Abstract
We present a potentially eco-friendly, cost-efficient strategy for synthesizing high-purity Li(2)S, a key precursor for sulfide-based solid electrolytes. While these electrolytes surpass conventional organic counterparts in both safety and performance, their widespread application is hindered by the high cost of Li(2)S. Here, a solvent-free metathesis route is developed, in which thiourea serves as an S(2)⁻ donor to sulfurize LiOH, enabling scalable Li(2)S production (∼100 g per batch) with significantly reduced projected costs. During the process, intermediates (H(2)NCN, H(2)O) are transformed into benign gases (CO(2), NH(3)) that spontaneously leave the system, thereby driving Li(2)S formation without ΔG(mix) limitations. The as-synthesized Li(2)S is successfully applied to prepare sulfide-based solid electrolytes such as Li(10)GeP(2)S(12) and argyrodite-Li(5.5)PS(4.5)Cl(1.5), achieving laboratory-scale (1 kg) production costs reduction of up to 27.5% and 92.9%, respectively. Furthermore, all-solid-state batteries employing Li(5.5)PS(4.5)Cl(1.5) demonstrate electrochemical performance comparable to those fabricate with commercial Li(2)S. This scalable methodology thus may provide a proming pathway to bridge low-cost Li(2)S synthesis with the practical deployment of sulfide-based solid electrolytes, which may accelerate the commercialization of high-performance all-solid-state batteries.