AUTHOR=Sourjah Azra , Kang Colin S. M. , Ferrero Vallana Federico M. , Hutt Oliver E. , O’Dell Luke A. , Pringle Jennifer M. TITLE=Investigation of the benefits of the oxazolidinium cation for plastic crystal and ionic liquid electrolytes JOURNAL=Frontiers in Batteries and Electrochemistry VOLUME=Volume 3 - 2024 YEAR=2024 URL=https://www.frontiersin.org/journals/batteries-and-electrochemistry/articles/10.3389/fbael.2024.1330604 DOI=10.3389/fbael.2024.1330604 ISSN=2813-4974 ABSTRACT=

Organic ionic plastic crystals (OIPCs) are promising for developing safer energy storage electrolytes. However, there remains a significant knowledge gap regarding how different cation-anion combinations influence their core properties, and cyclic ether-based cations have received limited attention. This study reports the synthesis and characterization of OIPCs based on the N-ethyl-N-methyl-oxazolidinium cation [C2moxa]+ and demonstrates the first instance of oxazolidinium OIPCs being combined with lithium salts to create electrolytes. The [C2moxa]+ cation was paired with [FSI]-, [TFSI]-, [BF4]-, [PF6]- and [FTFSI]- anions. A study of the thermal, transport and electrochemical properties was performed. Among the new salts developed, [C2moxa][BF4] exhibited the most promising characteristics, including the lowest entropy of melting (ΔS = 7 J mol−1 K−1), an extended phase I range (10°C–130°C), the highest conductivity of 8 x 10−6 S cm−1 at 30°C, and an electrochemical stability window of 4.8 V. When the [C2moxa][BF4] and [C2moxa][FSI] were mixed with lithium salts (10, 20 and 50 mol% Li+) of the same anion, the highest conductivity of 2 x 10−3 S cm−1 at 30°C was found for the 20 mol% LiFSI/[C2moxa][FSI] electrolyte. Finally, preliminary lithium plating/stripping experiments and coulombic efficiency (CE) measurements demonstrate stability for lithium cycling for all four [C2moxa]+ electrolytes.