Abstract
This study reports a systematic investigation of electrolytes based on new salts consisting of various cations and the bis(oxalate)borate (BOB) anion for use in electrical double layer capacitors. The quaternary ammonium salts—tetraethylammonium tetrafluoroborate (TEABF4), spiro-(1,1ʹ)-bipyrrolidinium tetrafluoroborate (SBPBF4), 1,1-dimethylpyrrolidinium tetrafluoroborate (DMPBF4), tetraethylammonium bis(oxalato)borate (TEABOB), spiro-(1,1ʹ)-bipyrrolidinium bis(oxalato)borate (SBPBOB), and 1,1-dimethylpyrrolidinium bis(oxalato)borate (DMPBOB)—were successfully prepared in high purity and dissolved in acetonitrile (ACN) at a concentration of 1.0 M. The successful synthesis of the salts was confirmed by nuclear magnetic resonance, ultraviolet–visible, and Fourier-transform infrared spectroscopies. The physicochemical properties and electrochemical performance of the prepared electrolytes, namely, thermal stability, ionic conductivity, viscosity, electrochemical stability window, specific capacitance, and durability, were investigated. Compared to the BF4-containing electrolytes, the new electrolytes based on the BOB anion, particularly the DMPBOB salt, showed dramatically enhanced high-voltage performance at elevated temperature. Electrical double layer capacitors based on 1 M DMPBOB in ACN exhibited a capacitance retention of 55.9% and a coulombic efficiency of >99% after 2000 cycles at a working voltage of 4.0 V and 45 °C. Moreover, X-ray photoelectron spectroscopy suggested that a highly stable protective layer induced by the BOB-containing electrolyte was formed on the negative electrode of the capacitor, inhibiting acute electrolyte decomposition during the cycling test.
Original language | English |
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Article number | 134649 |
Journal | Electrochimica Acta |
Volume | 321 |
DOIs | |
Publication status | Published - 2019 Oct 20 |
Bibliographical note
Funding Information:This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology ( NRF-2017R1C1B2004307 ) and the mid- and long-term nuclear research and development program through the National Research Foundation of Korea ( NRF-2017M2A8A5014710 ) funded by the Korean Ministry of Science and ICT .
Publisher Copyright:
© 2019
Keywords
- 1,1-Dimethylpyrrolidinium bis(oxalato)borate
- Conductive salts
- Electric double-layer capacitor
- High working voltage
ASJC Scopus subject areas
- General Chemical Engineering
- Electrochemistry