CoFe2O4@rGO as a Separator Coating for Advanced Lithium–Sulfur Batteries

Abstract

Lithium–sulfur (Li–S) batteries are hindered by the undesired shuttle effect and sluggish electrochemical conversion kinetics. Herein, a well‐designed CoFe2O4@reduced graphene oxide (CFO@rGO) composite is used to modify the separator to develop a multifunctional polysulfide barrier. Density functional theory (DFT) calculations confirm that highly electronegative oxygen ions in CFO tend to bond with transition metal (TM) ions at octahedral (Oh) sites, which induces the formation of FeS and CoS bonds between CFO and polysulfides. This indicates that CFO can effectively anchor polysulfides. Furthermore, the low Li2S decomposition energy barrier and Li+ diffusion energy barrier reveal that CFO can accelerate the redox reaction kinetics of sulfur species. Electronic structure calculations speculate that the low‐energy barrier can be attributed to the electron‐hopping phenomenon between TM ions of different valence states at Oh sites. Benefiting from these advantages, a CFO@rGO/PP separator demonstrates satisfactory cycling performance (0.087% capacity decay rate at 2C with 500 cycles) and superb rate performance (686 mAh g−1 at 5C). This work provides a valuable reference for future research on spinel‐type materials as electrocatalysts for Li–S batteries.