Technological research direction Development of key enabling technologies
Transfer of knowledge to industry

PhD : selection by topics

Sciences pour l'ingénieur >> Chimie physique et électrochimie
5 proposition(s).

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

Département de l'Electricité et de l'Hydrogène pour les Transports (LITEN)

01-10-2015

SL-DRT-15-0276

thibaut.gutel@cea.fr

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.

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

Département Thermique Biomasse et Hydrogène (LITEN)

Laboratoire des Technologies de l'Hydrogène

01-10-2014

SL-DRT-15-0364

guilhem.roux@cea.fr

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.

Contribution of statistical tools and the methodology of design of experiments to the development of high energy density Li-ion batteries

Département de l'Electricité et de l'Hydrogène pour les Transports (LITEN)

01-10-2015

SL-DRT-15-0485

david.peralta@cea.fr

The work will consist in evaluating the contribution of statistical tools and applying the design of experiment methodology (DOE) to optimize the working behavior of Lithium-Ion positive electrode materials. First, the work will be focused on NMC compounds and then will be enlarged to lithium rich layered oxides materials that have the potential to significantly increase the energy density of Li-Ion batteries. In both cases, the compounds will be synthesized by spray-pyrolysis route. The methodology of design of experiments will be used to optimize this synthesis and coupled with fine characterization to understand the link between synthesis parameters and the studied responses. With a DOE tool such as Minitab, the designs will be defined and will allow optimizing either their composition or their synthesis conditions or their electrochemical formation. Characterization techniques such as SEM, XRD, TGA, BET and electrochemical evaluation in coin cells will be performed for better understanding.

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

Département de l'Electricité et de l'Hydrogène pour les Transports (LITEN)

01-10-2015

SL-DRT-15-0493

celine.barchasz@cea.fr

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.

Metallic Lithium protection against alcaline electrolytes for very high energy density technologies

Département de l'Electricité et de l'Hydrogène pour les Transports (LITEN)

01-09-2015

SL-DRT-15-0531

lionel.picard@cea.fr

For automotive applications and more generally for mobility considerations, an increase in the energy density of the battery is mandatory to reach riding distance compatible with a general public use. With this objective, CEA-Grenoble developed since few years, electrochemical system of novel generation using metallic lithium coupled with Sulfur, Oxygen and soon with Nickel. These new systems will be able to reach very high energy density as high as respectively, 500Wh/kg, 1000Wh/kg and 900 Wh/kg. These technologies could be based on an alkaline electrolyte et therefore they required the development of an efficient protection on the Li-metal against water. To answer to this level of requirement, the PhD study will be based on two solutions probably complementary: a) the development of new ionically conductive solid polymer electrolytes AND b) the gelification of a electrolyte not immiscible to water. A multilayer approach could be developed starting from the studied elementary building blocks. Several experimental techniques, at the same time for the control of the synthesis (FTIR, NMR ?), for the electrochemical studies (EIS, cycling ?), for implementation (coating, spray, extrusion ?) will be implemented to bring the required level of comprehension of the charge-discharge mechanisms of the Li-metal electrode. At the end, we should be able to propose a functional prototype of Li-ion batteries with a very high energy density.

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