Building MoSe2-Mo2C incorporated hollow fluorinated carbon fibers for Li-S batteries

Abstract

Lithium-sulfur (Li-S) batteries are severely confined by the sluggish redox kinetics and serious shuttle effect, and these disadvantages cause rapid capacity decay and low sulfur utilization efficiency. We fabricate the polar MoSe2, Mo2C coupled with F-doped carbon fibers (FC), named as MoSe2@FC@Mo2C to serve as the step multi-electrocatalysts to selectively catalyze the short chain soluble lithium polysulfides (LiPSs) conversion (Li2S4 ↔ Li2S) via the polar FC and the long chain LiPSs conversion (S8 ↔ Li2S4) via MoSe2 and Mo2C. The MoSe2@FC@Mo2C/S cathode material delivered a high specific capacity of 1359 mAh g−1 (81% of its theoretical capacity) at 0.2C and excellent cycle performance when evaluated for Li-S batteries. A high reversible capacity of 802 mAh g−1 at 5C even with a lean E/S of 5 mLg−1, and a high sulfur loading of 5.5 mg cm−2 was delivered, a favorable cycle behavior at 2C over 1000 cycles (0.029% decay per cycle) was obtained, corroborating the effective LiPSs shuttling relief and high LiPSs conversion efficacy. This work propels the further practical application of Li-S batteries, especially those which are tethered by sluggish kinetics and inferior rate performance.