Expediting solid electrolyte synthesis: Microwave-assisted wet synthesis of halogen-rich Li-argyrodite

Abstract

Li-argyrodites are promising solid electrolytes (SEs) for solid-state Li-ion batteries (SSLBs), but their large-scale industrial application remains a challenge. Conventional synthesis methods for SEs suffer from long reaction times and high energy consumption. In this study, we present a wet process for the synthesis of halogen-rich argyrodite Li_6−aPS_5−aCl_1+a precursors (LPSCl_1+a-P, a = 0–0.7) via an energy-saving microwave-assisted process. Utilizing vibrational heating, we accelerate the formation of Li-argyrodite precursor, even at excessive Cl-ion concentration, which significantly shortens the reaction time compared to traditional methods. After crystallization, we successfully synthesize the Li-argyrodite, Li_5.5PS_4.5Cl_1.5, which exhibits the superior ionic conductivity (7.8 mS cm⁻¹) and low activation energy (0.23 eV) along with extremely low electric conductivity. The Li_5.5PS_4.5Cl_1.5 exhibits superior Li compatibility owing to its high reversible striping/plating ability (over 5000 h) and high current density acceptability (1.3 mA cm⁻²). It also exhibits excellent cycle reversibility and rate capability with NCM622 cathode (148.3 mA h g⁻¹ at 1 C for 100 cycles with capacity retention of 85.6%). This finding suggests a potentially simpler and more scalable synthetic route to produce high-performance SEs.