A solid electrolyte with a small particle size, good mechanical properties and high ionic conductivity is required to achieve high energy and power density in the all-solid-state battery. Here, we report an instantaneous preparation of high lithium-ion conducting sulfide solid electrolyte Li7P3S11 by a simple procedure involving a liquid phase process under ultrasonic irradiation and low thermal treatment at 220 degrees C. A short reaction time of 30 min was enough to produce the formation of PS43- units. Subsequent drying and heating processes led to the precipitation of the Li7P3S11 phase with a particle size below 500 nm, achieving high ionic conductivity of 1.0 x 10(-3) S cm(-1) at 22 degrees C and a low activation energy of 12.8 kJ mol(-1)

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Preparation of sulfide-based Li-ion conductive solid electrolytes by a liquid-phase process has been proposed as an effective route for industrial scaling-up. However, reaction mechanisms in the liquid-phase synthesis or the role of solvents in the reactions are not yet well understood. Here, the reaction between Li2S and P2S5 in the composition of 50:50 mol% mediated by a polar aprotic solvent (acetonitrile) was investigated. The study of the crystal and local structure of the 50Li2S:50P2S5 sample revealed large chemical changes upon crystallization, highlighting the initial formation of a polymer-like (PS3 − )n intermediate. In the base of the (PS3 − )n intermediate, the reaction pathways for the formation of the P2S6 2− , PS4 3− , and P2S7 4− anions are elucidated. These findings give a deeper insight into the reaction mechanisms governing the liquid-phase synthesis of sulfide solid electrolytes and provide more specific criteria by which to design novel materials with superior characteristics through this liquid-phase approach.

Structure and ionic conductivity of sulfide solid electrolytes in the Li2S–P2S5 system obtained by a liquid phase process.