First-Principles Studies on the Structure and Stability of the Solid Electrolyte Interphase with LiPON in Solid-State Batteries

The formation of a solid–electrolyte interphase (SEI) resulting from the decomposition of the solid electrolyte in contact with an alkali metal significantly influences battery performance. Despite extensive research on the SEI’s chemical composition and distribution, its atomic-level structure and stability remain poorly understood. This study employs first-principles calculations to investigate the stability of all possible interfaces formed during the decomposition of lithium phosphorus oxynitride (LiPON) upon contact with lithium metal. A systematic analysis identified the following interfacial stability sequence: Li2O/Li3N > Li2O/Li3P ≈ Li2O/Li3PO4 > Li2O/1D-LiPON. Interestingly, for interfaces involving solely Li3N, the observed trend is Li3N/Li3P > Li3N/Li3PO4 > Li3N/1D-LiPON. Additionally, Li3P-based interfaces exhibit a trend of Li3P/Li3PO4 > Li3P/1D-LiPON. These results suggest that the SEI between LiPON and lithium metal exhibits a distribution composed of Li∥Li2O∥Li3N∥Li3P∥Li3PO4∥LiPON. This systematic analysis offers valuable insights into the relative stability of interfaces formed between LiPON decomposition products and lithium metal, potentially paving the way for improved stability and performance in lithium-based battery systems.