Abstract
The energy storage device with high energy and power densities with good cyclability is required. In principle, the energy density or specific energy of supercapacitor is proportional to the square of working potential window. In this work, different ionic liquids (ILs) with wide working potential windows are used as the electrolyte of supercapacitors using activated carbon. ILs of imidazolium-based structures with different sizes of alkyl chain (i.e., ethyl, propyl, butyl and pentyl) are synthesized to investigate their effects on the performance of supercapacitors. Also, we fabricated the 18650 cylindrical cells of symmetrical supercapacitors. The device with EMI-TFSI provides the highest performance following by PMITFSI, BMI-TFSI and PTMI-TFSI, respectively. This device reveals the specific capacitance of 3.44 F/g Cell (ca. 89 F a cell) and 22.28 F/g Active Material at an applied high current of 100 mA per cell. Moreover, optimum specific energy of this device (3.30 Wh kg-1 and 21.33Wh kg-1 as function of cell mass and active mass, respectively) is higher than PMI-TFSI, BMI-TFSI and PTMI-TFSI around 15, 80 and 85 %, respectively. The results elucidate that the size of alkyl chain of imidazolium cation play the importance role in electrochemical of device. We hope that these results may pave a way to design the structure of IL electrolyte for high energy storage in large-scale production.