基于环糊精支化聚合物的多孔碳制备及其超电容储能机理研究

Supercapacitor is an electrochemical energy storage device that possesses both high power density and excellent cyclic stability. The key to increase the energy density of supercapacitors is to improve the performance of the electrode materials. Porous carbon materials have been extensively used in commercial supercapacitors but there is still great potential for improvement of their capacitive performance. To this end, it is important to understand deeply the interaction between electrolytes and different types of pores and to tune the pore structure effectively. In this project, porous branched polymers will be constructed by cross linking reaction and using cyclodextrin (CD) as the branching unit. The polymer will be carbonized through which the bridging units are sacrificed and the CD units are converted into carbon microcrystallites at the branching points, resulting in novel three-dimensional porous carbons. The porosity of the CD polymers and the pore structure of the resultant carbons will be precisely tuned by changing the rigidity, length and branching degree of the molecular chains for the cross-linking agents. The as-synthesized porous carbons will be used as electrodes to fabricate high-performance supercapacitors. Furthermore, solid nuclear magnetic resonance will be used to study the electrostatic adsorption process of electrolytes in micropores and small mesopores and to elaborate the relationship between the pore structure and the capacitive performance. These work would provide theories and fundamental data, and consequently to imperove the performance and foster the industrial applications of carbon materials for energy storage.

超级电容器是一种兼具高功率密度与良好循环稳定性的电化学储能装置，提高其能量密度的关键在于改善电极材料的性能。多孔碳材料已经被广泛应用于商业超级电容，然而其电容性能仍然有巨大的提升空间，深刻理解电解质与各类型孔的相互作用并有效调控孔结构对于提升性能至关重要。本项目拟采用环糊精为支化点、通过交联反应构筑多孔支化聚合物，继而将其碳化，以牺牲桥联链段而保留环糊精单元形成的碳微晶来制备新型三维多孔碳材料。通过改变交联剂分子链段的刚性、长度与支化度有效调节聚合物的孔隙率进而精确调控其裂解碳的孔结构，并以其为电极材料制备高性能超级电容器。进一步采用固体核磁共振技术研究电解质在微孔与小介孔中的静电吸附过程，阐明碳材料的孔结构与其电容性能之间的关系，为提高碳材料储能性能及推动其工程化应用提供理论依据和基础实验数据。

超级电容器是一种具有广阔前景的新型电化学能源存储设备。目前限制超级电容器大规模应用的瓶颈是其中碳基电极材料制备复杂、性能仍然偏低。开发制备工艺简单、结构可控与性能优异的碳基超电容电极材料具有重要的意义。本项目以环糊精为原料，通过两种方法制备了多孔碳材料并系统研究了其超电容储能性能与储能机理：（1）以环糊精为碳源、嵌段共聚物F127为软模板，通过水热法制备了球形颗粒，将其碳化获得了碳纳米球形颗粒，进一步在其表面原位生长引入NiMoO4纳米薄片。该复合体系充分利用了金属氧化物的赝电容，同时兼具碳材料良好的电导率与化学稳定性，用于非对称电容器时表现出优异的综合性能，以KOH溶液为电解液，其电压窗口达到1.6 V，1A/g时其电容值为120 F/g，能量密度达到34 Wh/kg，10000次循环候其容量升高了24%；（2）将环糊精分别与甲苯二异氰酸酯及六亚甲基二异氰酸酯通过缩聚反应制备了高度交联聚合物，进一步将其进行高温碳化/活化制备了一系列多孔碳，发现所用异氰酸酯的分子结构对裂解产物的孔结构及电容性能有显著的影响：交联剂中芳香环比例越高，所得碳材料中微孔比例越高，因此通过前驱体分子结构设计初步实现了碳材料孔结构调控，所制备碳材料在水系电解质中最高电容值达到320F/g，离子液体中电容值达到168F/g。进一步采用固体核磁共振技术研究了孔结构对离子液体吸附行为的影响。发现微孔与离子的相互作用力随孔径增加而减小，且吸附阻力随离子浓度降低而降低，该趋势与电容测试结果一致。这些结果表明，采用固体核磁共振技术可有效探究碳微孔与离子的作用强度及吸附能力，为开发高容量碳基电荷吸附材料提供了理论基础。