■ Composite fibers and beads for flow batteries

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Description of the PhD project

The main goal of the project is to tailor new materials for flow battery application. Energy storage strategies are required for optimizing the use of renewable energy sources, like solar or wind energies. Indeed, natural intermittencies of such sources do not match with the consumer’s need. A strategy for storing energy relies on electrochemical systems where energy is accumulated or released via redox reactions. In order to increase their capacity, flow batteries, where electrolytes flow between large, have been developed. In that way, the charging phase can be adapted to the energy flux by varying the flow rate. However, new flowing materials are needed for increasing the overall capacity and power while minimizing the energy cost for their circulation.

An interesting strategy named semi-solid flow cell that couples the high storing capacity of Li-ion battery and flow battery technology, i.e. where energy-dense active materials are dispersed in a liquid electrolyte, has been recently proposed. Intercalation particles of lithium (LiFe(PO4)3, LiMn2O4, …) and conductive particles (carbon black, carbon nanotubes, …) are mixed together with polymer for obtaining a slurry that can flow. For being used in flow batteries, the amounts of intercalation particles and conductive ones are limited as they impact on the dispersion viscosity.
Here, we propose to investigate two processes for making materials having a high energy density while easily flowing. A first route is to revisit the previous concept by encapsulating the Li-intercalation particles and carbon-based particles in hydrogel beads. To reach high concentrations, we plan to follow a process based on emulsions. The key advantage is the possibility to use initially dilute dispersions to make emulsion drops and then to extract the solvent, here water, for increasing the concentration of particles. The use of microfluidic/millifluidic technologies will help to create calibrated beads along a continuous process. Optimized beads will be then confronted to the final application in a dedicated and home-made flow cell.
A second route is to propose a novel concept of flow cell by using composite material shaped as fibers. The idea is to slide a fiber on a working electrode from coil to coil that rotate, like a cassette tape. The fibers will have to be made of a composite structure with Li-intercalation particles embedded in a conductive matrix. The fibers will be produced by a wet spinning process. Typically a dope solution that contains binders, i.e. conductive particles or polymers, is injected in a counter solvent in which the solid materials coagulate under the form of a gel fiber.
The encapsulation approach may also open new opportunities for using other compounds which sourcing are less limited than lithium. It is expected that the encapsulation of zinc particles will limit the formation of dendrites around the zinc, which a major drawback in actual zinc-based batteries.


Soft matter, electrochemistry, microfluidics, energy storage, flow battery, composite materials, hydrogel, emulsion, rheology

Research unit

Chemistry, Biology & Innovation

Description of the research Unit/subunit

The institute for Chemistry Biology and Innovation (CBI) is a new Unité Mixte de Recherche (UMR) gathering research teams having skills in physicochemistry, analytical chemistry, organic chemistry, biochemistry, energy and microbiology. These teams gather experimentalists having a common aim for scientific creation and technological innovation at the interface between chemistry and biology.
Since its establishment in 2001 at ESPCI, the Laboratoire Colloïdes et Matériaux Divisés (LCMD) that belongs to CBI has developed a state-of-the-art expertise in the science of emulsions and colloids. Over the past fifteen years, the LCMD has developed tools for microfluidic drop analysis of populations of microorganisms to explore issues related to biodiversity in biology and chemistry, but also to explore emulsion science from their fabrication to their properties. It revisits and upgrades old processes of material manufacturing and is fascinated as much by the research and development that emanate from its spin off.
The candidate will benefit from the expertise in energy and soft matter from the newly established Laboratory of Matériaux Innovants pour l’Energie (MIE) that belongs to CBI.

Name of the supervisor
Nicolas Bremond

Name of the co supervisor
Annie Colin

3i Aspects of the proposal

With this PhD project, we have the ambition to perform proofs of concept of new storage devices using innovative materials. It is therefore related to advanced materials technologies belonging to the identified Key Enabling Technologies. The applications concern the improvement of energy resource efficiency. Considering their novelty, the concepts are still at an early stage of research. Nevertheless, we believe that they are sufficiently promising to already be the topic of results that may qualify for IP protection. We will therefore pay a particular attention to this point and consider possibilities of technology transfer throughout the progress of the project.
The PhD project development will cover various scientific areas like colloidal science, electrochemistry, condensed matter physics and microfluidics. The candidate will explore the electrochemical properties of original structures, from the microscopic scale (the intercalation particles) to the macroscopic one (the composite material) and gain therefore new knowledge in the field of materials science. The project will allow us to deliver new fundamental knowledge in the field of soft condensed matter with the determination of formulation and process conditions to form electronically conductive and aqueous based soft material.
There is an opportunity for the PhD student to spend a few months in the group of Gareth McKinley, the Non-Newtonian Fluid Dynamics Group at the Massachusetts Institute of Technology (https://nnf.mit.edu/) where Thibaut Divoux, a CNRS researcher at Centre de Recherche Paul Pascal, is currently a visiting researcher. They developed a device that can access to rheological and electrical properties of colloidal dispersions, a device that could used with the hydrogel beads synthetized during this project.

Expected Profile of the candidate

We look for a candidate having a background in physicochemistry or physics with knowledge in colloidal science. Knowledge and skills in electrochemistry, rheology and microfluidics is welcome.
High motivation, flexibility, autonomy, the ability to work in a highly multidisciplinary team and good interpersonal and communication skills are essential.

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