Lithium–sulfur batteries possess high theoretical energy density but suffer from rapid capacity fade due to the shuttling and sluggish conversion of polysulfides. Aiming at these problems, a biomimetic design of cofactor-assisted artificial enzyme catalyst, melamine (MM) crosslinked hemin on carboxylated carbon nanotubes (CNTs) (i.e., [CNTs–MM–hemin]), is presented to efficiently convert polysulfides. The MM cofactors bind with the hemin artificial enzymes and CNT conductive substrates through FeN₅ coordination and/or covalent amide bonds to provide high and durable catalytic activity for polysulfide conversions, while π–π conjugations between hemin and CNTs and multiple Li-bond networks offered by MM endow the cathode with good electronic/Li⁺ transmission ability. This synergistic mechanism enables rapid sulfur reaction kinetics, alleviated polysulfide shuttling, and an ultralow (<1.3%) loss of hemin active sites in electrolyte, which is ≈60 times lower than those of noncovalent crosslinked samples. As a result, the Li–S battery using [CNTs–MM–hemin] cathode retains a capacity of 571 mAh g⁻¹ after 900 cycles at 1C with an ultralow capacity decay rate of 0.046% per cycle. Even under raising sulfur loadings up to 7.5 mg cm⁻², the cathode still can steadily run 110 cycles with a capacity retention of 83%.

中文翻译：

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具有多个锂键网络的辅因子辅助人工酶可实现锂硫电池中可持续的多硫化物转化

锂硫电池具有较高的理论能量密度，但由于多硫化物的穿梭和转化缓慢，导致容量快速衰减。针对这些问题，提出了一种辅因子辅助人工酶催化剂——羧化碳纳米管（CNT）上三聚氰胺（MM）交联氯化血红素（即[CNTs-MM-氯化血红素]）的仿生设计，以有效地转化多硫化物。MM辅助因子通过FeN ₅配位和/或共价酰胺键与血红素人工酶和CNT导电底物结合，为多硫化物转化提供高且持久的催化活性，同时血红素和CNT之间的π - π共轭以及多个锂键网络提供MM赋予正极良好的电子/Li ⁺传输能力。这种协同机制实现了快速的硫反应动力学，减轻了多硫化物穿梭，并且电解质中氯化血红素活性位点的损失超低（<1.3%），比非共价交联样品的损失约低 60 倍。结果，使用[CNTs-MM-hemin]正极的Li-S电池在1C下循环900次后仍保持571 mAh g ^-1的容量，并且每个循环的容量衰减率为0.046%的超低容量。即使硫负载量提高到7.5 mg cm ^-2，正极仍然可以稳定运行110次循环，容量保持率为83%。