Stefano Passerini, Stéphane Laruelle, Michel Armand, Maral Hekmatfar, Sylvie Grugeon, Gebrekidan Gebresilassie Eshetu, R. Jürgen Behm, Thomas Diemant, Helmhotlz Institute of Ulm (HIU), Institute of Surface Chemistry and Catalysis, Universität Ulm - Ulm University [Ulm, Allemagne], Helmholtz Institute Ulm (HIU), Réseau sur le stockage électrochimique de l'énergie (RS2E), Université de Nantes (UN)-Aix Marseille Université (AMU)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Collège de France (CdF (institution))-Université de Picardie Jules Verne (UPJV)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Ecole Nationale Supérieure de Chimie de Paris - Chimie ParisTech-PSL (ENSCP), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Pau et des Pays de l'Adour (UPPA)-Institut de Chimie du CNRS (INC)-Université de Montpellier (UM)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA)-Université Grenoble Alpes (UGA), Laboratoire réactivité et chimie des solides - UMR CNRS 7314 (LRCS), Université de Picardie Jules Verne (UPJV)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Université de Picardie Jules Verne (UPJV)-Institut de Chimie du CNRS (INC)-Aix Marseille Université (AMU)-Université de Pau et des Pays de l'Adour (UPPA)-Université de Nantes (UN)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Ecole Nationale Supérieure de Chimie de Paris - Chimie ParisTech-PSL (ENSCP), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Collège de France (CdF (institution))-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA)-Université Grenoble Alpes (UGA)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM), and Université de Picardie Jules Verne (UPJV)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)
International audience; Aiming at a more comprehensive understanding of the solid electrolyte interphase (SEI) in sodium ion batteries (NIBs), a detailed X-ray photoelectron spectroscopy (XPS) investigation of the few-nanometer thick passivation film formed on hard carbon (HC) in contact with various Na+-ion conducting electrolytes is reported. The electrolytes investigated include 1 M solutions of NaPF6, NaClO4, NaTFSI, NaFSI, and NaFTFSI, all dissolved in a common mixture of ethylene carbonate (EC) and diethylene carbonate (DEC) (EC/DEC = 1/1 wt. ratio). For comparison, the study of analogous Li-based electrolytes containing LiPF6 and LiFSI as representative electrolyte salts is also reported. The anion and cation of the electrolyte salt appear to play a key role in determining the overall SEI layer composition, including its depth evolution and thickness. The SEI building species formed on hard carbon by solvent reduction upon sodiation are found to decrease with the various salts in the order: NaPF6 > NaClO4 ≈ NaTFSI > NaFTFSI > NaFSI. The comparison of lithiated and sodiated HC electrodes shows that the SEI layer is more homogeneous and richer in organic species upon the use of Na-based electrolytes. Surface and depth-profiling XPS analysis on HC electrodes charged in the various electrolyte formulations provides in-depth insights on the differences and similarities of the SEI (composition, thickness, depth evolution, etc.) evolving from the variation in the chemical structure of the cations and anions of the respective salts.