【作者】 王瑨；

【导师】 王成扬；

【作者基本信息】 天津大学 ， 化学工艺， 2010， 博士

【摘要】 两亲性炭材料(ACM)是一种在保持沥青、生焦等前躯体固有优点的同时,还兼备了水溶性,富官能团性,热固性等优点的碳质材料。ACM在制备炭材料过程中可以避免有机溶剂的使用,降低化学试剂用量,省去氧化稳定化过程,具有经济,节能,环保的特点,符合绿色化工的要求。考察ACM的结构,形成机理,拓展其在储能领域的应用,具有一定的科研价值与应用前景。本文结合多种表征手段对ACM的形成机理与结构特点进行了分析。分析表明,在混酸处理NC的过程中,会在分子的侧链、杂环或者边缘处发生氧化、硝化、磺化等一系列反应,引入-OH、-COOH、-NO2、-SO3H等官能团,此过程中主要发生了分子的官能团化和稠环分子的剥离,而稠环本身并未被严重破坏。ACM分子中富含官能团的部分成为亲水端,官能团含量少的部分成为亲油端。当ACM浓度过大时,分子间能通过有效碰撞形成一些胶束,进而形成凝胶,甚至是冻胶。通过溶剂置换法得到了具有同心圆结构的ACM纳米球,这种微球从侧面证明了ACM在水中是以纳米尺寸分散的。材料在热处理过程中保持了良好的热固性,这是由于在ACM制备过程中,分子的侧链、杂环或者边缘处发生了化学反应,使得ACM分子C/H比增加,支链多被氧化,热塑性变差。以二甲基硅油为分散介质,ACM水溶液为分散相,采用溶剂挥发法宏量制得ACM微米球。石墨化后的ACM基炭微球作为锂离子电池负极材料具有较高的容量(340mAh/g)与首次效率(90%),并表现出优良的倍率放电性能。由于ACM的两亲性,ACM分子可以在水/石墨界面生成一层自组装包覆层,将人造石墨的边缘与缺陷包覆起来,形成核-壳复合材料。ACM的用量对复合材料的性能有着重要的影响。用量过少不能形成完整的包覆层,用量过大会导致材料结块,破碎过程中破坏核-壳结构。采用少量多次包覆可以有效克服这一矛盾。理想的包覆能形成均匀、完整的包覆层,使材料堆积密度增高,比表面积降低。与原料人造石墨相比,复合材料的首次效率有所提高,不可逆容量降低,并且拥有良好的循环稳定性。以ACM为前躯体在低KOH用量下可以得到同时具有高比表面积和一定中孔含量的活性炭,这是由于ACM能够在KOH溶液中均匀分散,并具有丰富的反应活化能较低的杂原子,以及较大的层间距,使得化学活化更为均匀而有效。通过调整碱炭比、活化温度和活化时间等参数,可以实现对活性炭孔结构的控制。在电化学测试中,ACM基活性炭展现出良好的双电层电容器特性和循环稳定性。更多还原

【Abstract】 Amphiphilic carbonaceous material (ACM), a material with high carbon content, economic cost, low volatile and ash content as pitch or coke, is soluble in alkaline aqueous solution, plenty in functional groups, and thermohardening. Based on these properties, no organic solvent and stabilization process is needed during the thereof carbon materials preparation from ACM. Therefore, ACM is economic, facile, and green in carbon materials production. It is necessary to study the structure of ACM and develop its applications in energy storage.In this paper, structure of ACM was studied via various characterization methods. It is confirmed that O, N, and S atoms were introduced into ACM by a series of combinated reactions including carboxylation, nitration and sulfonation during the nitro-sulfuric acid treatment. Such kinds of acidic functional groups are hydrophilic and tend to react with alkalis. Thus, it is all those hydrophilic groups that cause ACM to be soluble in alkali aqueous solution. During the oxidation, the links between adjacent graphitic microcrystallines in NC was forcibly broken. However, the graphene sheets composed of small hexagonal carbon rings are too stable to be destruction. As the concentration increase of ACM, gel was formed by the molecular movement and graft. In this paper, ACM-based nano-spheres were synthesized in aqueous solution. This, from another point of view, could demonstrate ACM could disperse in water in nano size with the help of hydrophilic functional groups.ACM shows well thermosetting property during heat treatment. This is because the side chain of NC were oxidized, nitrified or sulfonated during the ACM preparation, which reduced the thermoplasticity of material. In this work, we report the preparation of well-controlled ACM-based spheres by solvent evaporation method with polydimethylsiloxane as the continuous phase. The graphitized microspheres were then tested as anode material and showed satisfactory electrochemical behaviors with large capacity (340mAh/g), high initial efficiency (90%), and good rate capability.Artificial graphite powder was coated by ACM in aqueous solutions. Results show that surface defects and edge sites of original graphite were uniformly covered by ACM coating layer after modification, while the overall characteristics of graphite were not severely changed. After modification, the bulk density of material increased while its surface area decreased. Electrochemical measurements were then carried out to evaluate the anode performances of samples in lithium-ion batteries. The composite showed higher initial efficiency, lower inreversible capacitance, and better cyclic performance than raw artificial graphite.As a special precursor with small particle size, plenty of functional groups and widened d002 simultaneously, ACM guarantees subsequent ACM-based activated carbons (AACs) with high specific surface area as well as well-developed mesoporous structure after KOH activation. The modification of pore structure or achieved by controlling the activation conditions including KOH/ACM weight ratio, activation temperature and maintain time. In electrochemical measuraments, all AAC samples exhibited high performances as electrode materials for electric double-layer capacitors.更多还原