High-throughput experimentation applied to battery materials
High throughput screening, which has been used for many years in the pharmaceutical field, is emerging as an effective method for accelerating materials discovery and as a new tool for elucidating composition-structure-functional property relationships. It is based on the rapid combinatorial synthesis of a large number of samples of different compositions, combined with rapid and automated physico-chemical characterisation using a variety of techniques. It is usefully complemented by appropriate data processing.
Such a methodology, adapted to lithium battery materials, has recently been developed at CEA Tech. It is based, on the one hand, on the combinatorial synthesis of materials synthesised in the form of thin films by magnetron cathode co-sputtering and, on the other hand, on the mapping of the thickness (profilometry), elemental composition (EDS, LIBS), structure (µ-DRX, Raman) and electr(ochim)ical properties of libraries of materials (~100) deposited on a wafer. In the first phase, the main tools were established through the study of Li(Si,P)ON amorphous solid electrolytes for solid state batteries.
The aim of this thesis is to further develop the method so as to enable the study of new classes of battery materials: crystalline electrolytes or glass-ceramics for Li or Na, oxide, sulphides or metal alloys electrode materials. In particular, this will involve taking advantage of our new equipment for mapping physical-chemical properties (X-ray µ-diffraction, Laser-Induced Breakdown Spectroscopy) and establishing a methodology for manufacturing and characterising libraries of thin-film all-solid-state batteries. This tool will be used to establish correlations between process parameters, composition, structure, and electrochemical properties of systems of interest. Part of this work may also involve data processing and programming the characterisation tools.
This work will be carried out in collaboration with researchers from the ICMCB and the CENBG
Study of grayscale photoresists and lithography process optimizations for submicron optical applications
Grayscale lithography process has been used for several years to obtain complex tridimensional structures on semiconductors substrates. This process is particularly adapted for optical and opto-electronics applications.
CEA-LETI has developed a strong expertise on I-line (365nm) grayscale lithography, and is now willing to expand its capabilities and explore grayscale process with DUV (248nm and 193nm) lithography. The objective is to be able to obtain complex 3D structures with critical dimensions less than 1µm.
This PhD work will focus on acquiring a better understanding of the chemical and physical phenomena involved in grayscale photoresists, allowing the optimization of lithography processes. This work will also help with the development of etching processes and new optical models for mask designs.
You will join the lithography team of CEA-LETI, and you will exchange as well with other teams working on this topic (etching, optical simulation). You will have access to a wide range of state of the art equipments installed in LETIs cleanrooms, as well as a world class nanocharacterization platform (PFNC).
Eco-designed materials for encapsulating new-generation flexible photovoltaic modules
The lifetime of thin-film devices such as Organic Photovoltaic (OPV) devices or new-generation lightweight and/or flexible Silicon (Si) photovoltaic modules is critical to their commercialization. In particular, it is crucial to encapsulate them with highly gas-barrier materials to avoid degradation through various water/oxygen insertion mechanisms that can be coupled to illumination. This objective is all the more complex when the device and its encapsulation need to be flexible. Moreover, the eco-design of this new generation of flexible modules raises the question of the nature of the encapsulation materials used, as well as that of the end-of-life of the materials making up the modules. For example, the current use of fluorinated polymers for encapsulation generates toxic products at end-of-life, and could be replaced by the use of eco-designed materials, potentially bio-sourced, if the performance is adapted to the photovoltaic technology employed and the use.
The aim of this thesis will be to study the physico-chemical properties (gas barriers, mechanical, thermal, etc.) of bio-sourced encapsulants developed as part of a national PEPR BioflexPV project. These studies will cover both sealing materials and flexible caps. In addition, these materials will be used to encapsulate real OPV and flexible Si devices, in order to study their degradation under different illumination, temperature and humidity conditions. These studies will help define the degradation mechanisms involved, depending on the photovoltaic technology used (OPV or Si), and thus define the desired properties for bio-sourced encapsulants.
Development of high-halogen argyrodites for all-solid all-sulfide battery
All-solid-state batteries have been enjoying renewed interest in recent years, as this technology offers the prospect of higher energy densities due to the use of lithium as a negative electrode, as well as increased battery safety compared with Li-ion technology. The use of sulfides as positive electrode materials coupled with argyrodite as solid electrolyte are interesting systems to develop. The argyrodites achieve ionic conductivities close to those of liquid electrolytes. Moreover, the electrochemical stability window of sulfides is close to that of argyrodite, making all-sulfide technology a promising one for the development of all-solid batteries.
