@@ 与传统的可充电化学电池相比, 超级电容器(Supercapacitors)具有更高的比功率和更长的循环寿命[1,2], 近年来在电动汽车和其它大功率设备应用方面得到广泛应用.对于应用非水有机电解液的超级电容器, 虽可获得更高的比能量, 但由于电解液中有机溶剂在高温下易挥发或降解, 过充时易燃易爆, 存在一定的安全隐患, 因此选用具有"零"蒸汽压、良好热稳定性、宽电化学窗口和高电导率的离子液体(Ionic liquids)替代传统有机电解液成为目前的研究热点[3～7].相关研究结果表明, 除了配制物理化学性能优良的新型离子液体体系以外, 由于离子液体中阴阳离子多具有较大的离子尺度, 因此选择适宜微结构特征的电极材料与之相匹配是实现离子液体在超级电容器中有效应用的关键所在[8～10].本文选择以二(三氟甲基磺酰)亚胺锂(LiTFSI)和2-噁唑烷酮(OZO)为基的离子液体作为电解液[11,12], 对其与不同微结构特性(孔径、比表面积等)的炭材料[碳纳米管(CNTs)、中孔活性炭(MEACs)和微孔活性炭(MIACs)]间的电化学兼容性进行了研究, 其中中孔活性炭适宜的孔径分布满足具有较大离子尺寸的离子液体电解质材料的离子正常迁移, 同时又具备较高的比表面积, 可以保证超级电容器具有较高的比电容特性.%Electrochemical double layer capacitors(EDLCs) composed of various carbon electrodes with different pore sizes and surface areas [ carbon nanotubes, mesoporous activated carbons (MEACs) and microporous activated carbons ] and ionic liquids based on lithium bis ( trifluoromethane sulfone ) imide ( LiTFSI )with 2-oxazolidinone (OZO) as the electrolyte were studied. Electrochemical performances were evaluated with quantum chemistry calculations, cyclic voltammetry and galvanostatie charge-discharge tests. The LiTFSI-OZO system exhibits superior physicochemical properties, such as a wide liquid-phase range and high ionic conductivity. The configurations of ions ( “free” ions, contact ion pairs and aggregates) in the electrolyte and their interactions have an important influence on the electrochemical performance of the LiTFSI-OZO system. The EDLCs containing MEACs, which have the largest surface area and most compatible pore size of the carbon materials, possesses the highest specific capacitance of 184.6 F/g. This work shows that it is necessary to closely match the pore sizes of electrode materials with the ion sizes of the electrolyte system to optimize the performance of novel room temperature ionic liquids.
展开▼
