Decomposition temperatures and vapour pressures of selected ionic liquids for electrochemical applications
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Decomposition temperatures and vapour pressures of selected ionic liquids for electrochemical applications A. Cimini1 · O. Palumbo1 · E. Simonetti2 · M. De Francesco2 · G. B. Appetecchi2 · S. Fantini3 · R. Lin3 · A. Falgayrat3 · A. Paolone1 Received: 27 March 2020 / Accepted: 3 October 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract The thermal behaviour of selected ionic liquids, potentially useful as electrolyte components in electrochemical devices, formed by ammonium or imidazolium cations combined with bis(trifluoromethanesulfonyl)imide (C2F6NO4S2, TFSI) or bis(fluorosulfonyl)imide (F2NO4S2, FSI) anions, was investigated through thermogravimetric analysis (TGA). The liquid with the FSI anion decomposes at lower temperatures than those based on TFSI. Among ionic liquids with the TFSI anion, the stability in scanning mode with different cations decreases in the order 1-ethyl-3-methylimidazolium ( C6H11N2, EMI) > N-trimethyl-N-butylammonium (C7H18N, N1114) ≈ N-trimethyl-N(2-methoxyethyl)ammonium (C6H16NO, N111(2O1)) > N,Ndiethyl-N-methyl-N(2-methoxyethyl)ammonium (C8H20NO, N122(2O1)) ≈ N-trimethyl-N-propylammonium (C6H16N, N1113). Moreover, the vapour pressure of the six ionic liquids was obtained by means of long-lasting isothermal heating at temperatures between 150 and 300 °C. The highest pressure values were obtained in the order N1114 FSI > EMI TFSI > N122(2O1) TFSI > N1114 TFSI > N111(2O1) TFSI > N1113 TFSI. Keywords Ionic liquids · Vapour pressure · Thermal analysis · Thermal decomposition · Ammonium · TFSI
Introduction Ionic liquids (ILs) are salts with melting temperatures below 100 °C. Typically they are formed by organic cations, like imidazolium, pyrrolidinium, alkyl ammonium or phosphonium, and organic/inorganic anions, like hexafluorophosphate (PF6), tetrafluoroborate (BF4), triflate (CF3SO3, TfO), Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10973-020-10334-5) contains supplementary material, which is available to authorized users. * A. Cimini [email protected] 1
Consiglio Nazionale Delle Ricerche, Istituto Dei Sistemi Complessi (CNR-ISC), Piazzale A. Moro 5, 00185 Rome, Italy
2
Agenzia Nazionale Per Le Nuove Tecnologie, L’Energia E Lo Sviluppo Economico Sostenibile (ENEA), Materials and Physicochemical Processes Technical Unit (SSPT-PROMAS-MATPRO), Via Anguillarese 301, 00123 Rome, Italy
3
Solvionic SA, Site Bioparc Sanofi, 195 route d’Espagne, BP 1169, 31036 Toulouse Cedex 1, France
dicyanamide (C2N3, DCA), tetracyanamethanide (B(CN)4), bis(trifluoromethanesulfonyl)imide (C2F6NO4S2, TFSI) or bis(fluorosulfonyl)imide (F2NO4S2, FSI). The presence of such bulky and asymmetric ions in most cases decreases the ion–ion interactions and lowers the melting point with respect to more classical salts. ILs present peculiar physical and chemical properties as high ionic conductivity, wide thermal, chemical and electrochemical stability, high thermal capacity, good solvent capacity, combined with f
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