Rational design of one-pot solvent-assisted synthesis for multi-functional Sn-substituted superionic Li argyrodite solid electrolytes

Sulfide-based Li superionic conductors are being considered good solid electrolytes for all-solid-state batteries. Despite some benefits of conventional solid-state methods, the end goal of the synthesis of sulfide electrolytes is the development of new liquid-phase methods. Herein, we demonstrate the rational design of a one-pot solvent-assisted route for the simple, facile, and low-cost synthesis of the Sn-substituted Li argyrodite superionic conductors. Our method enables the successful incorporation of Sn into the host lattices, yielding highly crystalline materials with high ionic conductivity (∼2 mS cm⁻¹), good air stability (20% humidity), and excellent Li metal compatibility (1500 h stability). Benefitting from these, at 0.1C, the full cell based on Li_6.125P_0.875Sn_0.125S₅Br exhibits an initial discharge capacity of 151 mA h g⁻¹ and ∼66% capacity retention after 50 cycles (99 mA h g⁻¹). This work presents an unprecedented solvent-engineered approach for the fabrication of versatile Li argyrodites substituted with aliovalent cations.