Virtual Electrode plating XPS Investigation of the Solid Electrolyte Interphase formed between Li Metal Anode and LGPS and LAGP Solid Electrolytes

In situ X-ray photoelectron spectroscopy (XPS) techniques have proven to be powerful tools for the characterisation of the solid electrolyte interphase (SEI) formed between the anode and solid electrolyte (SE) in solid-state batteries. XPS offers access to time and operational condition-resolved information on the SEI’s chemical composition in the absence of destructive sample preparation. Here we present a Virtual Electrode Plating XPS (VEP-XPS) investigation of the composition and stability of the SEI formed between lithium metal and two different solid electrolytes: Li10GeP2S12 (LGPS)andLi1.5Al0.5Ge1.5(PO4)3 (LAGP). LAGP shows slower SEI formation kinetics, as proven by the emergence of a metallic lithium signal, while LGPS exhibits rapid SEI growth that prevents metallic lithium from plating. We attribute these observations to the SEI composition, distribution and physical properties of secondary de- composition products and in particular to the mixed ion-electron conductive Li3P which can be observed in LGPS and not in LAGP