研究结果表明，选用具有催化交联双重作用的HMTA作催化剂以及表面张力和挥发速度适宜的乙醇作溶剂可以实现RF湿凝胶的常压干燥，所得干凝胶能较好地保留溶胶-凝胶过程中形成的网络结构，进一步炭化后可制得富含中孔的多孔炭气凝胶。通过改变溶剂类型、缩聚反应温度和炭化升温速率等可有效调控多孔炭气凝胶的孔隙结构。随着缩聚反应温度的升高，炭气凝胶的中孔孔径不断增大，中孔含量增多；随着炭化升温速率的加快，炭气凝胶的比表面积呈先增大后减小的趋势，而中孔率则先减小后增大。在间苯二酚（R）/甲醛（F）摩尔比值为2.0，R/六亚甲基四胺（H）摩尔比值为50，乙醇（S）为溶剂且R/S为0.1g/ml，80℃下反应72h，常压干燥后以2℃/min的升温速率升温至900℃炭化，制得的多孔炭气凝胶的比表面积为739.0m~2/g，中孔率达到50%，平均孔径为2.76nm。该炭气凝胶电极在水系电解液中1mA/cm~2电流密度下的比电容达180F/g；电流密度增大50倍，容量保持率达到86%，表现出良好的高容量、高功率特性。以间苯二酚（R）和甲醛（F）为原料，分别采用六亚甲基四胺（HMTA）和盐酸（HCl）作催化剂，通过添加嵌段共聚物F127作致孔剂，利用协同自组装和炭化处理制备了具有规整孔隙结构的多孔炭材料。分析了F127加入量对所得多孔炭材料的形貌、孔隙结构和电化学性能的影响，探讨了多孔炭材料的孔结构形成机理，确立了制备具有规整孔隙结构多孔炭材料的工艺方法和工艺条件。研究表明催化剂类型对树脂复合体系的结构有较大影响，且进一步影响所得多孔炭材料的孔隙结构。采用弱碱性的HMTA作催化剂时，由于催化效率低，间苯二酚与甲醛的溶胶-凝胶过程时间较长，需溶剂缓慢挥发才能形成较为有序的嵌段共聚物与酚醛树脂的复合中间相结构，反应过程中容易发生单轴结构变形，导致最终得到的多孔炭材料孔隙结构的有序性难以保证。采用强酸性的HCl作催化剂时，由于酚醛树脂和嵌段共聚物F127被部分质子化，反应体系可以在库伦引力（I+X-S+机理）和氢键（I0S0机理）的共同作用下自组装形成纳米复合体系，纳米复合体系微相结构的有序性提高，同时保证较高的合成速率，进而获得具有有序孔道分布的多孔炭材料。采用HCl作催化剂时，不同F127加入量制得的多孔炭材料比表面积达到645~701m~2/g，总孔容为0.41~0.55cm3/g，平均孔径在2.46~3.38nm之间。其中当R/F为2.0（摩尔比），F127/R为1.3（质量比），900℃下炭化制得的多孔炭比表面积为701.2m~2/g，中孔孔容为0.36m3/g，中孔率达到67.0%。该多孔炭电极在水系电解液中1mA/cm~2电流密度下的比电容为165F/g，电流密度增大50倍，容量保持率高达93%。经过5000次循环，容量保持率达94%以上，具有良好的大电流充放电性能和循环性能。以酚醛树脂（Phenolic resin, PF）为炭前驱体，分别以小分子二元酸（己二酸（HA）和辛二酸（SA））和环氧预聚物（QS）为致孔链段，首次以聚合物共聚炭化法制备出孔隙结构丰富的多孔炭材料，实现了以聚合物共聚炭化法制备多孔炭材料的设想。考察了致孔链段加入量对多孔炭孔隙结构和电化学性能的影响。探讨了聚合物共聚体系炭化制备多孔炭材料的孔结构形成机理。研究结果表明二元酸通过分子链两端的羧基与酚醛树脂中的羟甲基发生酯化反应，一定量的二元酸以链段或接枝的形式接入到酚醛树脂固化物中，其热解温度由150~230℃提高至400~450℃，即能够在PF已初具骨架强度时再热解。其中，HA加入量为25%时所得多孔炭的比表面积和总孔容分别达到550.9m~2/g和0.27cm3/g，在水系电解液中电流密度为1mA/cm~2的质量比电容为145F/g。以QS为致孔链段，利用QS中的端环氧基与酚醛树脂中的酚羟基发生反应生成醚键使QS接枝到酚醛树脂的链段上，该共聚体系进一步炭化后可制得孔隙丰富的多孔炭材料。随着QS用量的增加，多孔炭的比表面积先增大后减小，在QS加入量为15%时达到最大值609.0m~2/g，总孔容为0.28cm3/g，在水系电解液中1mA/cm~2的电流密度下的比电容量为177.5F/g，电流密度增大50倍，容量保持率为76%，具有较高的容量保持率。聚合物共聚炭化法中，共聚体系在固化反应完全后，体系中嵌段或接枝链段形成的微相区由于化学键连接和较强的分子间力的作用，相分离受到抑制，相结构粗化被延迟，即相区尺寸被控制在纳米尺度范围内。该复合结构在升温炭化时，由于致孔化合物所形成的微相区热解，在炭前驱体当中形成孔隙，且孔隙大小相较于共聚体系中的微相区域尺寸有所收缩，同时由于致孔化合物通过化学键与固化体系相连接，在炭化过程中，能在树脂炭化体系初具骨架强度时再热解，使得由其热解而产生的孔隙不因树脂固化体系网络结构的收缩塌陷而消失。最终获得孔隙丰富的多孔炭材料。所提出的共聚物炭化法工艺简单，孔隙结构可控且环境友好，有良好的应用前景。更多还原

【Abstract】 Porous carbons with high specific surface area and reasonable pore sizedistribution used for electric double layer capacitor (EDLC) were prepared with resolphenolic resin as raw material by different methods, including chemical activation,sol-gel polymerization, soft-template and polymer blend technique. The influences ofpreparation method and conditions on structure and performance of porous carbonswere thoroughly investigated and the pore-forming mechanisms were discussed. Therelationship between the electrochemical performance of porous carbon and porestructures were clarified. Based on these, the technologic methods and conditions ofcontrolling the pore structures of porous carbon were established, which wouldprovide theoretical basis and experimental supports for further improving theperformance of porous carbon in EDLC.High specific surface area porous carbon with distinct pore structure wasprepared with resol phenolic resin as raw material and KOH as activator by chemicalactivation. The influences of the active agent amount, carbonization temperature andactivation time on yield, pore structure and electrochemical performance of porouscarbon were investigated. The relationship between the pore structure and capacitancewas analyzed and the preparation conditions were established of porous carbonsuitable for different electrolytes.The results show that the active agent amount, carbonization temperature andactivation time have great effect on the pore structure of porous carbon. By controllingcarbonization temperature, the pore structure can be easily adjusted at relative lowcontent of active agent. The pore volume