Collective Ion Dynamics in Ionic Plastic Crystals: The Origin of Conductivity Suppression

• DOI: 10.1021/acs.jpcc.3c03590
• Publication Date: 2023-08-09T11:34:52Z
• Authors: Ivan Popov; Haijin Zhu; Airat Khamzin; Curt Zanelotti; Louis Madsen; Maria Forsyth; Alexei P. Sokolov
• Keywords: Plastic crystal; Phosphonium; Fast ion conductor; Hexafluorophosphate

Organic ionic plastic crystals (OIPCs) appear as promising materials to replace traditional liquid electrolytes, especially for use in solid-state batteries. However, OIPCs show low conductive properties relative which presents an obstacle their widespread applications. Recent studies revealed very high ion mobility the solid phases of OIPCs; yet, conductivity is significantly (∼100 times) suppressed because strong ion–ion correlations. To understand origin correlations OIPCs, we employed broadband dielectric spectroscopy, light scattering, and NMR diffusion measurements diethyl(methyl)(isobutyl)phosphonium-hexafluorophosphate [P1,2,2,4][PF6]. The results confirmed significant decrease this OIPC through Surprisingly, these suppress charge displacement on rather long time scales comparable ∼1.5 nm length scale. We ascribe observed phenomena momentum conservation motion mobile anions emphasize that a microscopic understanding might enable design with strongly enhanced conductivity.