1,1-Dimethylpyrrolidinium tetrafluoroborate as novel salt for high-voltage electric double-layer capacitors

• Published in: Electrochimica acta Vol. 299; pp. 98 - 106
• Main Authors: Nguyen, Hoai Van T., Kwak, Kyungwon, Lee, Kyung-Koo
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 10-03-2019; Elsevier BV
• Subjects: 1,1-Dimethylpyrrolidinium tetrafluoroborate; Acetonitrile; Capacitance; Capacitors; Cycling stability; Electric potential; Electrochemical analysis; Electrolyte salt; Electrolytes; Gravimetry; High voltages; Ion currents; Organic chemistry; Physical properties; Propylene; Quaternary ammonium salts; Specific capacitance; Supercapacitor; Thermal stability; Voltammetry; Supercapacitor; Specific capacitance; Electrolyte salt; Cycling stability; 1,1-Dimethylpyrrolidinium tetrafluoroborate
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2018.12.155

A novel quaternary ammonium salt—1,1-dimethylpyrrolidinium tetrafluoroborate (DMPBF4), tetraethylammonium tetrafluoroborate (TEABF4), and spiro-(1,1′)-bipyrrolidinium tetrafluoroborate (SBPBF4) were prepared and dissolved in acetonitrile (ACN) and propylene carbonate (PC) for electrolyte systems of electric double-layer capacitors (EDLC). Physical properties such as thermal stability, solubility, and ionic conductivity were determined and six different electrolyte systems with 1 M concentration were electrochemically evaluated by linear sweep voltammetry, cyclic voltammetry, galvanostatic charge-discharge, and float test. To investigate the origin of the physical and electrochemical properties at the molecular level, quantum calculations for the chemical species in the electrolytes were also carried out. Compared to the standard electrolytes TEABF4 and SBPBF4, the novel DMPBF4 electrolyte exhibits a higher gravimetric capacitance, superior rate capability, and improved cycling stability. The energy and power density of EDLCs using DMPBF4 in the ACN electrolyte reach 40.61 Wh kg−1 and 8.09 kW kg−1, respectively, at the working voltage of 3.0 V. Moreover, EDLCs with DMPBF4 in ACN (PC) retain 87.9% (87.5%) of their initial capacitance after 1000 h of float testing at 3.0 V. The results indicate that DMPBF4 can be a promising electrolyte salt for EDLC application.
•TEABF4, SBPBF4 and DMPBF4 in ACN and PC were prepared as electrolytes and compared.•DMPBF4 electrolyte exhibited the highest, rate performance and cycling stability.•The improved performances of DMPBF4 is ascribed to the molecular structure.