and mesoporosity of porous carbonsincreased with decrease of carbonization temperature, while the BET surface areaincreased firstly and decreased afterwards. The surface area total, pore volume,micropore surface area and mesoporosity of PF-600reach2918.6m~2/g,1.41cm3/g,2628.3m~2/g and19%, respectively. As carbonization temperature decreasing to550℃,the values of PF-550are2983.5m~2/g,1.58cm3/g and2269.4m~2/g and themesoporosity was enhanced to37%. PF-600exhibited the best electrochemicalperformances in30%KOH electrolyte that the specific capacitance value reached310F/g at1mA/cm~2and retained as90%even when the current density was enlarged50times. While the specific capacitance value of PF-550reached the highest value of160F/g in1M Et4NBF4/AN electrolyte and retained82%at50mA/cm~2. It is widelybelieved that to obtain high capacitance and rate performance at the same time especially in organic electrolyte, porous carbon with a high specific surface area and alarge amount of mesopores is effective.Carbon aerogel with high specific surface area and developed mesopore structurewas successfully prepared via a sol-gel process from the polycondensation ofresorcinol and formaldehyde catalyzed by HMTA in alcohol-solvent, followed bydrying at ambient pressure and pyrolysis at900℃under inert atmosphere. The effectsof solvent types, polymerization temperature and carbonization heating rates on thepore structure and capacitance performance were studied systematically. And thetechnologic conditions of preparing carbon aroegels were established.The results show that by employing hexamethylenetetramine (HMTA) as both acatalyst and curing agent and ethanol as solvent, ambient drying of carbon aerogelscan be realized. The network formed in sol-gel polymerization can be ideally keptafter ambient dry and porous carbon with developed mesopores was accordinglyobtained.The pore structure of carbon aerogel could be controlled by changing solventtype, polymerization temperature and carbonization heating rates. The amount andsize of mesopores in carbon aerogel increase with polymerization temperature.Meanwhile, the specific surface area increase first and then decrease with fastercarbonization heating rates, but mesoporesity changed adversely. The best technologicconditions of sol-gel method are the R/F, R/H mole ratio, R/S value, thepolymerization temperature and carbonization heating rates being2.0,50and0.1g/ml,80℃and2℃/min, respectively. The highest specific surface area, mesoporosity andaverage pore diameter of carbon aerogel are739.0m~2/g,51%and2.76nm,respectively, which exhibit the highest capacitance of180F/g at1mA/cm~2and thebest high current charge/discharge performance, retaining86%even at50mA/cm~2.With resorcinol(R), formaldehyde (F) as raw materials, hexamethylenetetramine(HMTA) and hydrochloric acid (HCl) as catalyst, porous carbon material with tailoredpore structure, high specific surface area of701.2m~2/g and developed mesoporosity of67.0%was obtained by self-assembly method of block copolymer F127as the porogenand followed by carbonization. The influence of the content of F127at differentcatalysts on the surface appearance, pore structure and electrochemical performance ofporous carbon were researched. Meanwhile, the pore forming mechanism wasdiscussed.The results show that different catalyst system have great influence on structure ofphenolic resin based composite and further affect pore structure of porous carbon obtained when using block copolymer as thermal decomposable polymer. When weakbasic catalyst HMTA was used, the sol-gel process of resorcinol and formaldehydeproceeded tardily and a single-shaft distortion easily occurred. The ordered porestructure of porous carbon