A novel pathway for sustained sulfides conversion via electrocatalyst-modified separator in lithium-sulfur batteries.

Electrocatalysts for boosting the conversion reactions of sulfur (S) have attracted increasing interest in achieving high S utilization and reaction kinetics in lithium-sulfur (Li-S) batteries. However, electrocatalysts may undergo complex changes in electrochemical conditions, especially for the liquid-solid conversion reactions, leading to an unsustainable electrocatalytic effect. Here, we present a functional separator modified with flower-like molybdenum sulfides grown on carbon nanofibers and reveal its real functional state and catalytic mechanism. The in-situ generated Mo 2 S 3 /MoS 2 @CNFs composite on the separator can enhance electron transfer between sulfur species and molybdenum sulfides, improving sulfur reduction kinetics. In addition, the highly electrochemical reactive Mo 2 S 3 located on the separator effectively avoids being covered by insulating sulfides, and provides a new reduction pathway for dissolved polysulfides, which significantly improve sulfur utilization and catalyst durability. As a result, the Li-S battery using MoS 2 @CNFs@PP separator achieved an areal capacity of 5.8 mAh cm⁻² at high sulfur loading (∼4.5 mg s cm⁻²) and demonstrated stable long cycling performance at 1 C. This work provides valuable guidance for maintaining catalyst activity in lithium-sulfur batteries via in situ reconstruction of electrocatalysts. [Display omitted] • The MoS 2 @CNFs@PP separator enables a new S reduction pathway with fast kinetics and maintains good catalytic durability. • Reveal the interaction between MoS 2 @CNFs and sulfides, as well as the regeneration of the electrocatalyst during the cycle. • The Li-S battery with MoS 2 @CNFs@PP exhibits 5.8 mAh cm⁻² areal capacity under high S loading and lean electrolyte condition. [ABSTRACT FROM AUTHOR]