Key Laboratory of Carbon Materials of Zhejiang Province, Wenzhou University, Wenzhou, 325035, China.
College of Electrical and Electronic Engineering, Wenzhou University, Wenzhou, 325035, China.
Adv Sci (Weinh). 2022 Jan;9(3):e2104205. doi: 10.1002/advs.202104205. Epub 2021 Nov 7.
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 FeN 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 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 , the cathode still can steadily run 110 cycles with a capacity retention of 83%.
锂硫电池具有高的理论能量密度，但由于多硫化物的穿梭和转化缓慢，其容量迅速衰减。针对这些问题，设计了一种仿生辅助因子的人工酶催化剂，三聚氰胺（MM）交联血红素接枝在羧基化碳纳米管（CNTs）上（即[CNTs-MM-hemin]），以有效地转化多硫化物。MM 辅助因子通过 FeN 配位和/或共价酰胺键与血红素人工酶和 CNT 导电基底结合，为多硫化物转化提供高且持久的催化活性，而血红素和 CNT 之间的π-π共轭以及 MM 提供的多个 Li 键网络赋予了阴极良好的电子/Li 传输能力。这种协同机制使硫反应动力学加快，缓解了多硫化物的穿梭，并使电解质中血红素活性位的损失率降低至约 1.3%（比非共价交联样品低约 60 倍）。结果，使用[CNTs-MM-hemin]阴极的 Li-S 电池在 1C 下经过 900 次循环后仍保持 571 mAh g 的容量，且每循环的容量衰减率低至 0.046%。即使在提高硫载量至 7.5 mg cm 时，阴极仍能稳定运行 110 次，容量保持率为 83%。
