Comparison of Sulfur Cathode Reactions between a Concentrated Liquid Electrolyte System and a Solid-State Electrolyte System by Soft X-Ray Absorption Spectroscopy,ACS Applied Energy Materials

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Comparison of Sulfur Cathode Reactions between a Concentrated Liquid Electrolyte System and a Solid-State Electrolyte System by Soft X-Ray Absorption Spectroscopy
ACS Applied Energy Materials ( IF 5.4 ) Pub Date : 2020-12-17 , DOI: 10.1021/acsaem.0c02063
Yao Xiao ₁ , Kentaro Yamamoto ₁ , Yukiko Matsui ₂ , Toshiki Watanabe ₁ , Atsushi Sakuda ₃ , Koji Nakanishi ₁ , Tomoki Uchiyama ₁ , Akitoshi Hayashi ₃ , Shoso Shingubara ₄ , Masahiro Tatsumisago ₃ , Masashi Ishikawa ₂ , Masayoshi Watanabe ₅ , Yoshiharu Uchimoto ₁

Affiliation

Sulfur is one of the promising next-generation cathode materials because of its low cost and high theoretical gravimetric capacity. However, the reaction mechanism of the sulfur cathode is largely influenced by the electrolyte and the intermediate sulfur species during the first discharge process has not been quantitatively explored in different electrolytes. In this study, we elucidated the reaction mechanism of sulfide cathodes by using three different electrolyte systems, viz., a conventional liquid electrolyte [LiPF₆/ethylene carbonate (EC)/ethylene-methyl carbonate (EMC)], a concentrated liquid electrolyte [lithium bis(trifluorosulfonyl)amide (LiTFSA)/tetraglyme (G4):1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (HFE)], and a solid-state electrolyte (Li₃PS₄). Soft X-ray absorption spectroscopy was used to examine the reaction mechanism of the sulfur cathode in the liquid and solid-state electrolytes during the first discharge process. In the conventional electrolyte, the sulfur cathode was reduced to long-chain polysulfide (S₆^2–) during the first discharge process, and the polysulfide subsequently dissolved into the electrolyte. In the concentrated electrolyte, the sulfur cathode was reduced to midchain polysulfide (S₄^2–) at the initial stage of the first discharge process and then reduced to short-chain polysulfide (S₂^2–) and Li₂S, followed by the formation of long-chain polysulfide (S₆^2–). In the solid-state electrolyte, the sulfur cathode was reduced to long-chain polysulfide (S₆^2–) at the initial stage of the first discharge process and was gradually reduced to mid-chain polysulfide (S₄^2–), short-chain polysulfide (S₂^2–), and Li₂S. The differences in these reaction pathways govern electrochemical properties such as the difference in discharge voltage.

中文翻译：

软X射线吸收光谱法比较浓缩液电解质体系和固态电解质体系中硫阴极反应

硫由于其低成本和高理论重量而成为有希望的下一代阴极材料之一。然而，硫阴极的反应机理在很大程度上受电解质的影响，并且在第一放电过程中的中间硫种类尚未在不同的电解质中进行定量研究。在这项研究中，我们通过使用三种不同的电解质系统阐明了硫化物阴极的反应机理。，常规液体电解质[LiPF ₆ /碳酸亚乙酯（EC）/乙烯-甲基碳酸酯（EMC）]，浓缩液体电解质[双（三氟磺酰基）酰胺锂（LiTFSA）/四甘醇二甲醚（G4）：1,1,2， 2-四氟乙基2,2,3,3-四氟丙基醚（HFE）]和固态电解质（Li ₃PS ₄）。使用软X射线吸收光谱法检查第一次放电过程中液态和固态电解质中硫阴极的反应机理。在传统的电解液中，在第一个放电过程中，硫阴极被还原为长链多硫化物（S ₆^2-），随后多硫化物溶解到电解液中。在浓电解质中，在第一个放电过程的初始阶段，硫阴极被还原为中链多硫化物（S ₄^2–），然后被还原为短链多硫化物（S ₂^2–）和Li ₂ S，随后被长链多硫化物的形成（S ₆^2–）。在固态电解质中，在第一个放电过程的初始阶段，硫阴极被还原为长链多硫化物（S ₆^2-），并逐渐被还原为中链多硫化物（S ₄^2-），短链多硫化物（S ₂^2-），和Li ₂在这些反应途径S.差异支配电化学特性如放电电压的差值。

更新日期：2021-01-25

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