Synthesis of high-purity Li2S nanocrystals via metathesis for solid-state electrolyte applications. Issue 14 (22nd March 2023)

• Record Type: Journal Article
• Authors: Smith, William H.; Vaselabadi, Saeed Ahmadi; Wolden, Colin A.
• Is Part Of: Journal of materials chemistry. Volume 11:Issue 14(2023)
• Page Start: 7652
• Page End: 7661
• Publication Date: 2023-03-22
• Subjects: Materials -- Research -- Periodicals; Chemistry, Analytic -- Periodicals; Environmental sciences -- Research -- Periodicals; 543.0284
• DOI: 10.1039/d3ta00076a
• Languages: English
• ISSNs: 2050-7488

Abstract

Abstract : Li2 S is the key precursor for synthesizing thio-LISICON electrolytes employed in solid state batteries. Abstract : Li2 S is the key precursor for synthesizing thio-LISICON electrolytes employed in solid state batteries. However, conventional synthesis techniques such as carbothermal reduction of Li2 SO4 aren't suitable for the generation of low-cost, high-purity Li2 S. Metathesis, in which LiCl is reacted with Na2 S in ethanol, is a scalable synthesis method conducted at ambient conditions. The NaCl byproduct is separated from the resulting Li2 S solution, and the solvent is removed by evaporation and thermal annealing. However, the annealing process reveals the presence of oxygenated impurities in metathesis Li2 S that are not usually observed when recovering Li2 S from ethanol. In this work we investigate the underlying mechanism of impurity formation, finding that they likely derive from the decomposition of alkoxide species that originate from the alcoholysis of the Na2 S reagent. With this mechanism in mind, several strategies to improve Li2 S purity are explored. In particular, drying the metathesis Li2 S under H2 S at low temperature was most effective, resulting in high-purity Li2 S while retaining a beneficial nanocrystal morphology (∼10 nm). Argyrodite electrolytes synthesized from this material exhibited essentially identical phase purity, ionic conductivity (3.1 mS cm −1 ), activation energy (0.19 eV), and electronic conductivity (6.4 × 10 −6 mS cm −1 ) as that synthesized from commercially available battery-grade Li2 S.