Evaluation of various solvents for the wet-chemical synthesis of β-Li3PS4 under energy and environmental aspects

The transition from conventional lithium-ion batteries to all-solid-state batteries (ASSBs) offers the potential for higher energy and power densities. One promising material for solid-state electrolytes is crystalline β-Li3PS4, which can be synthesized using a wet-chemical route. The choice of solvent in this synthesis process plays a crucial role in terms of safety, energy efficiency, economic, and environmental impact. In this study, we conducted a preselection by evaluating various solvents for the synthesis of β-Li3PS4, considering their thermal properties, cost, hazard potential, and embodied environmental impact. Ethyl acetate (EA) emerged as the best alternative to tetrahydrofuran (THF) mostly due to its lower temperature increase during the mixing step and lower hazard potential. The synthesis using EA yields comparable product quality, which was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrochemical impedance spectroscopy (EIS) and showed favorable reaction enthalpies compared to THF. Choosing EA over THF also resulted in a 30% reduction in global warming potential (GWP). The findings emphasize the importance of solvent selection in the wet-chemical synthesis of β-Li3PS4, considering multiple aspects of process design.