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

Abstract

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 Mo2S3/MoS2@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 Mo2S3 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 MoS2@CNFs@PP separator achieved an areal capacity of 5.8 mAh cm−2 at high sulfur loading (∼4.5 mgs 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.