Evaluation of the impact of dry extrusion process on cathode microstructure and performances for polymer-based solid-state batteries
Solid-state batteries (SSB) are expected to outperform standard lithium-ion technology in terms of energy density and safety, with application in electric vehicles or stationary energy storage. Manufacturing of these new battery technologies can rely on existing infrastructure (solvent-based electrode slurry mixing and coating) or need new processing methods. In this context, twin-screw extrusion process exhibits several advantages when applied to SSB, particularly with polymer-based electrolytes.
To speed up the implementation of polymer-based SSB, a better understanding of extrusion process applied to positive electrode manufacturing is needed. The objective of this thesis is to develop new electrode formulations using hot-melt extrusion and understand the impact of process parameters on final performances. It should finally give a clear picture about the advantages and limitations of extrusion compared to standard wet casting.
This PhD project will be part of a collaboration between CEA and Stellantis on the development of new solid-state batteries. The study will focus on the development of extrusion-processed composite electrodes to be used in polymer-based SSB. First, materials will be selected and characterized for a preliminary screening of formulations using lab-scale extrusion. Then, a systematic evaluation of the impact of input materials and operational conditions during extrusion process will be undertaken to highlight the relationships between process, electrode microstructures and performances. Finally, the best performing electrode formulations will be integrated in a fully-extruded prototype and characterized by electrical tests as well as post-mortem analysis.
The PhD candidate will benefit from CEA-LITEN's multidisciplinary environment (Grenoble campus) and Stellantis industrial know-how. Battery Prototyping Platform will be used for extrusion trials and cell assembly, whereas access to advanced characterization equipment (SEM, XPS, rheometers, electrochemical methods, etc.) will guarantee deep understanding of underlying mechanisms.
Advancing Lithium-Sulfur Batteries through the study of the Quasi-Solid Sulfur Conversion
Lithium–sulfur batteries are widely seen as one of the most promising candidates for the next generation of energy storage, offering the potential for significantly higher energy density than today’s batteries while using abundant and inexpensive sulfur. However, several scientific and technological challenges still prevent their large-scale industrial deployment.
One key issue is the formation of soluble lithium polysulfides during battery operation, which can migrate inside the cell and lead to rapid capacity loss. Recent research suggests that a different reaction pathway, known as a “quasi-solid mechanism”, could limit this dissolution and significantly improve battery stability.
This PhD project aims to design and study lithium–sulfur pouch cells operating through this quasi-solid mechanism. The work will combine materials development, electrochemical testing, and advanced characterization techniques to better understand the processes governing battery performance and durability.
The project will focus on two complementary research directions:
1. Design of advanced sulfur cathodes
The first part of the work will involve developing optimized sulfur-based cathodes. This includes exploring different conductive host materials and tuning their structure and surface properties to better confine sulfur and reduce unwanted reactions.
2. Development of improved electrolytes
The second part of the project will focus on electrolyte formulations that reduce the solubility of polysulfides while maintaining good battery performance. Current solutions often rely on dense, fluorinated solvents that increase cost and environmental impact. This project will explore alternative solvent systems and investigate how salt composition and concentration influence cell behaviour.
To gain deeper insight into the quasi-solid reaction mechanism, the project may also involve operando or in-situ characterization techniques, such as Raman spectroscopy, X-ray diffraction, and high-resolution X-ray tomography.
Li alloys for all solid-state batteries with sulfide electrolyte
Using lithium metal as a negative electrode would significantly increase the energy density of current batteries. However, today, this material quickly leads to short circuits during charge/discharge cycles, mainly due to the formation of dendrites and the instability of the interface with the electrolyte. All-solid-state batteries, particularly with sulfide electrolytes, are a promising alternative, but the limitations of lithium metal remain. Lithium alloys appear to be a solution for improving mechanical and interfacial properties while maintaining good energy densities.
The objective of the PhD is to develop and select lithium alloys suitable for sulfide electrolytes batteries, then integrate them into all-solid-state cells in order to study degradation mechanisms. The work will be focused on the synthesis of the alloys, their shaping in thin films and their integration into cells. The alloys will be finely characterized and then electrochemically tested in laboratory cells and pouch cells. Finally, degradation phenomena, particularly at interfaces, will be studied using advanced post-mortem characterizations.
