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.
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.
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.
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.
Characterisation of reaction pathways leading to thermal runaway for new battery technologies
The development of all-solid-state cells is no longer a mere hypothesis today. As part of the Safelimove project, we assessed the safety of hybrid polymer cells of 1 Ah and 3 Ah, which led to a publication. Additionally, within the Sublime project, we evaluated the safety of 1 Ah sulfide-based cells (argyrodite), and a publication is currently being submitted.
With the arrival of these new cells, it becomes even more crucial to support their development with a detailed safety assessment and the identification of the complex mechanisms involved. Large-scale instruments such as synchrotrons and neutron reactors offer a powerful opportunity to achieve this goal, as they provide the best spatial and temporal resolutions. For example, thanks to fast X-ray radiography at ESRF, it is possible to visualize the inside of a cell during thermal runaway, thereby identifying the local impact of (electro)chemical reactions on the microstructure of components and validating our thermal runaway models. Moreover, with wide-angle X-ray scattering (WAXS), it is possible to monitor in situ the evolution of the crystalline structure of active materials during a very rapid thermal runaway reaction. Indeed, synchrotron radiation allows the acquisition of one diffractogram every 3 milliseconds. The neutron beam at ILL also enables us to track the evolution of lithium metal structure before, during, and after runaway. It is important to emphasize that these three techniques are currently mastered by the LAPS teams and have already led, or will lead, to publications.
Furthermore, new complementary techniques may be explored, such as studying the impact of thermal/mechanical stress on active materials using the BM32 beamline, or evaluating the oxidation states of metals via X-ray absorption spectroscopy (XAS) on ID26.
More conventional laboratory characterizations will also be carried out, such as DSC, TGA-MS, and XRD.
As part of our various collaborations, for the all-solid-state system, the active material of the positive electrode will most likely be NMC, or even LMFP in the event of supply difficulties. The electrolyte used will be sulphide-based, or even halide-based, while the anode will be composed of lithium metal or even a lithium alloy. If time permits, a post-Na-ion system will be considered from the second year onwards. Among other things, the thesis will aim to identify, based on the materials used, whether there are reactions prior to cathode destabilisation, whether the solid electrolyte reacts with the oxygen in the cathode or with the anode material, and whether these parallel reactions contribute to better or worse cell safety.
The three years of the PhD will be structured as follows: the first year will be dedicated to a literature review and the characterization of sulfide technology. Following the first milestones (1st CSI) and the evaluation of ongoing work on sulfides, the second year will focus either on sodium-ion technology or on further development of sulfide technology. Finally, the third year, in addition to the thesis writing, will concentrate more specifically on the impact of the identified materials on safety.
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.
Fast charging of lithium-ion batteries : Study of the lithium plating phenomenon using operando NMR
The focus of the thesis is the fast-charging process of lithium-ion batteries and, more specifically, the phenomenon of lithium plating, which will be studied using operando NMR. The target application is electric mobility. The objective of the thesis is to study the dynamics of lithium insertion and lithium metal deposition at the graphite or graphite/silicon-based negative electrode in order to understand the mechanisms leading to plating formation.
Operando NMR is an ideal technique for this study because it offers the unique possibility of simultaneously tracking the signals of the lithiated graphite phases and of deposited lithium during the electrochemical processes. The coupling of electrochemistry and operando NMR will allow us to determine the onset of plating, i.e. the potential of the negative electrode at which deposition begins, and the kinetics of lithium metal deposition and reinsertion at different temperatures and different charging current regimes. We will study Li-ion batteries with a pure graphite negative electrode, but also with graphite-silicon electrodes, in order to investigate the impact of silicon on this phenomenon. The data obtained on the onset mechanisms and the kinetics of lithium metal deposition and reinsertion will be used in a multiphysics model that has already been developed in the laboratory to improve the prediction of plating onset. We will then be able to evaluate the chargeability gains on an NMC 811 // Gr+Si system incorporating optimized electrodes and propose innovative charging protocols.
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).