【作者】 时志强；

【导师】 王成扬；

【作者基本信息】 天津大学 ， 化学工艺， 2007， 博士

【摘要】 本论文以研制廉价、高比能量和高比功率的电化学电容器炭电极材料为目的,开展了以酚醛树脂、石油焦和三聚氰胺树脂为碳前驱体制备高性能炭电极材料的研究工作,对炭电极材料的制备工艺、结构、电容性能和储能机理进行了深入研究。本论文首次提出以热固性酚醛树脂为原料,采用CO2物理活化法制备低成本炭电极材料,系统考察了活化温度和活化时间对酚醛树脂基活性炭结构及电容性能的影响。最优实验条件下制备的酚醛树脂基微孔炭具有超过2200m2/g的比表面积、孔径集中分布在1～2nm,其在30wt% KOH水溶液中具有高达211.6F/g的放电比电容、良好的功率性能和循环性能。采用KOH化学活化制备了不同比表面积和孔径分布的酚醛树脂基多孔炭,考察了其在30wt% KOH溶液和1M Et4NBF4/PC电解液中的电容性能。研究结果表明:酚醛树脂基多孔炭在水系电解液中不存在“离子筛分”现象,大于0.4nm的孔隙均能形成有效的双电层;而其在有机电解液中出现明显的“离子筛分”现象,小于0.7nm的极微孔中不能形成有效双电层;1～2nm的微孔是形成双电层的最佳孔径范围,适量的中孔有利于提高电容器的功率性能。采用KOH活化石油焦制备纳米微晶炭,研究了原料的预炭化和活化温度对其结构和电容性能的影响,并讨论了其实用化的可能性和新型储能机理。实验发现:适当的炭化处理与活化工艺的结合能够实现对纳米微晶炭孔结构和微晶结构的调控;获得的纳米微晶炭保持低比表面积、大层间距和高电极密度,并具有优于商品活性炭YP15的电容性能。恒电流充放电和半原位XRD分析表明,“电化学活化”的实质是电解质离子嵌入有序或无序炭微晶层间的过程。首次采用高分辨投射显微镜(HRTEM)观察到纳米石墨微晶炭内部有序炭微晶层间距的增大和表面类SEI膜的形成,结合扫描电镜观察和EDS能谱分析提出纳米微晶炭的插层储能机理。首次直接炭化商业产三聚氰胺树脂制备富氮炭材料,用作电化学电容器电极材料。研究发现:小比表面积(102.6m2/g)的富氮炭,具有高达205.5F/g的质量比电容、较好的功率性能和优异的循环稳定性。比电容和XPS分析表明,良好的电容性能与富氮炭材料表面的吡咯氮或羟基吡啶氮提供的准电容作用有关。更多还原

【Abstract】 This paper was addressed on studying the carbon electrode materials for electrochemical capacitors with low cost, high specific energy and high power density. High performance carbon electrodes for capacitors were prepared using phenol-formaldehyde resin, petroleum coke and melamine resin as precursor. The preparation technology, structure, capacitance performance and the mechanism of energy storage for carbon electrode material were investigated deeply.The low cost carbon electrode was prepared by CO2 one-step activation of resole phenol-formaldehyde resin for the first time. The effect of activation temperature and activation time on the structure and capacitance performance of phenolic resin based micropore carbon was investigated systematically. The phenolic resin based micropore carbon prepared under optimum conditions had specific surface area over 2200m2/g and pore size of 1~2nm. The specific discharge capacitance was as high as 211.6F/g in the 30wt% KOH aqueous solution showing excellent power performance and cycle performance.The phenolic resin based porous carbon with different specific surface area and pore size distribution was prepared by KOH activation. The capacitance performance was investigated both in 30wt% KOH aqueous and in 1M Et4NBF4/PC electrolyte.The phenolic resin based porous carbon did not exist“ion sieving”in aqueous electrolyte since almost all the pores could form effective electric double layer, while it exhibited“ion sieving”in organic electrolyte because the pores of size smaller than 0.7nm could not form effective electric double layer. Micropore of 1~2nm was the optimum pore size for the formation of electric double layer, and suitable amount of mesopore was beneficial to the improvement of power capacitance for capacitors.The nanocrystallite carbon was prepared by KOH activation using petroleum coke as precursor. The effect of pre-carbonization temperature and activation temperature on the structure and capacitance performance of nanocrystallite carbon was investigated. The practical possibility and mechanism of novel energy storage were discussed. It was found that the combination of pre-carbonization and activation could realize the control of pore structure and nanocrystallite structure. And material with low specific surface area, large space interlayer and high electrode density could be obtained which displayed better capacitance performance than that of commercial activated carbon YP15. The essential of“electrochemical activation”was the process for the insertion of electrolyte ion into ordered or disordered crystallite interlayer which was confirmed by galvanostatic charge/discharge test and semi in-situ XRD analysis. For the first time the increase of interlayer space for ordered carbon crystallite and the formation of SEI-like layer on the surface of nanocrystallite carbon were observed by HRTEM. The mechanism of intercalation energy storage was shown by the combination of SEM, HRTEM observation and EDS spectra analysis.The nitrogen-enriched carbon material with low surface area was prepared using commercial melamine resin as precursors by carbonization for the first time. Results showed that the nitrogen-enriched carbon with low surface area had a high gravimetric capacitance of 205.5F/g, good power capacitance and cycle stability. The excellent power performance was associated with the pseudocapacitance provided by pyrrolic nitrogen or pyridine nitrogen on the surface of nitrogen-enriched carbon materials.更多还原