Tetraethylphosphonium tetrafluoroborate electrolyte for paving the way to construct high-power and high-voltage supercapacitors

• Published in: Journal of energy storage 2024-08, Vol.96, p.112640, Article 112640
• Main Authors: Nguyen, Hoai Van T., Lee, Kyung-Koo
• Format: Article
• Language: English
• Subjects: Electrolyte salt; High power density; High voltage; Supercapacitors; Tetraethylphosphonium tetrafluoroborate
• ISSN: 2352-152X
• DOI: 10.1016/j.est.2024.112640

Phosphonium-containing electrolytes offer a new avenue for advancing high-performance supercapacitors. In this study, for the first time, we investigated the physical and electrochemical characteristics of a new phosphonium salt—tetraethylphosphonium tetrafluoroborate (TEPBF4) in various solvents including acetonitrile (AN), propionitrile (PN), propylene carbonate (PC), and trimethyl phosphate (TMP). Our investigations revealed that TEPBF4/AN electrolytes demonstrated high solubility (2.15 M), high ionic conductivity (52.2 mS cm−1), and wide electrochemical stability windows (≥4.7 V), suggesting that TEPBF4/AN emerges as a compelling alternative to conventional ammonium salts in AN for developing high-power and high-voltage supercapacitors. Our results also showed that supercapacitors based on 1 M TEPBF4/AN achieved the highest capacitance (24.7 F g−1), superior rate performance, highest energy (24.9 Wh kg−1) and power densities (6752 W kg−1) among the investigated electrolytes. Furthermore, it retained 75 % of its capacitance after 1000 h float test at a high working voltage of 3.2 V, which significantly outperformed other supercapacitors using conventional ammonium salts in AN. [Display omitted] •TEPBF4 salt in various solvents is systematically evaluated.•Phosphonium salt may set new benchmarks for high-performance supercapacitors.•The TEPBF4/AN electrolyte offers the best balanced performance.