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Water in Protic Ionic Liquids: Properties and Use of a New Class of Electrolytes for Energy‐Storage Devices
Author(s) -
Stettner Timo,
Gehrke Sascha,
Ray Promit,
Kirchner Barbara,
Balducci Andrea
Publication year - 2019
Publication title -
chemsuschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.412
H-Index - 157
eISSN - 1864-564X
pISSN - 1864-5631
DOI - 10.1002/cssc.201901283
Subject(s) - ionic liquid , electrolyte , electrochemistry , capacitance , ionic conductivity , supercapacitor , conductivity , chemical engineering , inorganic chemistry , aqueous solution , capacitor , chemistry , electrochemical window , materials science , electrode , voltage , organic chemistry , catalysis , physics , engineering , quantum mechanics
In this work, the properties of “water‐in‐PIL” (PIL=protic ionic liquid) electrolytes are reported based on 1‐butylpyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr H4 TFSI). Taking advantage of experimental and theoretical investigations, it is shown that the amount of water inside the electrolyte has a dramatic effect on the viscosity, conductivity, density, cation–anion interplay, and electrochemical stability of Pyr H4 TFSI. The impact of water on the properties of this ionic liquid also affects its use as an electrolyte for electrochemical double‐layer capacitors (EDLCs). It is shown that the presence of water improves the transport properties of Pyr H4 TFSI, with a beneficial effect on the capacitance retention of the devices in which these electrolytes are used. However, at the same time, water reduces the operative voltage of EDLCs containing this PIL as the electrolyte and, furthermore, it has a strong impact on the inactive components of these systems. To suppress this latter problem, and to realize EDLCs with high stability, the use of inactive components stable in aqueous environment appears necessary.