can be hardly guaranteed and the synthesis efficiency wasalso low. The phenolic resin and block copolymer (F127) were partly protonized whenstrong acid (HCl) was used. The reacting system can assemble into a nanometercompound system under both Kulun attraction (I+X-S+mechanism) and the hydrogenbond (the I0S0mechanism). The regularity of composite can be enhanced and thesynthesis speed increased simultaneously. Accordingly, porous carbon with regularpore distribution was obtained.The specific surface area, total pore volume, and average pore size of porouscarbon materials with different F127ratio at HCl catalyst are between640~700m~2/g,0.41~0.55cm3/g and2.46~3.38nm, respectively. When F127/R is1.3, the specificsurface area and mesopore volume of porous carbon is701m~2/g and0.36m3/g,respectively. The mesoporosity achieved67.0%. The capacity maintenance reached ashigh as93%as the current density increases50times and kept94%after cycling5000times.Porous carbons with specific surface area of609m~2/g and mesopore sizecentralized in3~4nm were prepared firstly by chemical blending of phenolic resin(PF) with adipic diacid (hexanedioic acid (HA) and suberic acid (SA)) andepoxy-terminated prepolymer (QS). The influences of the content of pore formationagent to PF on pore structure and capacity performance were investigated. Themechanism of pore formation in chemical blending was also discussed. The methodprovides an ideal experimental carrier for studying pore formation and the correlationwith electrochemical performance.Chemical reaction of PF with diacid is manifested by a shift of carbonylstretching peak of diacid to a higher frequency in FT-IR spectra and a higherdecomposition temperature from150~230℃to400~450℃of diacid in TG curves.Namely, the thermal decomposition didn’t occur until a relative steady skeleton ofphenolic resin has been established. This may be the main reason of the pore-formingability of diacid molecules. The specific surface area and mesopore volume of porouscarbon is550.9m~2/g and0.27m3/g, respectively, as the content of HA is25%. Thespecific capacity of the carbon is145F/g.Porous carbons were prepared by chemical blending of phenolic resin (PF) andepoxy-terminated prepolymer (QS). During the curing reaction, epoxy groups of QS reacts with the phenolic hydroxyl of PF to form ether linkage. The specific surfacearea, total pore volume and micropore volume increase with the ratio of QS to PF atfirst and then decrease, reach the maximum at the value of w(QS)/w(PF)=15%, whichare609.0m~2/g,0.28cm3/g and0.22cm3/g, respectively. When the porous carbon usedfor the electrodes of electrochemical double layer capacitor (EDLC), a satisfiedspecific capacitances of177.5F/g in30wt%KOH aqueous electrolytes is acquiredand the capacitance maintenance achieve76%as the current density enlarged50times.After curing reaction, the microphase separation formed by block or graft chainsin copolymers was restricted and the enlarging of microphase structure was delayedbecause of chemical bonding and molecular interaction between block or graft chainsand carbon precursor. The region of microphase structure was confined in nanometerscale. The pore will come into being after pyrolysis of the block or graft chains andsmaller than the size of the microphase structure existed before. Meanwhile, thethermal decomposition of graft chains didn’t occur until a relative steady skeleton ofphenolic resin has been established, so the pores didn’t disappear with the shrinkageof copolymers. This method has a very good application prospect in preparation ofporous carbon for electric double layer capacitor because of its simple process, porestructure controllable and environmental friendliness.更多还原