Synthesis and ionic conductivity of organic ionic crystals consisting of quaternary phosphonium cations and cyclic perfluorosulfonylamide anion

Abstract Organic ionic species are promising candidate for innovative solid electrolyte matrices. In our previous work, we successfully synthesized quaternary ammonium salts exhibiting plastic crystalline behavior over a wide temperature range, specifically focusing on cyclic perfluorosulfonylamide (CPFSA) anion. However, reports on CPFSA-based organic ionic species remain scarce. Herein, novel phosphonium salts with CPFSA anion were synthesized to evaluate the structure–property relationship. Analogous ammonium salts were also synthesized to investigate how cation center elements affect the crystal structures, phase transitions, and ionic conductivities.