Control & optimization of fuel cell temperature
Proton exchange membrane fuel cells (PEMFC) represent a key technology for the development of clean and sustainable energy systems, particularly for heavy-duty transport applications where their energy density is very attractive. However, in order to represent a viable industrial alternative, a number of obstacles still need to be overcome, including operating costs and, above all, the durability of the systems under real-world conditions. Among the levers for action, optimizing operating conditions is a promising avenue for limiting the degradation phenomena occurring within the cell. The operating temperature is a particularly key parameter because it affects all aspects of the system, from the kinetics of degradation mechanisms to the thermal capacity that the system can dissipate, including the water balance within the fuel cell. Despite the influence of this parameter on durability, it is generally only optimized at the system level to achieve the best performance, the shortest possible response time and to limit the size of the thermal management system.
The aim of this thesis is to work on optimizing the temperature management of a fuel cell within a system, taking into account not only performance but also sustainability criteria. To do this, the impact of operating temperature on degradation mechanisms will be analyzed using various simulation tools already available at LITEN and the teams' fifteen years of experience in studying PEMFC fuel cell degradation. Various thermal architectures will be proposed and evaluated in conjunction with the work on temperature control optimization. The latter will be implemented on a real fuel cell system in order to demonstrate the relevance of the proposed solution using concrete experimental data.
Diphasic thermoregulation system for ultra wide bandgap diamond semiconductors
The objective of this thesis is to study a diphasic thermoregulation system for ultra wide bandgap diamond semiconductors. One of the specific behavior of diamond semiconductors is the negative temperature coefficient of is on-state resistance. The thermoregulation proposed in this thesis aims to optimize the global losses of the system and to insure both temperature and electrical constraints between several diamond semiconductors in parallel.
Based on specifications that will be defined at the beginning of this theses (calories to dissipate, temperature range to control), the PhD candidate will have to:
- Define a temperature control strategy
- Define most appropriate materials and fluid of this system
- Design the thermoregulation system
- Realize and validate experimentally the proposed system
This thesis will tackle numerical simulation (component and thermoregulation system modelling) and experimental tests through the realization of a TRL 3-4 prototype of power converter system integrating diamond Schottky diodes.
The global objective to achieve is to put forward an innovative system modeled and experimentally demonstrated, where control strategy, dimensional and operative elements will be investigated and optimized.
Influence of battery system disassemblability on their environmental impacts
With the rise of electric mobility and Energy storage, the demand for batteries is rapidely increasing. But this growth raises a crucial question: how can we design batteries that are both high-performing, durable, and more environmentaly friendly ?
Without focusing on cell Chemistry, one promising approach lies in disassembly-oriented designs: making battery packs easier to disassemble could facilitate their repair, reuse, or recycling. However, a more easily dismantled design may also increase its mass or reduce the system's reliability, potentially affecting its overall lifetime.
This PhD aims to tackle this challenge by developing an analytical method to link the design of dismountable battery systems with their actual environmental impacts, while explicitly accounting for reliability aspects.
The PhD candidate will assess the ease of disassembly of different battery systems, quantify the environmental gains and losses compared to conventional designs, and help develop a decision-support tool to guide design choices. The proposed research will involve, among other tasks, Life Cycle Assessment (LCA) modelling coupled with battery performance and ageing models, as well as failure probabilities analysis.
This project takes place in a technological context driven by the growing need for resource circularity, the automation of disassembly processes, and the implementation of new European regulations on batteries. If offers a unique opportunity to contribute to the design of the next generation of sustainable battery systems.
Physics-Informed Deep Learning and Multi-Modal Sensor Fusion for Li-Ion and Na-Ion Battery degradation mechanisms predictive monitoring
Context:
Lithium-ion and emerging Sodium-ion batteries are crucial for energy transition and transportation electrification. Ensuring battery longevity, performance, and safety requires understanding degradation mechanisms at multiple scales.
