Development of laser-induced breakdown spectroscopy for Li-Ion battery materials

The growing demand for sustainable energy technologies and the shift toward electric mobility highlight the need for efficient and durable energy storage systems. Lithium-ion batteries (LIBs) currently dominate this field due to their high energy density and long cycle life, but their performance is limited by interfacial degradation processes that reduce capacity and shorten lifetime. The high-voltage spinel LiNi₀.₅Mn₁.₅O₄ (LNMO) is a promising positive electrode material, but it suffers from electrolyte decomposition and manganese dissolution at high voltage values. Protective surface coatings, particularly those deposited by atomic layer deposition (ALD), offer an effective strategy to mitigate these issues while maintaining ionic conductivity. In this context, laser-induced breakdown spectroscopy (LIBS) emerges as a powerful tool for fast, spatially resolved elemental analysis of electrode surfaces. This thesis explores the use of LIBS on post-mortem lithium foils to study the dissolution of manganese from the LNMO positive electrode to the lithium negative electrode. This work was conducted in the battery laboratory in Pessac (France) of CEA Tech Nouvelle-Aquitaine. The LIBS equipment is integrated in an argon-filled glovebox to allow lithium handling. Since the system was new, this work also included the calibration of the instrument and optimization of operating parameters, such as laser energy. LIBS craters on silicon wafer and lithium foil were studied using scanning electron microscope and confocal microscope to evaluate ablation conditions, which reflect the quality of spectral acquisition. Lithium fluoride thin films deposited on silicon wafer by ALD were analysed by LIBS to build calibration curves for two emission lines of lithium and to determine the corresponding limit of detection. After this calibration procedure which provided a better knowledge of the equipment, post-mortem analysis of negative electrodes was used to evaluate ALD-deposited coatings on LNMO positive electrodes. In particular, the influence of lithium fluoride coating on suppressing Mn dissolution was evaluated at different cut-off voltages (between 4.2 V and 5.0 V), and two additional coatings—lithium phosphate and lithium borate—were examined under the most critical condition of 5.0 V. To the best of our knowledge, this study represents the first use of LIBS for post-mortem Li metal foils. The methodological development carried out here enabled reliable mapping of the electrode surface and detection of manganese even at very low concentrations. Overall, the results provide new insights into the effectiveness of protective coatings on LNMO and demonstrate the potential of LIBS as a sensitive analytical tool for the post-mortem characterization of battery electrodes.