Key parameters governing lithium-ion mobility in an ionic liquid tethered on metal oxide nanoparticles as solvent-free hybrid electrolytes

Here, we have synthesized and characterized a series of new hybrid materials based on ionic liquids grafted on metal oxides to assess the design of solvent-free solid-state electrolytes. The aim of this study is to determine the key parameters affecting the ionic conduction properties of the materials. Several aspects were modulated, such as the chemical composition of the metal oxide (SiO₂, ZrO₂ or Al₂O₃), anchoring bond (silane chemistry or coordinative bond) and length and nature of the spacer (propyl, undecyl, or polyethylene glycol). The ionic conductivity of the hybrid composite mixed with the lithium salt reaches 4 × 10^-5 S cm^-1 without the addition of any solvents or plasticizers. This study reveals that although lithium mobility is affected by the molecular structure of the ionic liquid and grafting function, it is more driven by the organization of the ILs on the surface of the nanomaterial.