Precise Synthesis of Fe-N2 Sites with High Activity and Stability for Long-Life Lithium–Sulfur Batteries

Precisely tuning the coordination environment of the metal center and further maximizing the activity of transition metal–nitrogen carbon (M-NC) catalysts for high-performance lithium–sulfur batteries are greatly desired. Herein, we construct an Fe-NC material with uniform and stable Fe-N2 coordination structure. The theoretical and experimental results indicate that the unsaturated Fe-N2 center can act as a multifunctional site for anchoring lithium polysulfides (LiPSs), accelerating the redox conversion of LiPSs and reducing the reaction energy barrier of Li2S decomposition. Consequently, the batteries based on a porous carbon nitride supported Fe-N2 site (Fe-N2/CN) host exhibit excellent cycling performance with a capacity decay of 0.011% per cycle at 2 C after 2000 cycles. This work deepens the understanding of the relationship between electronic structure of M-NC sites and the catalysis effect for the conversion of LiPSs. This strategy also provides a potent guidance for the further application of M-NC materials in advanced lithium–sulfur batteries.