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Thermodynamic Effect of Anion Activity on Electrochemical Reactions Involving Li + Ions in Room‐Temperature Ionic Liquids
Author(s) -
Tatara Ryoichi,
Ueno Kazuhide,
Dokko Kaoru,
Watanabe Masayoshi
Publication year - 2019
Publication title -
chemelectrochem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.182
H-Index - 59
ISSN - 2196-0216
DOI - 10.1002/celc.201900973
Subject(s) - ionic liquid , intercalation (chemistry) , inorganic chemistry , electrochemistry , chemistry , electrolyte , graphite , electrode , ion , onium , metal , raman spectroscopy , ionic bonding , electrode potential , metal ions in aqueous solution , organic chemistry , catalysis , physics , optics
The effect of Li + concentration on the electrochemical reactions of Li metal and graphite electrodes was studied in aprotic ionic liquid (P13TFSA: N ‐methyl‐ N ‐propylpyrrolidinium bis(trifluoromethanesulfonyl)amide)‐LiTFSA mixtures. The electrode potential of the Li metal was governed not only by the activity of the complex Li + ions ([Li(TFSA) 2 ] − ), but also by the free‐TFSA − anions, because the desolvation step of the complex Li + ions needed to be considered. With increasing LiTFSA concentration, the electrode potential of the Li metal increased due to increasing [Li(TFSA) 2 ] − activity and decreasing free‐TFSA − activity in the electrolyte solutions, which was supported by Raman spectroscopy results. The Li + intercalation reaction into the graphite electrode was also investigated. With increasing LiTFSA concentration, the onium cation (P13 + ) intercalation, which is a well‐known side reaction without a desolvation step, was suppressed and reversible Li + intercalation into the graphite electrode was observed.