Soutenance thèse Xavier Moine
M Xavier Moyne soutiendra sa thèse intitulée "Contribution à l’élaboration d’une électrode de référence fiable et durable pour le suivi du lithium plating lors du vieillissement des batteries"
| The rapid growth of electric mobility continues to drive demand for high-performance lithium-ion batteries (LiBs). Thanks to their high energy density, long lifetime, and technological maturity, LiBs have become the dominant energy-storage technology for electric vehicles (EVs) and a cornerstone of global decarbonization efforts. As EV adoption accelerates, further improvements in fast-charging capability and usable capacity are needed to remain competitive while ensuring long-term durability. Addressing these challenges requires advanced diagnostic approaches capable of providing detailed insight into electrode-level processes during battery operation. Current strategies for ultra-fast charging in EVs rely on power maps implemented within the battery management system, which define the maximum charging current that can be safely applied without inducing excessive degradation. The development of these power maps often relies on three-electrode measurements, where a reference electrode (RE) enables direct and current-independent monitoring of the individual electrode potentials during operation. This capability is essential for accurately defining the safe operating potential windows of both electrodes and preventing excursions into conditions associated with accelerated ageing mechanisms, such as lithium plating, electrolyte oxidation, and structural degradation. Despite these advantages, the implementation of REs in practical battery cells remains challenging. Previous studies have reported limited long-term stability of REs, restricting their application in ageing investigations. Furthermore, the presence of a RE can perturb ionic transport pathways and current distribution within the cell compromising measurement accuracy. To address these limitations, an innovative four-electrode cell architecture was developed in this work. The proposed design enhances the long-term stability of the RE while enabling periodic verification of its electrochemical potential to ensure measurement reliability. Using this approach, stable operation was demonstrated over 200 cycles at C/5 with a maximum potential drift of only 5 mV. The influence of a mesh-shaped RE on cell behavior was subsequently investigated using operando X-ray diffraction (XRD) at the European Synchrotron Radiation Facility (ESRF). The results revealed a modest increase in graphite lithiation heterogeneity, corresponding to a maximum lithiation difference of approximately Δx ≈ 0.10 at C/5 and Δx ≈ 0.13 at C/3. Importantly, the LiC6 phase was consistently detected through both electrochemical measurements and structural analysis, indicating the absence of significant measurement artefacts induced by the RE. The study further demonstrated that positioning the RE outside the electrochemically core leads to inaccurate potential measurements, as the outside RE preferentially probes the graphite overhang rather than the representative electrode region. The feasibility of monitoring lithium plating using operando synchrotron XRD was then demonstrated. The technique successfully captured the onset, growth, and subsequent consumption of metallic lithium during cycling. In particular, combining lithium quantification from XRD measurements, local graphite activity, and RE measurements provided a robust framework for identifying lithium plating under fast-charging conditions. Finally, the four-electrode system was implemented in commercial 1 Ah cells to evaluate its scalability and relevance to practical battery systems. |
Infos lieu
La thèse se déroulera le vendredi 27 novembre 2026 à 9 h, Amphi E du bâtiment E de l'Ensimag, 681 rue de la Passerelle, 38400 Saint-Martin-d'Hères