Rational Electrolyte Solvent Screening for Practical Lithium–Sulfur Batteries

Practical lithium–sulfur (Li–S) batteries demand rapid sulfur redox kinetics and high Li-metal compatibility simultaneously, which cannot achieve this objective using current electrolyte based on 1,2-dimethoxyethane and 1,3-dioxolane. Herein, we propose a solvent screening criterion using the dielectric constant (ε r ) and donor number (DN) as a synergistic descriptor. Guided by this ε r –DN screening criterion, 75 solvents were classified as strong, midstrong, middle, weak, and nonsolvation solvents, respectively. The combination of midstrong/weak solvation solvents endows a distinctly gradient lithium polysulfides (LiPSs) solvation structure, suppressing their shuttle effect and enhancing Li-metal compatibility. This bestows the Li–S coin cell with an extremely high areal capacity of 9.4 mAh cm –2 under a high S mass loading (8.6 mg cm –2 ) and a low E/S ratio (3.6 μL mg –1 ). As a proof-of-concept, a 3 Ah-level pouch cell delivers a high energy density of 369 Wh kg –1 .