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.