Coupling of Oxygen Vacancies and Heterostructure on Fe ₃O ₄ via an Anion Doping Strategy to Boost Catalytic Activity for Lithium‐Sulfur Batteries

Abstract

The sluggish reaction kinetics and severe shutting behaviors of sulfur cathodes are the major roadblocks to realizing the practical application of lithium−sulfur (Li−S) batteries and need to be solved through designing/constructing rational sulfur hosts. Herein, an effective alternative material of Fe ₃O _{4− x} /FeP in‐situ embedded in N‐doped carbon‐tube (Fe ₃O _{4− x} /FeP/NCT) is proposed. In this fabricated heterostructure, NCT skeleton works as a sulfur host provides physical barrier for lithium polysulfides (LiPSs), while Fe ₃O _{4− x} /FeP heterostructure with abundant oxygen vacancies provides double active centers to simultaneously accelerate e ⁻/Li ⁺ diffusion/transport kinetics and catalysis for LiPSs. Through the respective advantages, Fe ₃O _{4− x} /FeP/NCT exhibits synergy enhancement effect for restraining sulfur dissolution and enhancing its conversion kinetics. Furthermore, the promoted ion diffusion kinetics, enhanced electrical conductivity, and increased active sites of Fe ₃O _{4− x} /FeP/NCT are enabled by oxygen vacancies as well as the heterogeneous interfacial contact, which is clearly confirmed by experimental and first‐principles calculations. By virtue of these superiorities, the constructed cathode shows excellent long‐term cycling stability and a high‐rate capability up to 10 C. Specially, a high areal capacity of 7.2 mAh cm ⁻² is also achieved, holding great promise for utilization in advanced Li−S batteries in the future.