Efficient Co0.85Se-CNT sulfur cathode derived from strong catalyst-support interactions: Contribution of adsorption-catalysis mechanism to the redox kinetics of polysulfides

Abstract

The sluggish conversion chemistry and the notorious ‘shuttle effect’ of lithium polysulfides (LiPSs) are hindering the widespread application of lithium-sulfur batteries (LSBs). Herein, N-doped carbon nanotubes arrays anchored with highly dispersed Co0.85Se nanoparticles were in-situ grown on 3D carbon paper substrates (Co0.85Se-CNT@CP) to promote redox kinetic. The derived sulfur cathode (S/Co0.85Se-CNT@CP) exhibited a sufficient chemisorption ability to accelerate the conversion kinetics and showed considerable capability (1210 mAh/g at 0.2C) and impressive cyclic stability (516 mAh/g at 2.0C after 500cycles). Even at a high loading of 6.0 mg cm−2, the assembled batteries performed a high capacity of 500 mAh/g at 2.0C after 500cycles. The exceptional performance is attributed to the following reasons: On the one hand, the highly efficient conductive carbon nanotubes not only offer sufficient accommodation space for sulfur, but also provide physically confinement for polysulfides. On the other hand, the Co0.85Se nanoclusters drove the transformation of more elemental sulfur to Li2S2/Li2S. In addition, the S/Co0.85Se-CNT@CP did not require conventional binders, thus enhanced surface the reaction kinetic and electron transfer. The associated conversion mechanism was studied by ex-situ XPS, and an adsorption-catalytic model was established to elucidate the electrochemical mechanism. This study proposes a feasible strategy to solve the severe LiPSs shuttling and the sluggish conversion kinetics of LSBs.