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.