Crystal structure and cation-anion interactions of potassium (Difluoromethanesulfonyl) (trifluorome thanesulfonyl)imide

Eduardo Sánchez-Diez; Lorena Garcia; Oier Arcelus; Lixin Qiao; Leire San Felices; Javier Carrasco; Michel Armand; Maria Martínez-Ibañez; Heng Zhang

doi:10.3389/fchem.2023.1191394

Crystal structure and cation-anion interactions of potassium (Difluoromethanesulfonyl) (trifluorome thanesulfonyl)imide

Front Chem. 2023 Jul 12:11:1191394. doi: 10.3389/fchem.2023.1191394. eCollection 2023.

Authors

Eduardo Sánchez-Diez¹, Lorena Garcia¹, Oier Arcelus¹, Lixin Qiao¹, Leire San Felices², Javier Carrasco^{1

3}, Michel Armand¹, Maria Martínez-Ibañez¹, Heng Zhang⁴

Affiliations

¹ Centre for Cooperative Research on Alternative Energies (CIC EnergiGUNE), Basque Research and Technology Alliance (BRTA), Vitoria-Gasteiz, Spain.
² Servicios Generales de Investigación SGIker, Facultad de Ciencia y Tecnología, Universidad del País Vasco, UPV/EHU, Bilbao, Spain.
³ IKERBASQUE, Basque Foundation for Science, Bilbao, Spain.
⁴ Key Laboratory of Material Chemistry for Energy Conversion and Storage (Ministry of Education), School of Chemistry and Chemical Engineering Huazhong, University of Science and Technology, Wuhan, China.

Abstract

Sulfonimide salts are of great interest for battery use thanks to their special properties including sufficient superior chemical/thermal stabilities, structural flexibility, etc. In particular, the hydrogen-containing sulfonimide (difluoromethanesulfonyl)(trifluoromethanesulfonyl)imide anion {[N(SO₂CF₂H) (SO₂CF₃)]^-, DFTFSI^-}, stands out owing to its suppressed anion mobility and superior electrochemical properties. We herein report the structural analyses of potassium (difluoromethanesulfonyl)(trifluoromethanesulfonyl)imide {K [N(SO₂CF₂H) (SO₂CF₃)], KDFTFSI} by virtue of single crystal X-ray diffraction and computational approaches. Our results reveal that KDFTFSI crystallizes in a orthorhombic cell (space group: Pbcn) comprising of cationic and anionic layers, which is similar to the conventional sulfonimide salt, potassium bis(trifluoromethanesulfonyl)imide {K [N(SO₂CF₃)₂], KTFSI}. Gas-phase density functional theory calculations show that the conversion from trans to cis DFTFSI^- anions is hindered due to the presence of stabilizing intramolecular H-bonding interactions in the trans conformer; yet interaction with K⁺ substantially minimizes the energy difference between the two conformers due to the formation of strong tridentate K⁺ coordination with oxygen atoms in the cis KDFTFSI. This work is anticipated to provide further understanding on the structure-property relations of hydrogenated sulfonimide anions, and thus inspire the structural design of new anions for battery research.

Keywords: (Difluoromethanesulfonyl)(trifluoromethyanesulfonyl)imide; Cation-anion interaction; Crystal structure; Dihedral angle; Hydrogen-containing sulfonimide anion.