Reducing polysulfide hydrodynamic radius toward low-temperature lithium–sulfur batteries

Lithium–sulfur (Li–S) batteries are promising in realizing high energy density. Employing weakly solvating electrolytes (WSEs) further improves the anode stability. However, the lithium polysulfide (LiPS) redox kinetics is hindered in WSEs, and the underlying mechanism remains unclear. Herein, the LiPS kinetics in WSEs is quantitatively deciphered using rotating disk electrode analysis. The electron transfer number during oxidation is reduced in WSEs, evidencing intrinsically suppressed oxidation extent. Meanwhile, the diffusion coefficient and the electrolyte viscosity concurrently increase, implying a reduced LiPS hydrodynamic radius in WSEs based on the Stokes–Einstein relation and corresponding to inhibited LiPS molecular aggregation. Attributed to the reduced aggregation, WSE-based Li–S batteries exhibit record-low-temperature performances, delivering 8.0 mAh cm⁻² and 303 Wh kg⁻¹ at 0°C in 6 Ah-level pouch cells. This work establishes a new kinetic analysis methodology to guide rational electrolyte design and highlights the promise of WSEs to enable low-temperature Li–S batteries.