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.

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