Sodium-ion battery technology is a promising alternative to lithium-ion batteries for low-cost and large-scale energy storage applications. The larger size of the Na-ion relative to the Li-ion imposes kinetic limitations and often results in sluggish Na-ion diffusion. It is a great necessity to explore prominent structural features of materials to overcome the limitations and improve the diffusion. Layered MoS₂ has an ideal two-dimensional diffusion pathway because of the weak van der Waals interaction between the layers. However, the limited gallery height of 0.3 nm is insufficient to achieve fast Na-ion diffusion. A facile hydrothermal route at medium-ranged temperatures is reported in this work to obtain interlayer expanded MoS₂ nanosheets. The interlayer spacing is greatly expanded to 1 nm and facilitates Na-ion insertion and extraction in the van der Waals gaps. The nanosheet morphology shortens the Na-ion diffusion distance from the lateral side. The interlayer expanded MoS₂ nanosheets are used as sodium-ion battery anodes in the voltage window of 0.5–2.8 V, where intercalation reaction contributes to Na storage and the layered structure can be preserved. The nanosheets exhibit a high cycling stability by retaining 92% of the initial charge capacity after 100 cycles and a great rate capability of 43 mA h g⁻¹ at 2 A g⁻¹. Kinetics study reveals a significant alleviation of diffusional limitation, verifying the improved Na-ion diffusion and enhanced Na storage. The presented work explores the utilization of the van der Waals gaps to store ions and sheds light on designing two-dimensional materials in other energy systems.

中文翻译：

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MoS ₂纳米片具有增加的层间间距，可增强钠的储藏能力†

对于低成本和大规模储能应用，钠离子电池技术是锂离子电池的有前途的替代方法。Na离子相对于Li离子的较大尺寸强加了动力学限制，通常会导致Na离子扩散缓慢。探索材料的突出结构特征以克服局限性并改善扩散是非常必要的。层状MoS ₂具有理想的二维扩散途径，这是因为层之间的范德华相互作用较弱。但是，有限的0.3 nm画廊高度不足以实现快速的Na离子扩散。在这项工作中报道了一种在中等温度下的简便热液路线，以获得层间膨胀的MoS ₂纳米片。层间间距大大扩展到1 nm，并促进了范德华间隙中Na离子的插入和提取。纳米片的形态缩短了Na离子从侧面的扩散距离。层间扩展的MoS ₂纳米片用作0.5-2.8 V的电压窗口中的钠离子电池阳极，其中插层反应有助于Na的储存，并且可以保留层状结构。通过在100次循环后保留92％的初始充电容量，纳米片表现出高循环稳定性，并在2 A g ^-1下具有43 mA hg ^-1的大倍率能力。动力学研究揭示了扩散限制的显着缓解，证实了改善的Na离子扩散和增强的Na储存。提出的工作探索了范德华间隙的利用来存储离子，并为设计其他能源系统中的二维材料提供了启示。