All-solid-state lithium-ion batteries (ASSBs) represent a new generation of energy storage tools containing only solid components. They are of great interest to researchers and manufacturers thanks to their high energy density, which makes them promising candidates for electric transport applications. Among different types of solid-state electrolytes for lithium-ion batteries (LIBs), sulfide-based electrolytes (SSEs) have several advantages, such as high ionic conductivity and malleability [1, 2]. However, one of their main drawbacks is a high sensitivity towards air humidity [3]. Fast reaction of the SSEs with water results in the degradation of their structure and release of toxic gas (H2S) when exposed to even low concentrations of humidity. This factor leads to significant process cost and safety issues associated with mass production of ASSBs with sulfide-based SEs.The purpose of the present work is to study in details reactivity of SSEs towards humidity by following two main directions: The development of a flow-through setup that allows a better identification and highly precise quantification of gases (H2S or others) generated during reaction between water (humidity) and commercial SSEs: this flow-through setup intends to solve problems usually encountered when using closed-type setups, which are the most used setups in the literature[3, 4]. These problems include over-concentration of detected gases and low reproducibility of measurements;Physico-chemical and electrochemical characterizations of pristine and humidity exposed-SSEs in order to reveal the main factors affecting sensitivity towards humidity and to understand the degradation mechanisms. First, the efficiency of the flow-through gas analysis setup developed had been validated: H2S detection curves obtained for commercial SSE powders (Li6PS5Cl, Li6PS5Br, Li7P3S11, Li3PS4, Li10GeP2S12) in contact with humid Argon (30 to 200 ppm H2O in Ar) are highly reproducible (see example in Fig. 1 and Table 1). Measurements conducted at different humidity levels allowed accessing kinetics of water-induced degradation reactions involved. SSE powders characterizations using XRD, Raman, XPS, SEM, EIS, granulometry before and after exposure to humidity provided an insight into degradation-related phenomena taking place: morphology deterioration, loss of structure and conductive structural groups, drastic increase of ionic resistance. A relationship between the structure of SSE and its reactivity towards water was found and described.Refs[1] Energy Storage Mater. 2018, 14, 58–74 ; [2] Nano Energy 2021, 83, 105858 ; [3] Solid State Ion. 2011, 182 (1), 116–119 ; [4] Chem. Mater. 2020, 32 (6), 2664–2672. Figure 1