Lithium Based Ionogel as Solid State Electrolyte: Dynamics of Confined Ionic Liquid, a Neutron Diffusion Study

Ionic liquids (ILs) have been the focus of a rapidly growing number of studies in materials science since early 2000’s. Their liquid state is advantageous for their properties but often prevents their applications in devices which most often need solid state shaping. Thus, several approaches to get round this drawback are under investigation. Polymerizing the IL, grafting any of its ions onto a substrate, making physical gels … We have focused our work on confining IL in host matrices, resulting in solid materials, as well as leaving the dynamics features of the liquid state. The host matrix can be either fully inorganic, mixed polymeric and inorganic or fully polymeric. In each case, there is a continuous silica-to-IL interface, where silica has been obtained through sol-gel route. The solid obtained is thus endowed with properties of the choosen IL simultaneously with those of a robust host backbone including a silica interface.

The resulting ionogels, fully inorganic, mixed polymeric and inorganic or fully polymeric, are showing striking properties. The synergetic associations allow most often to lower the melting point of IL as well as to increase the ionic transport. It will be shown that the continuous interface and the confinement at nanoscale are modifying advantageously intensive properties of ILs. The conclusions are supported by results of studies with local probes (NMR, QENS, relaxometry, PGSE) and macroscopic measurements (CIS, BDS, DSC, IR) which show complementary information on chemistry, texture and physics (charge transport, dynamics, transmittance, dielectric …).

Among several potential applications, we are focusing on supercaps, lithium batteries, electrochromic and photochromic devices. The macroscopic observation of the properties of these solid devices shows either equal or superior properties as referred to genuine ILs.