Polymer/Ionic Liquid Thermoplastic Electrolytes for Energy Storage Processed by Solvent Free Procedures

A series of poly(ethylene oxide) (PEO)/lithium trifluoromethanesulfonate (LiTf)/room temperature ionic liquid (RTIL) composite electrolytes has been prepared by melt compounding, using sepiolite modified with d-α-tocopherol polyethylene glycol 1000 succinate (TPGS-Sep) as filler. These electrolytes have been extensively characterized, including thermal stability, relaxations and transitions, rheology, conductivity, ion diffusivity, and salt dissociation. This work shows how the ability of TPGS-S to act as a physical cross-linking site for PEO allows these electrolytes to behave as solids at T > 70 °C, while the abundance of an ionic liquid phase makes the ion diffusion coefficients at 25 °C considerably high, closer to those of a viscous liquid than to those of a solid phase. This combination of rheological and electrical properties, together with their simple and scalable preparation by melt-compounding, makes them a very appealing new class of sustainable electrolytes. This same concept can be applied t...