Characterization of solid electrolyte interphase on lithium electrodes cycled in ether-based electrolytes for lithium batteries

The electrochemical behavior, chemical composition and the topography of the solid electrolyte interphase (SEI) on lithium electrodes cycling in ether-based electrolytes are investigated using X-ray photoelectron spectroscopy (XPS), scanning probe microscopy (SPM) and electrochemical impedance spectroscopy (EIS). Electrolytes with ethers (1,2-Dimethoxyethane (DME), Diethylene glycol dimethyl ether (DG) and Triethylene glycol dimethyl ether (TEGDME)) are employed to understand the effect of ether/alkyl moieties ratio on the formation of the SEI films. The cycling behavior and impedance spectra of the symmetrical cells show that the stability and property of those SEI films depend on the selection of the solvent. The results indicate that DG and TEGDME based electrolytes lead to a higher resistance for lithium ion migration through the SEI film. Combined with XPS spectra and depth profile, different chemical composition and depth profile distribution for those SEI films are observed. This difference could be attributed to the decomposition of the electrolytes with different ethers. The height images and phase images obtained from SPM show that the decomposition of the three solvents on lithium metal is active after the immersion of the lithium electrodes in electrolytes. In contrast, the decomposition of TFSI− from lithium salt is more active during the cycling of the cells.