Documenting the Synthesis Chemistry of Sulfide-Based Argyrodite Solid-State Electrolytes

Abstract As the core component of sulfide solid-state batteries, the solid-state synthesis of the sulfide-based argyrodite Li6PS5Cl (LPSC) solid electrolyte involves complex chemical reactions and intermediate phases, which remain rarely documented. Herein, we employ X-ray diffraction, Raman spectroscopy, and solid-state NMR to monitor the phase evolution during sintering. Owing to the high volatility of P2S5, stoichiometric imbalance occurs during heating, leading to impurities. By conducting the reaction in a sealed container with a suitable excess of P2S5, phase-pure LPSC is obtained, which exhibits an ionic conductivity of 3.2 mS cm–1. Moreover, standardized procedures for ionic conductivity measurements and all-solid-state battery testing are established. The LPSC-based battery with an NCM613 cathode and Li–In anode delivers a capacity retention of 96.6% after 260 cycles at 0.1C. This work clarifies the synthesis chemistry of argyrodite electrolytes and offers a scalable route to high-performance sulfide solid electrolytes.