In order to improve the conduction properties of argyrodites, recent studies have shown that ionic conductivity is highly dependent on their local structure. Solid-state NMR thus appears to be a promising technique for probing the local environments of the nuclei mentioned, and in particular for quantifying the variety of different local environments favoring an increase in ionic conductivity. Some compositions enriched in halides appear to promote ionic conduction, and the synthesis of corresponding materials and their structure will be studied.
The thesis will focus on two main areas: the study of all-sulfide batteries and the fine characterization of argyrodite with controlled local structures. Halogen-rich argyrodites will be developed and studied to determine the influence of different local environments on conduction properties.
Numerical twin for the Flame Spray Pyrolysis process
Our ability to manufacture metal oxide nanoparticles (NPs) with well-defined composition, morphology and properties is a key to accessing new materials that can have a revolutionary technological impact, for example for photocatalysis or storage of energy. Among the different nanopowders production technologies, Flame Spray Pyrolysis (FSP) constitutes a promising option for the industrial synthesis of NPs. This synthesis route is based on the rapid evaporation of a solution - solvent plus precursors - atomized in the form of droplets in a pilot flame to obtain nanoparticles. Unfortunately, mastery of the FSP process is currently limited due to too much variability in operating conditions to explore for the multitude of target nanoparticles. In this context, the objective of this thesis is to develop the experimental and numerical framework required by the future deployment of artificial intelligence for the control of FSP systems. To do this, the different phenomena taking place in the synthesis flames during the formation of the nanoparticles will be simulated, in particular by means of fluid dynamics calculations. Ultimately, the creation of a digital twin of the process is expected, which will provide a predictive approach for the choice of the synthesis parameters to be used to arrive at the desired material. This will drastically reduce the number of experiments to be carried out and in consequence the time to develop new grades of materials
Development of a multiphysics stochastic modelling for liquid scintillation measurements
The Bureau international des poids et mesures (BIPM) is developing a new transfer instrument named the "Extension of the International Reference System" (ESIR), based on the Triple-to-Double Coincidence Ratio (TDCR) method of liquid scintillation counting with a specific instrumentation comprising three photomultipliers. The aim is to enable international comparisons of pure beta radionuclides, certain radionuclides that decay by electron capture, and to facilitate international comparisons of alpha emitting radionuclides.
The TDCR method is a primary activity measurement technique used in national laboratories. For the activity determination, its application relies on the construction of a model of light emission requiring knowledge of the energy deposited in the liquid scintillator. Depending on the decay scheme, the combination of different deposited energies can be complex, particularly when it results from electronic rearrangement following electron capture decay. The stochastic approach of the RCTD model is applied by randomly sampling the different ionizing radiation emissions following a radioactive decay. The recent addition of modules for automatically reading nuclear data (such as those available in the Table des Radionucléides) in radiation/matter simulation codes (PENELOPE, GEANT4), means that all possible combinations can be rigorously taken into account. The stochastic approach makes it possible to consider the actual energy deposited in the liquid scintillation vial, taking into account interactions in the instrumentation as a whole.
The aim of this thesis is to develop a multiphysics stochastic approach using the GEANT4 radiation/matter simulation code, to be applied in particular to the BIPM's ESIR system. The choice of the Geant4 code offers the possibility of integrating the transport of ionizing particles and scintillation photons. This development is of great interest for radioactivity metrology, with the aim of ensuring metrological traceability to a larger number of radionuclides with the BIPM's ESIR system. The thesis will be carried out in collaboration with the Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA), which already has experience in developing a stochastic model with the GEANT4 code for its instrumentation dedicated to the TDCR method at the Laboratoire National Henri Becquerel (LNE-LNHB).
Dynamic Assurance Cases for Autonomous Adaptive Systems
Providing assurances that autonomous systems will operate in a safe and secure manner is a prerequisite for their deployment in mission-critical and safety-critical application domains. Typically, assurances are provided in the form of assurance cases, which are auditable and reasoned arguments that a high-level claim (usually concerning safety or other critical properties) is satisfied given a set of evidence concerning the context, design, and implementation of a system. Assurance case development is traditionally an analytic activity, which is carried out off-line prior to system deployment and its validity relies on assumptions/predictions about system behavior (including its interactions with its environment). However, it has been argued that this is not a viable approach for autonomous systems that learn and adapt in operation. The proposed PhD will address the limitations of existing assurance approaches by proposing a new class of security-informed safety assurance techniques that are continually assessing and evolving the safety reasoning, concurrently with the system, to provide through-life safety assurance. That is, safety assurance will be provided not only during initial development and deployment, but also at runtime based on operational data.
