Advances in solid electrolytes (SEs) with superionic conductivity and stabilized electrode-electrolyte interfaces are key enablers for all-solid-state batteries (SSBs) to meet the energy density and cost targets for next-generation batteries for electric vehicles. Argyrodite sulfide-based electrolytes with the nominal composition Li₆PS₅X; where X= Cl and/or Br, I provide several key advantages over other types of SE counterparts, including (i) exceptionally high ionic conductivities up to 10^-2 S/cm at room temperature (comparable to nonaqueous liquid electrolytes), (ii) availability of low temperature and inexpensive synthesis routes to produce glass, glass-ceramic, and crystalline structures, and (iii) soft mechanical properties facilitating material processing and solid-state battery (SSB) fabrication. Several key challenges exist for the practical use of the argyrodite sulfide-based electrolyte in an SSB: (i) scale-up synthesis to produce phase-pure materials, (ii) rationale processing method development to produce free-standing thin film SSEs, and (iii) identifying buried interfacial side-reaction products at the electrode/electrolyte interfaces using advanced characterization tools. In this talk, we will present our recent achievements focusing on tackling each of these challenges, including (i) solution-based synthesis of Li₆PS₅X; (ii) optimizing binder, slurry composition, and processing method to make Li₆PS₅X thin film (<50 µm) SSEs, and (iii) combining in-situ Raman spectroscopy and microscopy with complementary electrochemical impedance spectroscopy (EIS) to explore electrode/ Li₆PS₅X interfacial stability. Acknowledgment This research conducted at Oak Ridge National Laboratory, managed by UT Battelle, LLC, for the U.S. Department of Energy (DOE) is sponsored by the Office of Energy Efficiency and Renewable Energy (EERE) in the Vehicle Technologies Office (VTO) through the Advanced Battery Materials Research (BMR) Program.