A synergistic effect on a ternary Co-S-Se catalytic material for simultaneous enhancement of the kinetics and stability in a lithium-sulfur battery

Abstract

In Li-S batteries (LSBs), the dissolution of lithium polysulfides (LiPSs) in an electrolyte and sluggish kinetics for the phase transition of LiPS lead to loss of S with the shuttle effect. As the use of catalysts offers one way to accelerate kinetics, various catalytic materials have been studied to overcome this crucial issue for LSBs. Among them, CoS2 is an attractive catalyst due to its good adsorption capability for LiPS and low oxidation energy barrier, but its slow kinetics requires a large amount of CoS2 (>30.0 wt%). Additionally, CoSe2 also has a high intrinsic conductivity, leading to acceleration of the redox kinetics for LiPS, but it has a weak attraction for LiPS. In this study, we introduce ternary CoSSe catalytic material to enhance the kinetics and stability even at low catalyst content (12.5 wt%) in LSBs. The CoSSe reveals a synergistic effect on the adsorption capability of CoS2 and the redox kinetics of CoSe2. As a result, compared with bare PP, KB/CoSSe-coated PP exhibits a 6 times higher rate performance (690.1 mAh/g at 1.0C) and 2 times higher cyclic stability (capacity retention of 84.3 % after 100 cycles at 0.5C) in a Li-S battery.