Copper Zinc Sulfide (CuZnS) Quantum Dot-Decorated (NiCo)–S/Conductive Carbon Matrix as the Cathode for Li–S Batteries

Abstract

Sulfur composites consisting of electrochemical reactive catalysts/conductive materials are investigated for use in lithium–sulfur (Li–S) batteries (LSBs). In this paper, we report the synthesis, physicochemical and electrochemical properties of CuZnS quantum dots (CZSQDs) decorated with nickel–cobalt–sulfide ((NiCo)–S)) mixed with reduced graphene oxide (rGO)/oxidized carbon nanotube (oxdCNT) (rGO/oxdCNT) ((NiCo)–S@rGO/oxdCNT) composites. These composites are for the purpose of being the sulfur host cathode in Li–S batteries. The as-prepared composites showed a porous structure with the CZSQDs being uniformly found on the surface of the rGO/oxdCNT, which had a specific surface area of 26.54 m2/g. Electrochemical studies indicated that the (NiCo)–S@rGO/oxdCNT cells forming the cathode exhibited a maximum capacity of 1154.96 mAhg−1 with the initial discharge at 0.1 C. The smaller size of the CZSQDs (~10 nm) had a positive effect on the CZSQDs@(NiCo)–S@rGO/oxdCNT composites in that they had a higher initial discharge capacity of 1344.18 mAhg−1 at 0.1 C with the Coulombic efficiency being maintained at almost 97.62% during cycling. This latter property is approximately 1.16 times more compared to the absence of the Cu–Zn–S QD loading. This study shows that the CuZnS quantum dots decorated with a (NiCo)–S@rGO/oxdCNT supporting matrix-based sulfur cathode have the potential to improve the performance of future lithium–sulfur batteries.

Keywords

• lithium–sulfur batteries
• quantum dots
• conductive carbon materials
• metal sulfides
• sulfur host