Résumé
We report a systematic investigation of Na-based electrolytesthat comprise various NaX [X=hexafluorophosphate (PF6), perchlorate(ClO4), bis(trifluoromethanesulfonyl)imide (TFSI), fluorosulfonyl-(trifluoromethanesulfonyl)imide (FTFSI), and bis-(fluorosulfonyl)imide (FSI)] salts and solvent mixtures [ethylenecarbonate (EC)/dimethyl carbonate (DMC), EC/diethyl carbonate(DEC), and EC/propylene carbonate (PC)] with respect tothe Al current collector stability, formation of soluble degradationcompounds, reactivity towards sodiated hard carbon (Nax-HC), and solid–electrolyte interphase (SEI) layer formation.Cyclic voltammetry demonstrates that the stability of Al ishighly influenced by the nature of the anions, solvents, and additives.GC–MS analysis reveals that the formation of SEI telltalesdepends on the nature of the linear alkyl carbonates andthe battery chemistry (Li+ vs. Na+). FTIR spectroscopy showsthat double alkyl carbonates are the main components of theSEI layer on Nax-HC. In the presence of Na salts, EC/DMC andEC/DEC presented a higher reactivity towards Nax-HC than EC/PC. For a fixed solvent mixture, the onset temperature followsthe sequence NaClO4<NaFTFSI<NaPF6<NaTFSI<NaFSI, andthe total heat generated increases in the order NaFSI<NaTFSI<NaClO4<NaPF6<NaFTFSI.