| dc.description.abstract | In this study, we use PC as the main solvent in our organic electrolyte which is used for carbon EDLCs, and develop the high-withstand voltage electrolyte in three stages: (1) Compare the effects of different types of sulfone additives on withstand voltage including A, B, and C. All additives will be added at 5 vol% in PC with 1.0 M TEABF4, to discuss high rate performances and the withstand voltage. (2) Select the best additive compared in the first stage and add the additive into the electrolyte at y%, x%, z% three different volume percentages. Compare high rate performances and the withstand voltage between different volume percentages of additives and before adding, which is 1.0 M TEABF4/PC. (3) According to the results of the first two stages of experiments, the optimal organic solvent was modificated. Next, compare the effects of different types of solute including TEABF4 and SBPBF4 to figure out the correlation with high rate performances and the withstand voltage. In this part, all the data indicates that SBPBF4 is superior to TEABF4 in all electrochemical performances. Next step, use SBPBF4 to prepare 1.0 M and 1.5 M two different solute molar concentration, investigating the association between the solute concentration and withstand voltage. After the final modification of the electrolyte, compare the best of the high withstand voltage electrolyte with the high-voltage commercial electrolyte, 1.5 M SBPBF4/SL+EMS.
In this study, we finally synthesized 1.5 M SBPBF4/PC+x% B, which is the most excellent high withstand voltage electrolyte. It can be observed high conductivity (15.2 mS/cm) and low resistance (Rs: 1.6 ohm; Rct: 2.3 ohm) by material analysis, result in good capacitance performance. It shows a capacitance of 113 F/g at 1 A/g and 83 F/g at 20 A/g for 3.0 V, demonstrating the excellent capacitance retention. For the withstand voltage, the potential window is up to 3.3 V and the coulombic efficiency is up to 97.5% at 3.3 V. In the last chapter of this study, we compare the material analysis and electrochemical performances after aging tests of carbon EDLCs, assembled with our best high withstand voltage electrolyte and other commercial electrolytes, to understand the key improving high withstand voltage for EDLCs in organic systems.
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