Biomimetic Molecule Catalysts to Promote the Conversion of Polysulfides for Advanced Lithium–Sulfur Batteries

To overcome the shuttle effect in Li–S batteries, novel biomimetic molecule catalysts are synthesized by grafting hemin molecules to three functionalized carbon nanotube systems (CNTs–COOH, CNTs–OH, and CNTs–NH 2 ). The Li–S battery using the CNTs–COOH@hemin cathode exhibits the optimal initial specific capacity (1637.8 mAh g −1 ) and cycle durability (up to 1800 cycles). Various in situ characterization techniques, such as Raman spectroscopy, Fourier-transform infrared reflection absorption spectroscopy, and UV–vis spectroscopy, combined with density functional theory computations are used to investigate the structure–reactivity correlation and the working mechanism in the Li–S system. It is demonstrated that the unique structure of the CNTs-COOH@hemin composite with good conductivity and adequate active sites resulting from molecule catalyst as well as the strong absorption to polysulfides entrapped by the coordinated Fe(III) complex with Fe  O bond enables the homogeneous dispersion of S, facilitates the catalysis and conversion of polysulfides, and improves the battery's performance.