Iron-Induced Bidirectional Catalytic Effects for Sulfur Redox Reactions in Lithium–Sulfur Batteries
Electrocatalysts in lithium–sulfur (Li–S) batteries accelerate sulfur species redox reactions and restrict polysulfide shuttling, yet ideal electrocatalysts with remarkable bidirectional catalytic effects remain scarce. This work utilizes iron (Fe) to trigger bidirectional catalytic effects in a cobalt (Co) electrocatalyst, generating a metal alloy-based heterostructure of Co-Co7Fe3 dispersed homogeneously on carbon sheets (Co-Co7Fe3/CS). Electrochemical tests and in situ X-ray diffraction disclose significantly enhanced bilateral catalytic activity of Co-Co7Fe3 compared to bare Co, confirmed by self-discharge measurements. Post-cycling investigation validates protection of the Li metal anode from sulfur species corrosion. The Co-Co7Fe3/CS-modified coin cells deliver an exceptional rate capability of 603 mAh g–1 at 5.0 C and steady long-life cycling for 500 cycles at 1.0 and 2.0 C. Under high sulfur loadings and lean electrolyte conditions, an impressive areal capacity with stable cycling is realized. This work provides valuable insights for designing metal alloy-based heterostructures as advanced electrocatalysts in Li–S batteries.