Efficient immobilization and bidirectional catalysis of polysulfide conversion by FeCoP quantum dots for lithium-sulfur batteries

Using polysulfide electrocatalysts has become an effective strategy to improve the durability of lithium-sulfur batteries (LSBs) by regulating the precipitation and dissolution of lithium sulfide in the electrolyte. In this study, an FeCoP quantum dot (FeCoP-QD)-decorated nitrogen-doped carbon nanosheet (FeCoP-NCS) composite was prepared as a sulfur host for LSBs. In comparison with the other sulfur hosts reported in the literature, the optimal FeCoP-NCS sulfur host exhibited a fantastic bidirectional catalytic effect by greatly accelerating sulfur reduction during discharge and Li₂S oxidation during charging. The NCS substrate matrix with large specific surface area and high porosity provided the necessary channels for electron and ion transport. The assembled LSBs with the S@FeCoP-NCS cathode displayed a high capacity of 406 mA h g⁻¹ at 5C current density. Meanwhile, an excellent cycling performance with a capacity decay rate of 0.07% per cycle was observed for 500 cycles at 1C. This work demonstrated the potential of the FeCoP-NCS composite to be employed as an LSB electrode material with high-rate performance and long-term cycle stability.