隔膜对双电层电容器和混合型电池-超级电容器的电化学性能的影响

摘要

隔膜是双电层电容器和混合型电池-超级电容器等电化学储能器件的重要组成元件.本文采用1 mol∙L-1四乙基四氟硼酸铵的丙烯碳酸酯电解液制备了基于活性炭的扣式双电层电容器，并采用1 mol∙L-1六氟磷酸锂锂离子电解液制备了(LiNi0.5Co0.2Mn0.3O2+活性炭)/石墨体系的混合型电池-超级电容器.研究了不同类型隔膜的物理化学性能，以及其对双电层电容器和混合型电池-超级电容器的电化学性能的影响.四种隔膜分别是无纺布聚丙烯毡、多孔聚丙烯薄膜、Al2O3涂层的聚丙烯薄膜和纤维素纸隔膜.进行了表面形貌、差示扫描量热、电解液吸液量和表观接触角测试表征.电化学测试表明，采用纤维素隔膜的双电层电容器具有最高的比电容和更优的倍率性能，电容器的自放电性能差别不大.而对于混合型电池-超级电容器，采用聚丙烯薄膜和无纺布聚丙烯毡隔膜器件的比容量比其它器件约高20%，且采用纤维素隔膜的器件自放电率最高.%Separators are important components in electrochemical energy storage devices such as electrical double layer capacitors (EDLCs) and hybrid battery-supercapacitors. We prepared activated carbon-based EDLCs using an electrolyte of 1 mol∙L-1 tetraethyl ammonium tetrafluoroborate (Et4NBF4) in propylene carbonate (PC), and (LiNi0.5Co0.2Mn0.3O2+activated carbon)/graphite hybrid battery-supercapacitors using a 1 mol∙L-1 lithium hexafluorophate (LiPF6) Li-ion electrolyte. The physicochemical properties and effect of various separators on the electrochemical properties of the EDLC and hybrid battery-supercapacitor were studied. The four separators were nonwoven polypropylene (PP) mat, porous PP membrane, Al2O3-coated PP membrane, and cellulose paper. The surface morphology, differential scanning calorimetry, electrolyte uptake, and apparent contact angle were investigated. The electrochemical characterizations of coin cells indicated that the EDLC with cellulose separator had the highest specific capacitance and rate capability. Differences in the self-discharge of the four cells were not obvious. The specific capacities of the hybrid battery-supercapacitors with PP membrane and nonwoven PP mat separators were approximately 20% higher than the others. The capacitor with the cellulose paper separator had the highest self-discharge rate.