The stability and lifetime of lithium-ion batteries hinges on deciphering the reactive processes that occur where the cathode meets the electrolyte. During cycling, electrolyte components oxidise at the cathode-electrolyte interface and form a thin, reactive interphase. This layer is commonly known as the solid electrolyte interphase (SEI), or more specifically as the cathode-electrolyte interphase (CEI) when formed on cathodes. Although the SEI is crucial for stabilising the cathode-electrolyte interface, it is only a few nanometres thick and chemically varied, which complicates its analysis with conventional analytical techniques like X-ray Photoelectron Spectroscopy (XPS) or Raman spectroscopy. Read more
