Hierarchical Microtubes Constructed by MoS₂ Nanosheets with Enhanced Sodium Storage Performance

Emerging sodium-ion batteries (SIBs) have aroused great attention in large-scale energy storage. However, it is still a great challenge to develop suitable electrode materials due to the large radius of Na⁺. This work demonstrates a strategy to synthesize hierarchical tubular MoS₂ via a facial hydrothermal method with the assistance of tetramethylammonium bromide (TMAB). The results show that sufficient amounts of TMA⁺ ions are necessary to form the hierarchical tubular structures of MoS₂. The obtained tubular MoS₂ displays a high diffusion coefficient of Na⁺ ions, a high specific capacity of 652.5 mAh/g at the current density of 100 mA/g after 50 cycles, and a good cycling stability (94.2% of the initial capacity can be retained after 100 cycles at 1000 mA/g). In situ XRD during the discharge/charge process displays a reversible intercalation/deintercalation of Na⁺ into MoS₂ layers followed by a conversion-type reaction. Systematic analyses reveal that the enhanced electrochemical performance is attributed to its tubular hierarchical structures with the wall composed of loosely stacked nanosheets, which can provide nearly unobstructed ion transportation paths, sufficient active sites, and enough space to mitigate the effects of the volume change during the discharge/charge process. This synthetic approach can be easily extended to other metal oxides and metal sulfides with hierarchical structures for versatile applications.