Physico-Chimie de la Matière Condensée

• Development of an innovative method of abusive nail testing in order to be representative of an internal short circuit of a Lithium-ion element.

  by Jordan SETTA (ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux)

  The defense will take place the 21-07-2026 at 13h30 - Salle Campanule Institut National de l'Environnement Industriel et des Risques (INERIS), Parc technologique Alata, 5 Rue Jacques Taffanel, 60550 Verneuil-en-Halatte

  in front of the jury composed of

  • Dany CARLIER-LARREGARAY - Professeure des universités - Université de Bordeaux - Directeur de these
  • Rémi VINCENT - Ingénieur de recherche - CEA - Rapporteur
  • Sara ABADA - Ingénieure de recherche - IFP Energies nouvelles - Examinateur
  • Cyril AYMONIER - Directeur de recherche - CNRS - Examinateur
  • Jean-Michel VINASSA - Professeur des universités - Bordeaux INP - Examinateur
  • Marcos BATISTELLA - Maître de conférences - IMT Mines Alès - Rapporteur

  Summary

  This thesis focuses on understanding the physical, electrical, and thermal mechanisms governing the initiation, persistence, and extinction of internal short circuits induced by nail penetration in lithium-ion batteries. This work presents a state of the art dedicated to lithium-ion batteries and internal short circuits. The different types of defects, their origins, and their thermal and safety-related consequences are detailed. A critical review of the experimental methods previously reported in the literature is also provided. In order to investigate the impact of internal short circuits on lithium-ion batteries. A dedicated nail penetration setup was designed to ensure precise control of the experimental parameters while enabling simultaneous acquisition of electrical and thermal quantities. The influence of mechanical parameters - penetration speed, nail diameter, and nail tip angle - was investigated in order to optimize test reproducibility. The results show that nail geometry strongly affects contact resistances, current intensity, and heat generation. Post-mortem analyses based on the controlled separation of electrode active materials were also developed, particularly using microscopy techniques, in order to identify contact areas and associated degradations. Experiments performed in dry stacks reveal several regimes depending on the nature of the electrodes in contact and on the local resistivity of the defect. A comparative study between different stack architectures shows that stack geometry (particularly electrode thickness) influences both short-circuit stability and thermal dissipation. The work also highlights “fuse-like” behaviors leading to spontaneous extinction of the defect, and a threshold resistivity value was experimentally estimated. Tests conducted in the presence of an electrolytic solvent without lithium salt reveal modifications of heat transfer and contact resistances, as well as cathode degradation. Finally, experiments conducted on active cells show significantly higher thermal rises due to additional electrochemical phenomena. The influence of penetration location and state of charge on defect severity was also demonstrated. This work also investigates the relative contribution of anodes, cathodes, and separators. Anodic configurations (Anode-Separator-Anode) lead to the most severe regimes, associated with high currents and significant temperature rises, while cathodic configurations (Cathode-Separator-Cathode) mainly exhibit transient “fuse-like” behavior events. Laboratory-scale electrodes were fabricated, including configurations reversing the conventional material arrangement: anodic active material coated onto an aluminum current collector, and cathodic active material coated onto a copper current collector. Experiments performed on these configurations confirm that the active material primarily governs the short-circuit dynamics, while the influence of the current collector appears as a second-order effect. Finally, morphological, thermal, and thermo-mechanical analyses of separators demonstrate that their properties play a key role in maintaining or extinguishing the short circuit by locally preserving the electrical insulation between electrodes. Overall, this work contributes to a better understanding of internal short-circuit mechanisms in lithium-ion batteries and provides key insights for improving battery safety, designing cells that are more robust against mechanical and thermal abuse, and developing strategies to prevent critical failures.