Efficient Co_0.85Se-CNT sulfur cathode derived from strong catalyst-support interactions: Contribution of adsorption-catalysis mechanism to the redox kinetics of polysulfides

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 Co_0.85Se nanoparticles were in-situ grown on 3D carbon paper substrates (Co_0.85Se-CNT@CP) to promote redox kinetic. The derived sulfur cathode (S/Co_0.85Se-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 Co_0.85Se nanoclusters drove the transformation of more elemental sulfur to Li₂S₂/Li₂S. In addition, the S/Co_0.85Se-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.