Hierarchical\nMicrotubes Constructed by MoS₂ Nanosheets with Enhanced\nSodium Storage Performance

Abstract

Emerging\nsodium-ion batteries (SIBs) have aroused great attention\nin large-scale energy storage. However, it is still a great challenge\nto develop suitable electrode materials due to the large radius of\nNa⁺. This work demonstrates a strategy to synthesize hierarchical\ntubular MoS₂ <i>via</i> a facial hydrothermal\nmethod with the assistance of tetramethylammonium bromide (TMAB).\nThe results show that sufficient amounts of TMA⁺ ions are\nnecessary to form the hierarchical tubular structures of MoS₂. The obtained tubular MoS₂ displays a high diffusion\ncoefficient of Na⁺ ions, a high specific capacity of 652.5\nmAh/g at the current density of 100 mA/g after 50 cycles, and a good\ncycling stability (94.2% of the initial capacity can be retained after\n100 cycles at 1000 mA/g). <i>In situ</i> XRD during the\ndischarge/charge process displays a reversible intercalation/deintercalation\nof Na⁺ into MoS₂ layers followed by a conversion-type\nreaction. Systematic analyses reveal that the enhanced electrochemical\nperformance is attributed to its tubular hierarchical structures with\nthe wall composed of loosely stacked nanosheets, which can provide\nnearly unobstructed ion transportation paths, sufficient active sites,\nand enough space to mitigate the effects of the volume change during\nthe discharge/charge process. This synthetic approach can be easily\nextended to other metal oxides and metal sulfides with hierarchical\nstructures for versatile applications.