Determination of Reaction Enthalpies of Synthesizing β-Li₃PS₄ in Tetrahydrofuran

While some promising materials for all-solid-state batteries are already extensively investigated in a lab scale, the transferability to mass production is still a limiting factor. β-lithium thiophosphate (β-Li₃PS₄) has good ionic conductivity and can be synthesized wet-chemically, which opens up the possibility for scale-up. For safe upscaling, the enthalpies of the synthesis steps need to be examined in order to handle exothermic and endothermic processes. Here, the reaction enthalpies of the wet-chemical synthesis of β-Li₃PS₄ in tetrahydrofuran (THF) are determined. The synthesis routine is established in a lab scale, and the synthesis success is confirmed via X-ray diffraction (XRD) and electrochemical impedance spectroscopy (EIS). The reaction of the educts in THF is investigated using a reaction calorimeter and shows a strongly exothermic process. The subsequent processes are examined using differential scanning calorimetry with thermogravimetric analysis and show a strong endothermic process during solvent removal and a slightly exothermic process during crystallization.