Lithium metal batteries (LMB) are regarded as the potential holy grail in battery research, due to the high theoretical specific capacity of the lithium metal anode (3860 mAh g-1).[1] The performance and lifetime of LMBs utilizing state-of-the-art aprotic nonaqueous electrolytes is significantly impacted by the characteristics of the solid electrolyte interphase (SEI) formed on the surface of lithium metal electrodes, which regulates crucial battery lifetime impacting parameters, e.g. lithium stripping/plating behaviour, dendrite growth and in operando electrolyte consumption.[2] One of the main approaches to advance the SEIs characteristics addresses the optimization of the electrolyte formulation[3] by the variation of its main components, co-solvents, conducting salts and functional additives. The formation of an uncontaminated preformed SEI on a lithium metal electrode, utilizing a recently established method using in-house build devices,[4] enables an unfiltered few on the SEIs characterises, e.g. chemical composition, SEI resistance, influence on dendrite growth and homogeneous stripping and plating behaviour. We herein present the systematic overview on the enhancing or inhibiting effects on those characterises by multiple selected additives (vinylene carbonate (VC), fluoroethylene carbonate (FEC), lithium nitrate (LiNO3), lithium difluorophosphate (LiDFP)) and two conducting salts (lithium hexafluorophosphate (LiPF6), lithium(bisfluorosulfonyl)imid (LiFSI)) in an organic carbonate-based electrolyte (EC/EMC 3:7 by wt.). The characteristics were analyzed by means of stripping/plating experiments, EIS (in operando), SEM (incl. post mortem), and XPS (incl. post mortem) methods, as well as galvanostatic cycling in NMC811||Li cells.
The obtained results clearly highlight the importance of sorrow systematic investigation and establish the formation of an uncontaminated SEI as a powerful tool to elucidate the cause and effect of different electrolyte components on the SEIs formation and characteristics, ultimately significantly impacting the research towards enhanced and reliable LMB performance.

References:
[1] D. Jin, J. Park, M. H. Ryou, Y. M. Lee, Adv. Mater. Interfaces 2020, 7, 1–17.
[2] B. Horstmann, J. Shi, R. Amine, M. Werres, X. He, H. Jia, F. Hausen, I. Cekic-Laskovic, S. Wiemers-Meyer, J. Lopez, D. Galvez-Aranda, F. Baakes, D. Bresser, C.-C. Su, Y. Xu, W. Xu, P. Jakes, R.-A. Eichel, E. Figgemeier, U. Krewer, J. M. Seminario, P. B. Balbuena, C. Wang, S. Passerini, Y. Shao-Horn, M. Winter, K. Amine, R. Kostecki, A. Latz, Energy Environ. Sci. 2021, 14, 5289–5314.
[3] M. Ue, K. Uosaki, Curr. Opin. Electrochem. 2019, 17, 106–113.
[4] Manuscript under preparation.