Robust Electrocatalytic Li2 S Redox of Li-S Batteries Facilitated by Rationally Fabricated Dual-Defects.

Abstract

The commercialization of lithium-sulfur batteries with ultra-high theoretical energy density is restricted mainly by the notorious polysulfides "shuttle effect" and slow Li2 S redox reaction kinetics. A sulfur host material with high catalytic activity and high conductivity is greatly desired to improve its electrochemical performance. Herein, a sulfur host material, etched cotton@petroleum asphalt carbon (eCPAC), with high specific surface area and excellent catalytic activity, is demonstrated based on a synergistic strategy of introducing intrinsic lattice defects and composite carbon structure. Benefiting from in situ coupling of amorphous and crystalline materials, eCPAC exhibits high conductivity and high sulfur adsorbability. Furthermore, eCPAC containing dual intrinsic defect sites can catalyze the bidirectional sulfur chemistry of Li2 S and capture polysulfides, which is also demonstrated by systematic density functional theory calculations and the potential intermittent titration technique. S@eCPAC/Li cells exhibit excellent cycling stability and rate performance, with an average capacity decay rate of only 0.05% over 1000 cycles at 0.5 C and even 0.03% over 600 cycles at 5 C. Meanwhile, the practicality of eCPAC is proven in high-load batteries and pouch batteries. eCPAC provides a reliable strategy for achieving a win-win situation of capturing polysulfides and accelerating Li2 S redox kinetics.