Hyperpolarized Xenon NMR to probe the functionality of biological barriers
Optical pumping of xenon, giving rise to an intense NMR signal, is a specialty of the LSDRM team. Xenon, which is soluble in biological media, has a wide range of chemical shifts, which we use here to study the properties of cell barriers. Numerous pathologies stem from an alteration of these barriers.
In this thesis, we aim to develop a specific methodology using hyperpolarized xenon to study the functionality (integrity, permeability, selectivity) of biological barriers, using in vitro and in vivo spectroscopy and imaging. The thesis will be divided into two parts: in vitro, the aim will be to develop a device and NMR protocols for studying model cell assemblies; in vivo, studies on rodents will enable us to assess xenon's ability to reach organs more or less close to the lungs while maintaining its polarization, and to measure kinetics across barriers. This topic will enable major instrumental and methodological advances, as well as a deepening of our knowledge of selective transport processes at different biological barriers.
Development of a Multilayer Encapsulation System for the Production of Core-Shell Microcapsules Suitable for Organoid Growth
Every year, 20 million people worldwide are diagnosed with cancer, with 9.7 million succumbing to the disease (Kocarnik et al., 2021). Personalized treatment could significantly reduce the number of deaths. This thesis addresses this challenge by proposing the development of organoids derived from patient biopsies to optimize treatments.
The bioproduction of encapsulated cells in biopolymers is a rapidly growing field, with applications in personalized medicine, research, drug screening, cell therapies, and bioengineering. This thesis aims to contribute to these fields by focusing on the multilayer encapsulation of cells in biopolymers with a wide range of viscosities.
The inner layer (core) provides an optimal environment for the maturation and survival of cells or organoids, while the outer layer (shell) ensures mechanical protection and acts as a filtering barrier against pathogens.
This new thesis aims to design, develop, and study—both analytically and numerically—the architecture of a dual-compartment nozzle for the high-frequency production of monodisperse core-shell capsules. It builds upon a previous thesis completed in 2023, which focused on the detailed characterization and development of a predictive model for the generation of single-layer microcapsules using centrifugal force alone.
The formation and ejection mechanisms of multilayer capsules are complex, involving the rheological properties of biopolymers, centrifugal force, surface tension, and interfacial dynamics. The nozzle architecture must account for these properties.
The first part of this thesis will focus on understanding the multilayer formation and ejection mechanisms of microcapsules as a function of nozzle geometry. This will allow the prediction and control of capsule formation based on the rheological properties of the biopolymers. The second part will involve developing an automated system for the aseptic production of capsules. Finally, biological validation will assess the functionality and reliability of the developed technology.
To achieve the objectives of this study, the candidate will first conduct analytical and numerical studies, design the ejection nozzles, and leverage the laboratory's expertise for their fabrication. Fluidic tests on prototypes will help optimize the design, leading to the development and testing of a fully operational microcapsule production system.
The ideal candidate will have a background in physics, engineering, and fluid mechanics, with a strong inclination for experimental approaches. Prior experience in microfluidics or biology would be a valuable asset.
All solid-state lithium batteries based on Pyrochlore solid electrolyte
Due to the increasing energy demand, developing efficient storage systems, both stationary and portable, is crucial. Among these, lithium-ion batteries stand out as the most advanced, capable of being manufactured using liquid or solid electrolytes. All-solid-state batteries have a bright future thanks to their non-flammable electrolytes and their ability to use metallic lithium to increase energy density. Although research on these batteries is dynamic, their commercialization is not yet a reality. Indeed, two significant obstacles to their development remain: the low intrinsic ionic conductivity of solids and the difficulty of obtaining good solid/solid interfaces within the composite electrodes and the complete system.
This thesis explores the potential of pyrochlore oxyfluoride as a new class of superionic material for all-solid-state batteries, which are more stable in air and have higher ionic conductivity than current solid oxide electrolytes. The electrochemical properties of all-solid-state batteries will be carefully examined using a combination of in situ and operando techniques, such as XRD, Raman, ion beam/synchrotron analysis, solid-state NMR, X-ray tomography, etc.
Keywords :
Solid electrolyte, All-solid battery, Nuclear magnetic resonance, Electrochemistry, Pyrochlore Oxyfluoride, in situ/operando, Spectroscopy, Synchrotron