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Abstract The solid electrolyte interphase (SEI) is a dynamic, electronically insulating film that forms on the negative electrode of Li⁺batteries (LIBs) and enables ion movement to/from the interface while preventing electrolyte breakdown. However, there is limited comparative understanding of LIB SEIs with respect to those formed on Na⁺and K⁺electrolytes for emerging battery concepts. We used scanning electrochemical microscopy (SECM) for the in situ interfacial analysis of incipient SEIs in Li⁺, K⁺and Na⁺electrolytes formed on multi‐layer graphene. Feedback images using 300 nm SECM probes and ion‐sensitive measurements indicated a superior passivation and highest cation flux for a Li⁺‐SEI in contrast to Na⁺and K⁺‐SEIs. Ex situ X‐ray photoelectron spectroscopy indicated significant fluoride formation for only Li⁺and Na⁺‐SEIs, enabling correlation to in situ SECM measurements. While SEI chemistry remains complex, these electroanalytical methods reveal links between chemical variables and the interfacial properties of materials for energy storage.