LEPMI - Rubrique MIEL Materiaux Moleculaires

Inorganic- and organic-based electrolytes and electrodes for electrochemical generators

This thematic consists in designing, controlling, and optimizing the chemistry and morphology of functional polymeric materials in order to enhance their ionic or electronic transport properties and control their reactivity.

To achieve high performance materials, our research works are associated with organic synthesis to prepare functional monomers comprising ionic and/or solvating functions, or ionic liquid. These functional monomers are the elemental bricks to prepare solvating and/or single-ion-conductor (ionomers), with rigid or flexible backbone, for proton or anion exchange membrane fuel cell, lithium-polymer batteries, divalent cationic based batteries, dye-sensitive solar cell, and redox flow batteries. Our activity is focused on electrolytes based on polymer, gelled or dry, redox materials (polymers or organic molecules) with an expertise in the design and synthesis of materials, and on their physico-chemical properties.

The scientific approaches we carry out are through projects combining innovative materials and fundamental aspects to understand the relationships between structures – functionalities – physico-chemical properties - performance in the system.

One of the flagship main projects on polymer electrolyte is associated with the design of original polymers forming ion-conducting nano-structured membranes, different from current technologies. This nano-structuration permits to obtain high-performance electrolytes combining: high mechanical strength and conductivity, antagonist properties by nature in polymer materials, in a wide temperature range.

Solvating polymer and ionomers

This activity focused on the design and characterization of solvating polymer based electrolyte (polyethylene oxide or polycarbonate) aiming to lever the main technological barriers of Lithium metal polymer (LMP) batteries and to design electrolytes for divalent ion-based accumulators (Ca, Mg), and in particular to reduce the operating temperature and improve the durability by controlling the metal/electrolyte interface. Original approaches in synthesis (single-ion-conductor polymer, block copolymers) and/or elaboration (composite membrane: ionomer + nanocharge) leads to ionic conductivities higher than 10-4 S/cm at 30°C as well as enhanced durability by a synergy of properties, single-ion-conducting and high mechanical properties.

Aromatic architectured polymer electrolyte

High performance multi-block copolymers comprising ionic blocks, with perfluorosulfonic or perfluorosulfoimide functions, ensuring ionic conduction, and hydrophobic blocks ensuring mechanical properties were designed and synthesized. The incorporation of these highly dissociated ionic function and the material structuration at nanoscale permits high performance in term of conductivity and chemical, thermal, electrochemical stability. An in-depth study of the impact of the molecular architecture and shaping conditions on the morphology and functional properties of the membrane was performed. The use of these copolymers as electrolytes and as electrode binders for PEMFC systems and LMP batteries led to exceptional results in terms of electrochemical performance and durability.

Ionic polyliquids

Ion polyliquids (PILs) with polysiloxane structure were synthesized and characterized as electrolytes in dye-sensitive solar cells using bimodal architected TiO2 electrodes. The optimization of the electrode architecture and the functionalization of the PILs allowed, via the optimization of the interfaces, to obtain yields similar to liquid electrolyte based cells with a significant improvement in the durability of the devices, for several months, attributed to the presence of a polymer electrolyte instead of a liquid electrolyte.

Organic materials for batteries

This activity involves organic materials as a cathode element for battery and is based on a relevant choice of organic targets to achieve high capacities with materials whose functionalization permits to adjust the target depending on to the electrolyte. Our studies have been extended to studies of compounds with joint redox and luminescence properties. After demonstrating that under photochemical stimulus, the absorption of a photon permitted to recharge the battery at a lower potential, this activity was continued by combining a photosensitive substrate (ZnO) and a grafted redox coordination complex.