Synthesis of high-purity Li 2 S nanocrystals via metathesis for solid-state electrolyte applications
Synthesis of high-purity Li 2 S nanocrystals via metathesis for solid-state electrolyte applications
复制标题
通过复分解合成高纯度Li 2 S纳米晶体用于固态电解质应用
DOI：
10.1039/d3ta00076a
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发表时间：
2023
影响因子：
11.9
通讯作者：
Wolden, Colin A.
中科院分区：
文献类型：
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作者：
Smith, William H.;Vaselabadi, Saeed Ahmadi;Wolden, Colin A.
Li2S 是合成固态电池中使用的硫代-LISICON 电解质的关键前体。然而，传统的合成技术（例如 Li2SO4 的碳热还原）并不适合生产低成本、高纯度的 Li2S。复分解是一种在环境条件下进行的可扩展合成方法，其中 LiCl 与 Na2S 在乙醇中反应。从生成的 Li2S 溶液中分离出 NaCl 副产物，并通过蒸发和热退火除去溶剂。然而，退火过程揭示了复分解 Li2S 中存在含氧杂质，而从乙醇中回收 Li2S 时通常不会观察到这些杂质。在这项工作中，我们研究了杂质形成的潜在机制，发现它们可能源自 Na2S 试剂醇解产生的醇盐物质的分解。考虑到这一机制，我们探索了几种提高 Li2S 纯度的策略。特别是，在低温下在 H2S 下干燥复分解 Li2S 是最有效的，可以获得高纯度的 Li2S，同时保留有益的纳米晶体形态（~10 nm）。由该材料合成的银汞矿电解质与由市售电池级Li2S合成的电解质表现出基本相同的相纯度、离子电导率（3.1 mS cm−1）、活化能（0.19 eV）和电子电导率（6.4 × 10−6 mS cm−1）。
Li2S is the key precursor for synthesizing thio-LISICON electrolytes employed in solid state batteries. However, conventional synthesis techniques such as carbothermal reduction of Li2SO4 aren't suitable for the generation of low-cost, high-purity Li2S. Metathesis, in which LiCl is reacted with Na2S in ethanol, is a scalable synthesis method conducted at ambient conditions. The NaCl byproduct is separated from the resulting Li2S solution, and the solvent is removed by evaporation and thermal annealing. However, the annealing process reveals the presence of oxygenated impurities in metathesis Li2S that are not usually observed when recovering Li2S 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 Na2S reagent. With this mechanism in mind, several strategies to improve Li2S purity are explored. In particular, drying the metathesis Li2S under H2S at low temperature was most effective, resulting in high-purity Li2S 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 Li2S.