Tuning Ionic Liquids with Charged Polyhedral Oligomeric Silsesquioxane Nanoparticles for Highly Conductive Quasi-Solid Electrolytes

Electrolytes are fundamental materials that have been used in various electrochemical devices, including fuel cells and batteries. Herein, we report a new class of quasi-solid electrolytes based on ionic liquids (ILs) and multiply charged polyhedral oligomeric silsesquioxane (POSS) nanoparticles that overcome the traditional conductivity–mechanical stability trade-off in solid electrolytes. By precisely controlling the stoichiometric interaction between octa-charged POSS nanoparticles and selected ILs, we achieve unique combinations of properties: room-temperature ionic conductivity σ_dc^RT up to 4 mS/cm, matching or exceeding the parent ILs; reversible shear-thinning behavior enabling easy processing; and exceptional long-term stability against phase separation. Systematic characterization reveals that the 30 wt % POSS loading enhances interfacial charge transfer near the NPs or creates an optimal percolating network where cation–nanoparticle interactions favor fast anion transport. At the same time, the charged POSS framework provides mechanical stability to the quasi-solid electrolyte.