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Sulfide‐based solid electrolytes (SEs) are amongst the most promising solid electrolytes for the development of solid‐state batteries (SSBs) due to their high ionic conductivity and processing advantage over oxide‐based SEs. However, one of the main drawbacks of sulfide SEs is their rapid degradation in presence of humidity. In this study, we investigated the effect of exposing three different sulfide SEs (Li7P3S11, the argyrodite Li6PS5Cl and the chloride‐doped argyrodite Li6‐xPS5‐xCl1+x) to the atmosphere of a dry room at a dew point (DP)=−40 °C. For the first time to the best of our knowledge, enhanced infra‐red (IR) laser technology was employed to follow and quantify online and in‐situ H2S evolution by the SEs in a dry room environment over 16 h. It was found that argyrodite compounds evolved approximately 8 times less H2S compared to Li7P3S11 over 16 h of exposure with peak concentrations between 5 and 16 ppm vol. The exposed materials were studied using X‐ray diffraction, Raman spectroscopy, electrochemical impedance spectroscopy, X‐ray photoelectron spectrometry (XPS) and galvanostatic cycling. XPS results revealed a formation of Li2CO3 on the surface of argyrodite SEs, which served as a robust passivation layer limiting considerably reactions with the dry room atmosphere. [ABSTRACT FROM AUTHOR]

Studies of argyrodite Li 6 PS 5 Cl as solid electrolyte are increasing, motivated by its high ionic conductivity and its easy processability. However, development of All-Solid-State-Batteries lies on the ability to produce such compound with a good purity. This work presents the characterization results of different argyrodite grades: commercial and homemade one. In parallel, synthesis of Li 6 PS 5 Cl from Li 4 P 2 S 7 precursor is reported for the first time. The purity effect on these properties will be explored by using X-ray diffraction coupled with Raman spectroscopy and electrochemical impedance spectroscopy techniques. Crystal properties investigations will be particularly conducted, given that smaller crystallite sizes would lead to an enhanced ionic percolation network by increasing the microstructure homogeneity in catholyte. Such SE could be obtained only by avoiding a post synthesis annealing treatment. Finally, electrochemical properties of the different reported grades will also be discussed in this study. We demonstrate here 1. the beneficial effect of Li 4 P 2 S 7 to obtain a pure sulfur-based solid electrolyte with nanometric crystallites without solid state synthesis and 2. the impact of impurities on its ionics and electrochemical properties. [Display omitted] • Characterization of commercial and homemade Li 6 PS 5 Cl grades by XRD, Raman and EIS. • New route synthesis of Li 6 PS 5 Cl through amorphous phase based on Li 4 P 2 S 7 compound. • Preparation of nanometric crystallites of Li 6 PS 5 Cl with enhanced ionic conductivity. • Influence of impurities on electrochemical properties. [ABSTRACT FROM AUTHOR]