Biomimetic Molecule Catalystss To Promote The Conversion Of Polysulfides For Advanced Lithium-sulphur Batteries

Rechargeable lithium-sulfur（Li–S）batteries are considered one of the most promising candidates for next-generation battery technology due to their high theoretical energy density(2600 Wh kg^-1),low cost,and environmental friendliness.Despite its great advantages,the complex chemical reactions in Li-S batteries impede the practical application of Li-S batteries.In view of the slow reaction kinetics,it is urgent to introduce a mediator with high catalytic activity to solve the following problems:1)severe shuttle effect;2)slow polysulfide conversion process;3)undesired side reactions.In this paper,biomimetic molecular mediators are introduced into lithium-sulfur batteries as additives to accelerate the reaction kinetics of liquid polysulfide conversion and activate the initial solid-liquid two-phase transformation.The main content of the article is as follows:（1）The biomimetic molecule hemin was added to the functionalized multi-walled carbon nanotube-supported elemental sulfur composite as the positive electrode（CNTs-COOH@hemin）.After optimization,a very high initial capacity of 1637.8 m Ah g^-1was obtained at 0.2 C,and after 1800 cycles,the capacity reduction rate was only 0.042%.In addition,the structures of the three composites and their working mechanisms in Li–S batteries,especially for CNTs-COOH@hemin,were systematically investigated using in-situ vibrational spectroscopy,X-ray photoelectron spectroscopy（XPS）,in-situ ultraviolet（UV）–visible spectroscopy,and density functional theory（DFT）calculations,etc.（2）Histidine（His）is used as a regulatory molecule and heme molecule to prepare a hemin@His composite material,and is used in the cathode of lithium-sulfur batteries.At 0.2 C,the optimized CNTs-hemin@His cathode has a higher initial capacity of 1549.7m Ah g^-1,and after 800 cycles at a rate of 1 C,there is still no less than the reversible capacity of the unregulated molecular battery.