【作者】 王艳素；

【导师】 王成扬；

【作者基本信息】 天津大学 ， 化学工艺， 2008， 博士

【摘要】 电化学电容器可能成为继锂离子电池之后的又一新型储能元件,在国民经济领域极具发展前景。一般的多孔炭材料虽具有较高比表面积和较高的理论比容量,但由于孔径较小,限制了电解质离子在其孔隙内的自由扩散运动,随工作功率增大,比容量衰减很快,电容器的比能量--比功率性能差。高功率应用(如电动汽车)的双电层电容器对炭材料的孔结构有更高的要求,以保证电容器的比能量--比功率性能,本文基于上述思想,通过制备不同孔结构的活性炭作为电容器电极材料,测试其电化学性能,旨在考察活性炭材料的孔结构与电解质离子的匹配性,以期获得制备高功率特性电容器电极材料的新方法。首先以高比表面积专业商品活性炭为电极材料,在四种有机电解液中考察电容器的电化学性能,通过恒流充放电、循环伏安和交流阻抗测试综合分析,证明在本实验条件下,电容器的比能量--比功率性能最佳,并且在实用化应用方面理想的电解质溶液为1M LiClO4/PC。然后以制备的不同孔结构的石油焦基活性炭为电极材料,以1M Et4NBF4/PC为电解液,通过具体分析电极材料的孔结构特征以及测试电化学性能,联合交流阻抗测试中的响应时间,定性地确定1M Et4NBF4/PC电解质离子所需的合适的孔结构特征为1-3nm。继而以低软化点各向同性沥青为炭材料前驱体,以乙酸镁和柠檬酸镁热解得到的电化学性能稳定的MgO为模板,通过一步炭化法成功制备出两系列高收率、高比表面积、高中孔率和可控孔结构的炭材料,其区别在于炭材料的平均孔径不同。通过考察在30wt%KOH为电解液时的电化学性能,发现两系列炭材料均具有理想的比电容量,即在25A/g的电流密度下仍能得到220F/g的比电容量;较好的功率特性,即在25A/g时容量保持率仍能达到90%以上,以及理想的保压性能,即漏电流均低于0.05mA,静置24h后仍能保持0.5V以上的电压。相比较而言,以乙酸镁为模板剂前驱体制备的炭材料体系孔径稍大,具有更理想的倍率特性和功率特性,但如果追求小电流密度放电时的高比电容量,以柠檬酸镁为模板剂前驱体制备的炭材料体系是理想的电极材料。更多还原

【Abstract】 Electrochemical double layer capacitors (EDLCs) are promising another new energy storage instrument after the lithium batteries, they will play an important role in national economy. The general carbon materials although have high surface area, the smaller pore size limits the diffusion of the electrolyte ions in the pores of the carbon. Though there is high theoretic specific capacitance, it will decrease when the working current increase, the power-energy performance gets worse. EDLCs need appropriate pore structure of the electrode materials to get higher power performance. Thus, tailoring the porous structures of carbon materials is a major goal of EDLC optimization. Based on the above depiction, in this paper, carbon materials with different pore structures were prepared, and their electrochemical performance were tested in different electrolyte in order to examine the suited electrolyte ion size and the pore structure, and expect to get new method for the electrode materials of EDLCs with higher power characteristic.First, one bought activated carbon with high surface area was used as the electrode material for the EDLCs, and tested its electrochemical performance in four electrolytes, in order to ascertain the optimal electrolyte with the best power-energy performance at fixed conditions. Results indicated that the best electrolyte was 1M LiClO4/PC in practical at the tested conditions.Then, activated carbons with different pore structures base on petroleum coke were prepared, and they were used as electrode materials of EDLCs. Their electrochemical performances were tested in 1M Et4NBF4/PC. By analyzing the pore characteristic of the electrode materials, testing their electrochemical performance and associating with the response time in the impedance spectrum, it could be confirmed qualitatively that the suited pore size range for the electrolyte ion was 1-3nm.And then, templated mesoporous carbons with high yield, high surface area, more mesopore and controllable pore structure were successfully prepared from thermoplastic precursor pitch, by the carbonization of a mixture with the MgO precursors (magnesium acetate and citrate), the difference of the prepared carbons is their different average pore size. After testing their electrochemical performance in 30wt%KOH, results indicated that the resultant mesoporous carbons could achieve perfect specific capacitance 220F/g at the current density 25A/g, and they could get good power characteristic and voltage maintenance. The capacitance maintainance of the prepared carbons could reach 90% at 25A/g, and the leakage current was lower than 0.05mA. The mesoporous carbons prepared from the mixture of magnesium acetate and the pitch got comparatively bigger pore size and obtained better power characteristic. But the mesoporous carbons prepared from the mixture of magnesium citrate and the pitch were ideal electrode materials if paying attention to the higher specific capacitance at lower current density.更多还原