Facile Synthesis of Li Argyrodite Materials as a Solid Electrolyte

Recently, research on next-generation secondary batteries has been actively pursued to develop high-energy-density and safe battery technologies. Currently, liquid electrolytes are utilized in Li-ion batteries (LIBs), which are flammable and volatile. Replacing the liquid electrolyte with solid materials could facilitate a high-capacity Li metal anode and enhance the safety of LIBs. Solid electrolyte materials in all-solid-state batteries (ASSBs) are categorized into oxides, sulfides, and polymers. Among these, sulfide-based materials offer several advantages, including high ionic conductivity and excellent processability.
The Li-argyrodite materials (Li₆PS₅X, X= Cl, Br, and I) are exemplary sulfide-based materials renowned for their high ionic conductivity and electrochemical stability. However, a challenge exists in the current synthesis of argyrodite due to the elevated cost of lithium sulfide (Li₂S), an essential precursor for producing argyrodite-type materials. The high expense associated with Li₂S amplifies the production costs of solid electrolytes, presenting a significant barrier that impedes the widespread commercialization of ASSBs. Consequently, there is a growing demand for an economical method to synthesize Li₂S at a lower cost. Another approach involves synthesizing sulfide-based materials without the reliance on Li₂S.
In this study, we introduce a novel method for synthesizing argyrodite materials, employing Li₃N as the primary starting material instead of Li₂S. Li₆PS₅Cl can be efficiently prepared through a one-step ball milling process. The resulting material (Li₆PS₅Cl) demonstrated an ionic conductivity of 1.1 mS cm^–1, comparable to the room temperature conductivity of established Li₆PS₅Cl solid electrolytes. This approach has the potential to lower the cost of solid electrolyte synthesis and enhance time efficiency.