Weakening Li+ De‐solvation Barrier for Cryogenic Li–S Pouch Cells

• Published in: Advanced materials (Weinheim) 2023-03, Vol.35 (9), p.e2208590-n/a
• Main Authors: Ji, Haoqing, Wang, Zhenkang, Sun, Yawen, Zhou, Yang, Li, Sijie, Zhou, Jinqiu, Qian, Tao, Yan, Chenglin
• Format: Article
• Language: English
• Subjects: Density functional theory; de‐solvation barrier; Dilution; Electrolytes; Electrolytic cells; Lithium sulfur batteries; Li–S batteries; Low temperature; Materials science; Molecular dynamics; Room temperature; Solvation; solvation structure
• ISSN: 0935-9648; 1521-4095
• DOI: 10.1002/adma.202208590

Li–S batteries hold promise for pushing cell‐level energy densities beyond 300 Wh kg‐1 while operating at low temperatures (LTs, below 0 °C). However, the capacity release of existing Li–S batteries at LTs is still barely satisfactory, and there is almost no verification of the practicability of Li–S batteries at LTs in the Ah‐level pouch cell. Here, antecedent molecular dynamics (MDs) combined with density functional theory analysis are used to systematically investigate Li+ solvation structure in conventional Li–S batteries at LTs, which unprecedentedly reveals the positive correlation between lithium salt concentration and Li+ de‐solvation barrier, indicating dilute electrolytes can enhance the Li+ de‐solvation kinetics and thus improve the capacity performance of cryogenic Li–S batteries. These insights derived from theoretical simulations invested Li–S batteries with a 67.34% capacity retention at −40 °C compared to their room temperature performance. In particular, an Ah‐level Li–S pouch cell using dilute electrolytes with a high sulfur loading (5.6 mg cm‐2) and lean electrolyte condition is fabricated, which delivers a discharge capacity of about 1000 mAh g‐1 and ultra‐high energy density of 350 Wh kg‐1 at 0 °C, offering a promising route toward a practical high‐energy cryogenic Li–S battery. Antecedent theoretical simulations decipher the correlation between lithium salt concentration and Li+ desolvation barrier in the electrolyte, indicating dilute electrolytes can enhance kinetics of sulfur cathode effectively. This insight endows Li–S pouch cells with an ultra‐high energy density of 350 Wh kg‐1 at 0 °C, demonstrating great potential for cryogenic Li–S batteries.