Preventing Capacity Fading in Lithium–Sulfur Batteries Using Sulfur Confinement in Mesoporous Carbon and Fluorinated Solvent-Based Electrolytes

• Published in: Journal of physical chemistry. C Vol. 127; no. 31; pp. 15069 - 15077
• Main Authors: Torii, Yuya, Matsui, Yukiko, Yamamoto, Kentaro, Uchida, Satoshi, Yamazaki, Shigeaki, Watanabe, Toshiki, Nakanishi, Koji, Uchiyama, Tomoki, Uchimoto, Yoshiharu, Ishikawa, Masashi
• Format: Journal Article
• Language: English
• Published: American Chemical Society 10.08.2023
• Subjects: C: Energy Conversion and Storage
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.3c02992

The capacity of lithium–sulfur (Li–S) batteries fades continuously with the increasing number of charge–discharge cycles as a result of the dissolution of lithium polysulfides (Li2S x , x = 4–8) generated during charge and discharge into the electrolyte. To mitigate this, a fluorinated solvent-based electrolyte was applied to a mesoporous carbon cathode containing confined sulfur for use in a Li–S battery. During operation, a solid electrolyte interface (SEI) was formed at the surface of the positive electrode because of electrolyte decomposition, and the SEI significantly suppressed the dissolution of the lithium polysulfides. The chemical composition and formation mechanism of the SEI were determined through X-ray photoelectron spectroscopy and operando soft X-ray absorption spectroscopy analyses. Crucially, the Li–S battery assembled with the fluorinated electrolyte exhibited favorable discharge rate performance (620 mAh/g-of-sulfur at a 5C rate) and good cycling stability.