The Formation of the Solid-/Liquid Electrolyte Interphase (SLEI) on NASICON-Type Glass Ceramics and LiPON

Most electrochemical energy storages (battery cells) consist of solid electrodes separated by a liquid electrolyte (LE). If electrode materials are – at least partially – soluble in the electrolyte, detrimental mass transport between both electrodes (electrode cross-talk) occurs. The shuttle mechanism in lithium-sulfur batteries or leaching of Mn in high voltage cathode materials are important examples. Implementing a solid electrolyte (SE) membrane between the electrodes is a comprehensible approach to suppress undesired mass transport but additional resistances arise due to charge transport across the SE and charge transfer through the solid/liquid electrolyte interfaces. The latter contribution is often overlooked as its determination is challenging, however, these interface properties are crucial for practical application. In previous work a resistive solid-/liquid-electrolyte interphase “SLEI” was found at the interface between the SE lithium aluminum germanium phosphate (LAGP) in contact with a liquid ether-based electrolyte. Here we aim for deeper insight into this interphase formation, referring to a lithium ion conducting glass ceramic (NASICON-type) and the commonly used thin film ion conductor “LiPON” (lithium phosphorous oxide nitride). The growth of the SLEI is monitored by a combination of electrochemical characterization, XPS (x-ray photoelectron spectroscopy) and time-of flight secondary ion mass spectrometry (ToF-SIMS).