CoSe QDs/Sn3O4 PCNFs with high catalytic conversion kinetics towards high-efficiency Li-S batteries.

Abstract

The redox reactions occurring at positive electrode of the lithium-sulfur (Li-S) batteries involve several key electrocatalytic processes that significantly impact the overall performance of the electrochemical energy storage system. This study presents a heterogeneous catalytic composite material composed of CoSe quantum dots (QDs) integrated with Sn₃O₄ nanosheets, which enhances the overall ionic conductivity and accessibility of active sites within the cathode. This controlled migration effectively traps polysulfides within the cathode, reducing their dissolution into the electrolyte and mitigating the shuttle effect. Li-S batteries incorporating CoSe QDs/Sn₃O₄ porous carbon nanofibers (PCNFs) demonstrate a high discharge capacity of 1596.9 mAh g^-1 at 0.1 C, along with remarkable cycling stability, achieving 1500 cycles at 2 C with a minimal capacity decay of 0.024 % per cycle. Even under a high sulfur loading conditions of 8.61  mg cm^-2 and a low electrolyte to sulfur ratio of approximately 4.6 μL mg^-1, the CoSe QDs/Sn₃O₄ PCNFs cathode delivers an initial discharge-specific capacity of 732.0 mAh g^-1 at 0.2 C. Through this method, we accomplished the size control and uniform distribution of CoSe QDs, and this method can be extended to the synthesis of other metal oxide and metal sulfide QDs, offering a novel idea for the application of QDs in polysulfide catalysis.