Quantitative and qualitative analysis for a better understanding of the aging and degradation mechanisms of electrolytes used in supercapacitors

• Published in: Journal of materials science. Materials in electronics 2022-03, Vol.33 (7), p.4568-4578
• Main Authors: Erradi, Amine, Touhtouh, Samira, El Fallah, Jaafar, El Ballouti, Abdessamad, Hajjaji, Abdelowahed, Boughaleb, Yahia
• Format: Article
• Language: English
• Subjects: Aging; Ammonia; Characterization and Evaluation of Materials; Chemistry and Materials Science; Damage detection; Degradation; Electrolytes; Infrared analysis; Infrared spectroscopy; Materials Science; NMR spectroscopy; Optical and Electronic Materials; Qualitative analysis; Quantitative analysis; Raman spectra; Raman spectroscopy; Spectroscopic analysis; Spectrum analysis; Substitution reactions; Supercapacitors; Thermogravimetric analysis; Triethylamine
• ISSN: 0957-4522; 1573-482X
• DOI: 10.1007/s10854-021-07648-x

Organic solvent-based electrolyte solutions are the main components of supercapacitors (SCs). Degradation and aging of the electrolyte affects the density energy of the SC. Therefore, in order to obtain more detailed knowledge about the degradation processes, and to identify the degradation products, relevant analytical techniques were used in this paper. The conformational changes of the tetraethylammonium ion (Et 4 N + ) were determined by Raman spectroscopy after aging tests at 70 °C and for voltages of 2.7 and 2.8 V. The obtained results showed that the Et 4 N + exhibits rotational isomerism between an all-trans conformation (tt.tt or Greek cross) and a trans-left conformation (tg.tg or Nordic cross). Moreover, the Raman spectra of both rotamers showed that (tt.tt) is more stable than (tg.tg), as well as the effect of aging temperature can be explained by the decrease of (tt.tt). In addition, a qualitative and quantitative analysis by 1 H NMR spectroscopy reveal that more than 30% of the molar percentage corresponds to products obtained (triethylamine and methanol) by the degradation of the Et 4 N + according to a proposed nucleophilic substitution reaction. Finally, a thermogravimetric analysis coupled with ATG-IR spectroscopy performed on the electrolyte of a damaged SC allowed to identify other chemical species (NH 3 , C 2 H 2 ) as breakdown products.