A Low-Cost Liquid-Phase Method of Synthesizing High-Performance Li6PS5Cl Solid-Electrolyte

ABSTRACT: Li6PS5Cl is an extensively studied sulfide-solidelectrolyte for developing all-solid-state lithium batteries. However, its practical application is hindered by the high cost of its raw material lithium sulfide (Li2S), the difficulty in its massive production, and its substandard performance. Herein we report an economically viable and scalable method, denoted as de novo liquid phase method, which enables in synthesizing highperformance Li6PS5Cl without using commercial Li2S but instead in situ making Li2S from cheap materials of lithium chloride (LiCl) and sodium sulfide. LiCl, a raw material needed for making both Li2S and Li6PS5Cl, can be added at a full-scale in the beginning and unrequired to separate when making the intermediate Li3PS4. Such a consecutive feature makes this method time-efficient; and the excess amount of LiCl in the step of making Li2S also facilitates removing the byproduct of sodium chloride via the common ion effect. The materials cost of this method for Li6PS5Cl is similar to $55/kg, comparable with the practical need of $50/kg. Moreover, the obtained Li6PS5Cl shows high ionic conductivity and outstanding cyclability in full battery tests, that is, similar to 2 mS/cm and >99.8% retention for 400+ cycles at 1 C, respectively. Thus, this innovative method is expected to pave the way to develop practical sulfide-solid-electrolytes for all-solid-state lithium batteries.

Automated summary

A new de novo liquid phase method has been developed to synthesize high-performance Li6PS5Cl at a lower cost, overcoming the previous drawbacks of high material cost and low performance.