Back to the basics: Advanced understanding of the as-defined solid electrolyte interphase on lithium metal electrodes

• DOI: 10.1016/j.jpowsour.2022.232118
• Publication Date: 2022-09-26T04:19:31Z
• Authors: Sebastian P. Kühn; Felix Pfeiffer; Marlena Bela; Uta Rodehorst; Dominik Weintz; Marian Stan; Masoud Baghernejad; Martin Winter; Isidora Cekic-Las...
• Keywords: Passivation; Interphase; Lithium carbonate; Lithium metal

The design and control of the solid electrolyte interphase (SEI) is essential for the implementation ofrechargeable lithium metal based batteries and has been a major research theme of lithium metal electrodes forover 50 years. However, research on an as-defined SEI is challenging due to the inevitable presence of a nativepassivation layer (NPL), commonly contaminating an in situ formed SEI and its characteristics. Herein we presentan original study on an uncontaminated SEI being an exclusive reaction product of lithium and a liquid aproticelectrolyte, highlighting the largely negative influence of the NPL on different SEI characteristics and functionaladditive evaluation. A preformed as-defined SEI (pSEI) was generated by an in-house designed advanced pretreatmentmethod, ensuring high reproducibility and exclusion of the NPL by cutting and pressing lithiummetal in solution/electrolyte. The implementation of a pSEI allows for a systematic study and an uncloudedcomparison of the two common functional additives vinylene carbonate (VC) and fluoroethylene carbonate (FEC)in an equal molar setting. The introduction of an as-defined SEI allowed to clearly distinguish between enhancinginfluence on the SEI characteristics and full cell performance by FEC and the largely negative effect of VC ondifferent SEI characteristics.