双电层电容器用离子液体/碳酸酯电解液的调制与性能

(1.西安科技大学 材料科学与工程学院,陕西 西安 710054; 2.西安科技大学 安全科学与工程学院,陕西 西安 710054)

双电层电容器; 电解液; 离子液体; 碳酸酯; 电压

Properties of electrolytes consisting of ionic liquid and carbonate for electric double layer capacitor
LU Hai1,DU Hui-ling1,ZHENG Bin1,ZHENG Xue-zhao2

(1.College of Materials Science and Engineering,Xi'an University of Science and Technology,Xi'an 710054,China; 2.College of Safety Science and Engineering,Xi'an University of Science and Technology,Xi'an 710054,China)

electric double layer capacitor; electrolyte; ionic liquid; carbonate; voltage

备注

将离子液体1-乙基-3-甲基咪唑四氟硼酸盐(EMIBF4)混合碳酸丙烯酯(PC)及各种链状碳酸酯溶剂调制了一系列电解液用于双电层电容器中。文中表征了各款电解液的基本理化性质,考察了溶剂组成对电容器循环、倍率与耐压等性能的影响。研究发现,EMIBF4与碳酸酯溶剂混合能够显著降低电解液黏度、提高离子电导率。各款电解液组装的活性炭双电层电容器基本上都具有0~3 V的稳定电位窗口,而上限电压提高至3.2 V时容量会出现快速衰减。相比之下,将PC和DMC二元混合调制的离子液体电解液虽然对电容器的耐压性能略有影响,但是可以获得较之其他电解液相对更高的比电容量和更优的倍率性能,其在0~3 V电压区间、0.5 A/g和5 A/g电流密度下的比电容量分别达到114 F/g和100 F/g,经5 000次循环后的容量保持率达92%,电容器最大能量密度达35.2 Wh/kg.以上结果表明,合理调控碳酸酯溶剂的种类与配比,咪唑类离子液体/碳酸酯电解液可以实现高性能3V基双电层电容器的有效构建。

Several electrolytes of electric double layer capacitor(EDLC)were prepared by mixing ionic liquid(IL),1-ethyl-3-methylimidazolium tetrafluoroborate(EMIBF4),propylene carbonate(PC)and other carbonates with chain structure.The physical and chemical properties of the electrolytes were characterized,and the effects of solvent composition on the electrochemical performance(cycle,rate and voltage resistance)of the EDLC were investigated.It is found that the addition of carbonates into EMIBF4 can significantly reduce viscosity and improve ionic conductivity of the electrolyte.The stable potential windows of the IL-based electrolytes with various solvent compositions can reach 0~3 V when matched with active carbon electrode,while the limited upper voltage of 3.2 V results in rapid capacity decay.In comparison,the IL electrolyte with PC/DMC binary solvents helps the EDLC to achieve higher specific capacitance and better rate capability than other electrolytes,although the 3 V toleration ability is slightly lower than that with single PC.The specific capacitance reaches 114 F/g and 100 F/g at 0.5 A/g and 5 A/g,respectively,and the capacity retention after 5 000 cycles between 0 V and 3 V is 92% for the PC/DMC case.The EDLC in the PC/DMC system yields a maximum energy density of 35.2 Wh/kg.The above results suggest that the imidazolium-type IL/carbonate electrolyte can realize the construction of high-performance 3V based EDLCs as long as the types and proportion of carbonate solvents are properly regulated.