Understanding the solid electrolyte interphase (SEI) in lithium batteries is very important to face the major safety issue of lithium dendritic growth during battery charge. The aim of this work is to study the thickness and the chemical nature of the SEI by XPS, as well as their influence on the electrochemical performance of the battery for different liquid organic electrolytes. XPS imaging is also used in this work to get a chemical mapping of the SEI layer components formed on the metallic lithium electrode surface cycled in different conditions. Data processing based on the principal component analysis (PCA) method has been conducted in order to illustrate the SEI layer heterogeneities. The obtained results are compared with energy-dispersive X-ray spectroscopy (EDX) mapping. Thereby, the benefits and the precision of the XPS imaging technique to identify chemical compounds distribution have been highlighted. These different analyses have led to a better knowledge of the redox processes occurring at the top surface of lithium metal electrodes cycled in different liquid electrolytes.

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The lithium and lithium-ion battery electrode chemical stability in the pristine state has rarely been considered as a function of the binder choice and the electrode processing. In this work, X-ray photoelectron spectroscopy (XPS) and XPS imaging analyses associated with complementary Mössbauer spectroscopy are used in order to study the chemical stability of two pristine positive electrodes: (i) an extruded LiFePO4-based electrode formulated with different polymer matrices [polyethylene oxide and a polyvinylidene difluoride (PVdF)] and processed at different temperatures (90 and 130 °C, respectively) and (ii) a Li­[Ni0.5Mn0.3Co0.2]­O2 (NMC)-based electrode processed by tape-casting, followed by a mild or heavy calendering treatment. These analyses have allowed the identification of reactivity mechanisms at the interface of the active material and the polymer in the case of PVdF-based electrodes.