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Sciences pour l'ingénieur >> Chimie physique et électrochimie
4 propositions.

Synthesis of new electro-active polymers and use as electrode materials for lilthium battery

Actual lithium batteries use transition metal (Fe, Mn, Co, Ni) based compounds as electrode materials. Although their performances are satisfying, they present several important drawbacks. First these materials are expensive because they are prepared using energy-consuming techniques from expensive and rare mineral precursors. Moreover they have an important environmental footprint as some metals (Co, Ni) are toxic and hard to recycle at the end of life. Recently some new compounds which are able to reversibly form complexes with lithium have been identified: stable organic radicals in particular nitroxide radicals (TEMPO). These molecules have also the advantage to present very fast electrochemical reaction kinetics which enables to use them for high power application. The main problem of this kind of molecules is related to their important solubility in organic solvents used in electrolytes which leads to rapid drop of batteries performances along cycles of charge/discharge. To solve this issue, we propose to graft these molecules on a polymer backbone in order to limit their dissolution into electrolytes. The main interest of these organic radical functionalized polymers is that they can be easily prepared using simple organic synthesis techniques form cheap precursors. Moreover they could be easily implemented into electrodes as they can themselves act as binder mandatory to obtain electrodes with good mechanical properties.

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Département : Département de l'Electricité et de l'Hydrogène pour les Transports (LITEN) Laboratory : Start Date : 01-10-2015 ECA Code : SL-DRT-15-0276 Contact : thibaut.gutel@cea.fr

Synthesis and characterization of news cathodic materials for li-ion applications

LITEN is one of the highest European research centers in the field of the new energy technologies. LITEN research activities focus on the renewable energy, on the energy efficiency and on the high performance materials for energy. Since the early of the 90's, Li-ion technology has considerably evolved in order to outperform other storage technologies (Pb, Ni-Cd, Ni-MH,?). With the rapid development of hybrid and electric vehicles, it is necessary to find new solutions to increase the battery life. So, it is now important to develop new generations of cathodic materials in order to pass the threshold of 250 Wh/kg and to reach in the second step 350 wh/kg. Literature reports that some rock-salt materials are able to reach these specifications. The selected student will be assigned of the mission of synthesis, characterization and evaluation of new materials of this family.

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Département : Département de l'Electricité et de l'Hydrogène pour les Transports (LITEN) Laboratory : Start Date : 01-10-2015 ECA Code : SL-DRT-15-0339 Contact : david.peralta@cea.fr

Electrodes microstructural optimisation of Solid Oxide Cells for co-electrolysis operation

Because of its great potential, hydrogen production by high temperature steam electrolysis has received an increasing national and international interest in recent years. The hydrogen produced by water electrolysis if taking advantage of sustainable energy sources would constitute an energy carrier with low carbon footprint and would allow limit greenhouse gas emission. In this frame, co-electrolysis at high temperatures of steam and carbon dioxide constitutes a promising process. Indeed, it allows valorising CO2 by producing a syngas of H2 and CO. This mixture can be further transformed by chemical processes into methane or liquid fuel for both stationary and transport applications. However, the electro active components of electrolyser, i.e. the solid oxide cells, have been optimised for the classical operation under hydrogen. Electrodes microstructures as well as cell dimensions are not adapted for the specific operation in co-electrolysis. In the thesis, it is proposed to design electrodes microstructures and cell dimensional characteristics in order to improve the cell efficiency and reliability when operated in co electrolysis. The morphological optimisation will be carried out thanks to a ?multi physic? and ?multi scale? model, already available at CEA.

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Département : Département Thermique Biomasse et Hydrogène (LITEN) Laboratory : Laboratoire des Technologies de l'Hydrogène Start Date : 01-10-2014 ECA Code : SL-DRT-15-0364 Contact : guilhem.roux@cea.fr

Investigation of lithium/sulfur battery by means of in situ and operando X-ray tomography

This thesis will aim at studying and improving the understanding of the lithium/sulfur (Li/S) battery technology, its discharge and failure mechanisms, by means of various tomographic measurements. Indeed, this battery technology is quite promising in terms of energy density, costs and sulfur material abundance. However, the discharge mechanism and reasons for failures of this system are still unclear, and deserve further investigation. To this purpose, the sulfur electrode as well as full Li/S cells will be characterized thanks to in situ and operando tomographic measurements. This thesis will be held between two laboratories: CEA-LITEN and ESRF. The preparation of the cell components and the assembly of Li/S cells will be done in CEA-LITEN, as well as the electrochemical characterizations of the batteries, while the tomographic measurements will be performed in ESRF. The thesis will finally aim at better understanding the failure mechanisms of Li/S cells and sulfur electrodes during cycling, in order to propose innovative materials that could improve the electrochemical response of the system, in terms of discharge capacity and capacity retention.

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Département : Département de l'Electricité et de l'Hydrogène pour les Transports (LITEN) Laboratory : Start Date : 01-10-2015 ECA Code : SL-DRT-15-0493 Contact : celine.barchasz@cea.fr
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