Research Objective:
Develop innovative battery diagnostic and prognostic methodologies by leveraging multi-sensor data fusion (acoustic sensors, strain gauge sensors, thermal sensors, electrical sensors, optical sensors) and Physics-Informed Machine Learning (PIML) approaches, combining physical battery models with deep learning algorithms.
Scientific Approach:
Establish correlations between multi-physical measurements (internal sensors using optical fiber modality, and external sensors Embedded on the cell packaging) and battery degradation mechanisms
Explore hybrid PIML approaches for multi-physical data fusion
Develop learning architectures integrating physical constraints while processing heterogeneous data
Extend methodologies to emerging Na-Ion battery technologies
Methodology:
The research will utilize an extensive multi-instrumented cell database, analyzing measurement signatures and developing innovative PIML algorithms that optimize multi-sensor data fusion and validate performance using real-world data.
Expected Outcomes:
The thesis aims to provide valuable recommendations for battery system instrumentation, develop advanced diagnostic algorithms, and contribute significantly to improving the reliability and sustainability of electrochemical storage systems, with potential academic and industrial impacts.
Innovative techniques for evaluating critical steps and limiting factors for batteries formation
The battery manufacturing sector in Europe is currently experiencing strong growth. The electrical formation step that follows battery assembly and precedes delivery has received little academic attention, despite being crucial for battery performance (lifespan, internal resistance, defects, etc.). It is an essential time-consuming and costly step in the process (>30% of the cell manufacturing cost, and 25% of the equipment cost in a Gigafactory) that would greatly benefit from optimization.
In this thesis, we propose studying battery formation using innovative, complementary, operando non-intrusive techniques. The goal is to identify the limiting mechanisms of the electrolyte impregnation step (filling electrode pores) and of the initial charge. The candidate will implement experimental methods to monitor and analyze these mechanisms. He will also establish a methodology and protocols for studying these steps, combining electrochemical measurements with non-intrusive physical characterizations under operating conditions. The research will focus on optimizing formation time and quality control during this stage.
Understanding the effect of doping on the lifespan of advanced Li-ion battery electrode materials
The development of new electrode materials for Li-ion batteries is primarily focused on two often contradictory objectives: increasing the energy density, and thus the range of vehicles, and reducing the cost of batteries. Disordered NaCl-structured materials, such as Li2MnO2F, thanks to the combination of their Mn-rich, low-cost composition and high Li-ion storage capacity, allow these two aspects to be reconciled. Unfortunately, these materials undergo rapid degradation during cycling, which limits their lifespan. It is therefore necessary to address this degradation to make these materials competitive. Recently, our group has developed a strategy for stabilizing the material by modifying its structure, which is the subject of a patent. The goal of this thesis is to deepen this strategy by improving the understanding of the stabilization mechanism by varying its parameters. The PhD student will have access to all synthesis tools to realize these new materials, as well as electrochemical characterization tools on our battery platform to evaluate their performance. The student will also be required to perform in-depth structural characterizations, notably via various X-ray diffraction methods (including synchrotron).
Direct lithium extraction from brine through adsorption
The development of electric vehicles due to climate and the decision to turn towards a greener energy has increased sharply the demand of lithium over the past decade and will continue to escalate. Thus, lithium extraction projects are proliferating worldwide. Since mining presents a quite highly energy-consuming and polluting solution, alternative lithium sources like brine deposits or seawater are being currently investigated. In this study, we will focus on the approach of a direct lithium extraction from brine sources with different concentrations by adsorption. The first step will be to synthesize and characterize a wide range of materials as adsorbents, from classic oxides (LMO, LTO, etc) to functionalized hybrid porous materials (ZIFs, MOFs, etc). It is also intended to shape these materials with the help of an extruder, in order to enhance performances. Then, these materials will be evaluated both in static and dynamic conditions. Various parameters like the concentration of lithium, the presence of other cations and their concentration will be also evaluated and optimized so that we obtain a facile, efficient and selective process. The results of this study will be valorized through the deposit of patents and the submission of scientific articles along the whole duration of the thesis.