Weakening Li+ De-solvation Barrier for Cryogenic Li-S Pouch Cells.

Abstract

Li-S batteries hold promise for pushing cell-level energy densities beyond 300Wh 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 (5.6mg 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 350Wh kg-1 at 0°C, offering a promising route toward a practical high-energy cryogenic Li-S battery.