Pyrrolidinium-based gel composites for reprocessable, flame-retardant electrolytes

Abstract

Flame-retardant and reprocessable gel composites composed of a pyrrolidinium-based poly(ionic liquid) were successfully prepared by incorporating surface-modified SiO₂-nanoparticles functionalized with ionic liquids or multiple hydrogen bonding groups (ureidopyrimidinones). Covalent functionalization was verified by CP-MAS ²⁹Si NMR, FT-IR, and thermogravimetric analysis. Surface-modified NPs significantly improved the dynamic characteristics of the synthesized gel composites, yielding composites with enhanced reprocessability and remarkable mechanical flexibility, reaching an elongation at break of up to 460%, achieved solely through reversible dynamic interactions without the need for permanent covalent crosslinking. Upon reprocessing, the ionic conductivity of the gels was efficiently restored, reaching values of 2.2 × 10⁻⁴ S cm⁻¹ at room temperature. The composites further exhibited excellent thermal stability up to 330 °C and an inherently flame-retardant nature classified as UL 94 V-0 grade. These combined features underscore the potential of the developed PIL-based gel composites for safe, durable, and high-performance applications in electrochemical and flexible devices.