Title : Thermotropic ionic liquid crystals self assembled single ion conductors for lithium batteries
Abstract:
Lithium-ion batteries have been widely used in electronic devices due to their high energy density, long cycling stability, and long lifespan compared to other battery technologies. However, their large-scale implementation in electric vehicles and energy systems of power stations is restricted mainly due to safety concerns.
One of the most promising strategies to overcome these issues is the replacement of liquid electrolytes by solid-state materials. State-of-the art solid electrolytes are based on PEO and derivatives but their practical use is still hindered by low chemical stability and low ionic conductivity at operational temperature . Nanostructured materials such as Thermotropic Ionic Liquid Crystals (TILCs) comprising a moving cation (Li+), are currently attracting a growing interest, for several reasons: tunable self-assembly, high ionic conductivities (~10-3 S.cm-1) and single-ion conduction (Transference number t+» 1). We are investigating the properties of TILCs made of a versatile family of TILC building blocks designed to encode advantageous properties.
In this presentation, we will present our most recent results on the structural and functional properties of this new class of lithium-ion electrolytes. The various self-organized structures were established in function of molecular architecture by combining electrochemical, optical and scattering techniques. Liquid-crystals properties were established by combining results from POM (Polarized optical microscopy), DSC (Differential scanning calorimetry) and SAXS (Small angle X-Ray scattering) characterizations techniques. The structure-transport interplay was further investigated by performing advanced characterization at large-scale facilities including Quasi-Elastic Neutron Scattering and SAXS experiments, used to probe lithium-ion dynamics at molecular scale and nanoscale organization, respectively. Electrochemical characterizations such as EIS (Electrochemical Impedance Spectroscopy) was used to highlight nanostructure – ionic transport correlations (Figure 1). The potentialities of this class of materials as single-ion conductors and further routes for improvement will be discussed.
Audience take away:
- A new class of solid-state electrolyte will be presented. That will allow to widen the possibilities of solid-state electrolyte used in the next battery generations (4A-4B) for the scientific community.
- Unusual techniques and/or combinations of techniques will be presented as well as the results extracted from them. In this case, quasi-elastic neutron scattering is a very powerful techniques but not used as much as it should to describe molecular dynamics in materials. It could be applied and used in many other research fields.
- The use of TILCs can in fine facilitate the process to make lithium batteries due to their mechanical properties. It also improves the safety of the final cell by having a shut-down effect in case of thermal runaway: if the temperature inside the cells increases above the mesophase transition, the ionic conductivity is reduced thus decreasing the thermal runaway.
