Hybrid electrolyte of ionic liquid and functionalized nanofiller for energy storage: dynamic and thermodynamic properties under extreme temperature and pressure conditions.

Hybrid electrolytes combining ionic liquids with nanoscale fillers offer a transformative route toward safe, high-performance energy storage; however, the lack of understanding of their charge transport over a broad range of temperature and pressure conditions limits their application. Herein, we address this issue by examining the structural, conducting, viscoelastic and thermodynamic properties of a model quasi-solid electrolyte composed of an ammonium ionic liquid and charged polyhedral oligomeric silsesquioxane (POSS) nanoparticles over an extended temperature (173-393 K) and pressure (0.1-600 MPa) range. We demonstrate that the rigid POSS scaffold creates excess free volume, reduces compressibility and thermal expansion, and introduces reversible shear-thinning viscoelasticity while maintaining efficient ion conduction. Furthermore, our high-pressure experiments reveal that ion dynamics is mostly thermally activated in this nano-hybrid electrolyte and satisfies the density-scaling concept, enabling accurate prediction of ionic conductivity over 12 decades across a wide T-P landscape. This work establishes a fundamental and predictive framework for designing next-generation nano-hybrid electrolytes for operation in extreme environments.