In operando Raman microscopy of the Cu/Li1.5Al0.5Ge1.5(PO4)3 solid electrolyte interphase

(LAGP) is a promising solid-state electrolyte (SSE) for solid-state batteries but suffers from side reactions with Li metal resulting in cracking and interfacial resistance rise which hinders its practical application. Herein, in operando Raman spectroscopy was performed to gain insights into local chemical and structural transformations of the Cu/LAGP interface during cathodic polarization.