Mechanical vs. chemical stability of sulphide-based solid-statebatteries. Which one is the biggest challenge to tackle? Overview of solid-state batteries and hybrid solid state batteries. Léa Rose Mangani, a Claire Villevieille * a,b Solid state batteries using sulphide-based solid electrolyte materials are believed to be the ideal solution for the next generation electrochemical energy storage. A deeper investigation of those systems revealed several challenges to be tackled or at least buffered to hope for a future commercialisation. Among them, we reported the interfacial one and the mechanical one. For the former, several solutions were proposed and adapted from the knowledge acquired in the Li-ion technology. For the latter, it was only sporadicaly studied but it reveals a real challenge for solid state batteries since mechanical know-how (implying wettability process on solid) was not really acquired in conventionnal Li-ion batteries and thus solutions from scratch need to be developed. Based on the aforementionned issues, it seems logical to develop hybrid solid state batteries (combining polymer electrolyte and solid state electrolyte) to ensure a future development of solid state technology.