Effects of the Electrolyte Concentration on the Nature of the Solid Electrolyte Interphase of a Lithium Metal Electrode

Abstract

The need of more powerful systems with higher energy density raises a lot of interest in lithium metal batteries (LMBs). As LMBs suffer from safety concerns due to the dendrite growth, several strategies have been studied to limit this growth. Using a highly concentrated electrolyte allows a homogeneous lithium plating that delays the formation of dendrites. Herein, different techniques are used in order to better understand the beneficial role of the salt concentration in the lithium plating/stripping. Operando Fourier transform infrared spectroscopy highlights the better reversibility of the Li+ solvation in the 5 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in 1,2‐dioxolane/1,3‐dimethoxyethane electrolyte in comparison with the 1 M electrolyte. This obviously leads to different electrolyte decompositions during the lithium plating/stripping and changes the nature of the electrode solid electrolyte interphase (SEI) depending on the salt concentration. Gas chromatography coupled with mass spectrometry as well as X‐ray photoelectron spectroscopy confirms that with the 5 M LiTFSI electrolyte the salt is preferentially reduced during the plating/stripping, leading to a more inorganic SEI on the lithium metal electrode.

Additive-Driven Nanoscale Architecture of Solid Electrolyte Interphase Revealed by Cryogenic Transmission Electron Microscopy

“…According to the reference, it is reported that the NO 3 – anion enhances the ion–dipole interaction between Li + –DME, which conversely leads to weakening of Li + –anion (FSI – ) interactions . The enhanced interaction between Li + –DME can be confirmed by the stretching vibration peak of the DME solvent (C–O–C) in the Raman spectrum . Considering that the blue shift of the DME peak means a stronger Li + –DME interaction, the largest blue shift in BE-N (Figure S7) compared to BE reveals the strengthened ion–dipole interaction of the Li ion with the DME solvent.…”

Compositionally Sequenced Interfacial Layers for High‐Energy Li‐Metal Batteries

“…Low reactivity was observed between the solvent molecules and Li‐metal electrode in electrolytes with a high salt concentration owing to the presence of inorganic SEI species formed by the decomposition of salt. [ 19 , 20 , 21 , 22 , 23 , 24 ] Additionally, localized highly concentrated electrolytes (LHCEs), which are achieved by incorporating fluorinated solvents into highly concentrated electrolytes (HCEs), overcome the intrinsic limitations of HCEs such as high viscosity and poor wettability. [ 25 , 26 , 27 , 28 ] LHCEs increase the proportion of cation‐anion aggregate species in the solvation structure of the electrolyte and aid in the construction of an anion‐driven SEI on the Li‐metal anode (Figure S1 , Supporting Information).…”