磺化沥青基二维多孔碳纳米片的构建及其在高性能EDLCs中的应用

Electric double-layer capacitors (EDLCs) have broad application prospects in the field of urban rail transit system. However, nanoporous carbon materials cannot maintain high electrochemical characteristics throughout the whole life cycle, severely hindering the practical application. Particularly, sulfonated pitch (with polyaromatic hydrocarbons) carbon precursor are dispersed in an alkaline solution to obtain the nano-sized graphene oxide-like primary structure, which can be constructed into the secondary structure (micron-sized graphene oxide-like self-assembly aggregates) by interface self-assembly method. Herein, two-dimensional pitch-based porous carbon nanosheets (PCNs) are synthesized from the secondary structure by capillary evaporation densification and KOH chemical activation. Based on the as-obtained material, EDLCs are constructed with excellent rate capacity and high volumetric energy density. Firstly, with the purpose of constructing two-dimensional materials, different kinds of surfactants are to be introduced into the primary structure to acquire the oriented aromatic layer, so as to clarify the formation mechanism of the secondary structure. Secondly, for the sake of balancing the electronic conduction network and ion transport network, efforts are made to investigate the structural evolution mechanism of secondary structure in the KOH activation process, in order to elucidate its influence on the electronic conductivity and specific surface area of PCNs. Thirdly, aiming at improving the volumetric energy density of EDLCs, the stacking density of PCNs is effectively affected by the capillary evaporation densification strategy. Finally, exploration is conducted on the scientific relationship between the structure parameters and electrochemical performance of PCNs, to illuminate the crucial factors determining the electrochemical properties of EDLCs in the whole life span.

双电层电容器（EDLCs）在城市轨道交通系统中有广泛的应用前景，但现有纳米多孔碳材料难以在全生命周期中均维持好的电化学储能特性。本项目提出以富含稠环芳烃的磺化沥青为碳源，在碱溶液中分散得到纳米级“类氧化石墨烯”一级结构单元，采用界面自组装手段可控构建微米级“类氧化石墨烯自组装聚集体”二级结构单元，最终经致密化和KOH活化处理得到二维沥青基多孔碳纳米片，并组装成具有大倍率和高体积能量密度的EDLCs。以构建二维材料为目标，通过引入不同的表面活性剂对一级结构单元的芳香片层进行取向调整，明确二级结构单元的形成机理；以均衡电子&离子传输网络为目标，研究二级结构单元在KOH活化过程中的结构演变机制；以构建高体积能量密度的EDLCs为目标，探究毛细蒸发致密化手段对材料的大中孔和大孔的调变机制；从机理上阐述材料的结构参数与电化学特性之间的科学联系，阐明影响EDLCs全寿命周期中电化学性能的关键因素。

双电层电容器(EDLCs)的体积能量密度较低，本项目围绕合理平衡多孔碳材料的堆积密度和孔结构开展了一系列的研究工作。以低成本的工业副产品磺化沥青（SP）为碳源，利用不同类型的表面活性剂对SP进行界面自组装，经过KOH活化可控合成兼具高堆积密度和优良孔结构的2D多孔碳纳米片，在用作EDLCs电极时可获得高的体积能量密度和稳定的循环寿命。内容主要包括：采用SP为碳前驱体，引入P123表面活性剂对“类氧化石墨烯”一级结构单元进行取向调整，后经高温活化制备得到了高碳收率的二维多孔碳纳米片，可兼顾高的电导率和优良的机械柔韧性；通过界面自组装和简单的活化退火工艺有效降低多孔碳材料的含氧官能团数量，构建出高耐电压（>2.7 V）的二维多孔碳骨架，在离子液体中3.5 V高电压下具备优异的电化学性能；通过简单的水热反应和致密化手段合成了具有高堆积密度的二维致密多孔碳纳米片，兼具高的比表面积和高的导电率；以生物质腐殖酸为碳前驱体，通过离子型表面活性剂CTAB的诱导自组装和KOH活化工艺制得超低含氧基团的三维分层多孔碳，有效提升了材料的耐电压性能；通过CTAB诱导的界面自组装和KOH活化工艺合成了蜂窝状多孔碳，其具有合理的孔径分布，在离子系电解液中表现出优异的倍率性能和高的体积能量密度（39 Wh L-1）。本项目深入探讨了SP中纳米级“类氧化石墨烯”一级结构单元的结构；以构建 2D 材料为目标，通过引入不同的表面活性剂与一级结构单元进行自组装可控构建二级结构单元；深入研究高温 KOH活化和致密化手段对2D多孔碳纳米片的比表面积和孔结构的影响；从机理上阐述材料的结构参数与电化学性能之间的科学联系，为多孔碳材料研究领域中的结构设计和功能化调控提供理论依据。