Scientific direction Development of key enabling technologies
Transfer of knowledge to industry

PhD : selection by topics

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

New thin film solid electrolytes with high ionic conductivity for lithium-ion microbatteries

Département Composants Silicium (LETI)

Laboratoire Micro-Batteries Embarquées

01-10-2017

SL-DRT-17-0013

frederic.lecras@cea.fr

The aim of the work will be the development of new glassy inorganic electrolytes able to meet both conductivity and process requirements for the realization of microbatteries with enhanced performance. These sulfide or oxide type materials, based on network formers comprising a metal or semi-metal element, will be deposited as thin films by radio-frequency magnetron sputtering of home-made targets, using an equipment connected to a glovebox. Different strategies dealing with materials composition (type of network former, synergic effect of mixed formers) and/or structure (glass-ceramics) will be carried out to get optimal performance in terms of ionic and electronic transport, chemical and electrochemical stability. Numerous techniques will be used to determine the chemical composition of the thin films (ICP, Rutheford Back-scaterring Spectroscopy, Electron Probe Micro Analysis, Auger spectroscopy, ?) and to characterize their structure (X-ray diffraction, Raman spectroscopy, XPS, TEM,?) and their morphology (MEB-FEG). Impedance spectroscopy measurements performed at different temperatures will allow determining conduction properties (ionic conductivity, activation energy). In the course of this study, the behavior of selected electrolytes will be assessed in real microbatteries. The work will be carried out in the CEA/CNRS team located at ICMCB (Bordeaux).

All-solid-state lithium(-ion) microbatteries for high temperature applications

Département Composants Silicium (LETI)

Laboratoire Micro-Batteries Embarquées

01-10-2017

SL-DRT-17-0026

frederic.lecras@cea.fr

The aim of this thesis is the development of all-solid-state microbatteries suitable for high temperature operation (80-200°C), as power supplies for sensors located in severe environments. The first part of the work will aim at assessing the behaviour (electrochemical cycling, impedance) of conventional Li/LiPON/LiCoO2 microbatteries operating at various temperature, as a function of time, cycles and state-of-charge, in order to determine the level of performance of these devices and to highlight thermally-activated aging phenomena. Then, a thorough physico-chemical characterization of these microbatteries and their constituents will be carried out by various means (STEM-EELS, SEM-FIB, Auger nano-probe, XRD, Raman spectroscopy, XPS, ToF-SIMS,?) in order to identify the origin of these phenomena. The second part of the thesis work will focus on the improvement of the microbattery design - especially by means of a proper choice of electrode and/or electrolyte materials - able to enhance the robustness of the device and to make it more appropriate to specific purposes. Therefore, new thin film electrode/electrolyte materials will be prepared by PVD (sputtering) in a dedicated equipment connected to a glove-box. The thermal stability of these materials will be assessed (DSC, XRD, Raman spectroscopy,?) at first individually, then for couples of electrode/electrolyte materials in order to highlight the possible evolution of their interface (XPS, ToF-SIMS, Auger spectroscopy). Finally, the more promising systems (secondary or primary batteries) will be completed and their electrochemical behaviour at high temperature will be studied. The thesis will be carried out at ICMCB in Bordeaux (Laboratory of Condensed Matter Chemistry) in a joint CEA/CNRS team, having expertise in the fields of all-solid-state microbatteries and thin film materials.

Stretchable conductive hydrogel electrodes for soft tissue stimulation

Département Microtechnologies pour la Biologie et la Santé (LETI)

Laboratoire Chimie des Matériaux et des Interfaces

01-09-2017

SL-DRT-17-0298

isabelle.texier-nogues@cea.fr

The development of biocompatible, flexible and stretchable electronic devices for soft tissue stimulation is a great challenge. The main goal of the PhD is the design and study of new electrode materials which originality lies in the combination of two crosslinked polysaccharide systems incorporating a conducting polymer. These organic conductive tracks will be deposited on stretchable chitosan-PEG films whose mechanical properties can be well controlled. The electrical, mechanical, and structural properties of the materials will be characterized. Their biocompatibility will be assessed by standard assays, and the electrodes will be tested in rodents (targeted application: treatment of chronic back pain). These biocompatible stretchable electrodes will allow for this application to i) improve the lifetime of implants by reducing the risks of material rupture due to fatigue or excessive stretching, ii) improve tissue adhesion to the electrode, and iii) prevent scar tissue formation. In general, such conductive stretchable materials would be of high interest to overcome different challenges (stretchability, flexibility, biocompatibility) in the design of implanted or portable biosensors.

Optimization of the transports in a PEMFC catalyst layer using a modelling/characterization coupled approach : improvement of the catalyst layer performances at high current density

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

01-10-2017

SL-DRT-17-0577

pascal.schott@cea.fr

Decreasing the cost of proton exchange membrane fuel cells (PEMFC) is vital for the ultimate realization of the fuel cell vehicle market. For this challenge, it is essential not only to still reduce the electrode platinum loading but also to maintain a high cathode performance at high-current density. However, even for electrodes made with the most performant catalysts, a large performance loss is observed at high-current density and this loss becomes larger as the Pt loading is lower. In these operation conditions, recent work has shown that this performance loss was predominantly limited by oxygen and proton transport to the catalyst surface. Large progress is expected by the optimization of the electrode microstructure but for this purpose understanding phenomena leading to this large losses becomes critical. To reach this objective, the thesis project will develop a multi-physics model of the active layer, introduced in a multi-scale modelling platform, to improve the geometrical and physical descriptions of matter transport in the electrode. The models will be based on fine microstructure imaging. The originality of this thesis, is the coupling of advanced modeling tools and advanced nano-characterization with the last state of art imaging and methodologies for electrode imaging.

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