Layered VS2 Nanosheet-Based Aqueous Zn Ion Battery Cathode
Layered VS2 Nanosheet-Based Aqueous Zn Ion Battery Cathode
复制标题
层状VS2纳米片基水系锌离子电池正极
DOI：
10.1002/aenm.201601920
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发表时间：
2017-06-07
影响因子：
27.8
通讯作者：
Mai, Liqiang
中科院分区：
文献类型：
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作者：
He, Pan;Yan, Mengyu;Mai, Liqiang
DOI：10.1002/aenm201601920类材料具有较大的层间距和较高的电导率，在多价离子(锌、镁、铝)的插入/提取方面显示出很大的潜力。在所有的TMDs中，VS2是典型的六方晶系TMDs家族成员，其晶体结构与石墨片相似，层间距为5.76ä。在VS2晶体结构中，每个V原子围绕6个S原子排列，并与S原子以共价键相连。VS2的层间距很大，可以方便地在电解液中插入/提取锂离子(0.69？)、钠离子(1.02？)、锌离子(0.74？)或它们的溶剂化鞘。然而，据我们所知，作为ZIB电极材料的VS2还没有报道。其中，VS2纳米片是通过简单的水热反应(支持信息)合成的，它在0.05A g−1的电流密度下提供了190.3 mA HG−1的高容量，并表现出长期的循环稳定性作为ZIB的阴极。通过X射线衍射仪(XRD)、X射线光电子能谱(XPS)、拉曼光谱、电子显微镜等测试手段，系统地研究了VS2电极的电化学反应机理。从各个方面都可以观察到可逆的插入/提取过程。电子显微镜和X射线衍射仪的离位结果都表明，VS2的层间距能够自适应锌离子的嵌入，沿c轴方向膨胀(仅1.73%)，而在a轴和b轴方向略有收缩，这对实现长寿命ZIB起到了关键作用。这些证据表明，VS2是一种具有高容量和良好循环稳定性的ZIBs正极材料。用X射线衍射仪对制备的VS2的晶体结构进行了测试。所有特征峰均符合VS2标准卡片(JCPDS编号01-089-1640)(图1a)。图1b显示了Vs2在100-1100 cm−1范围内的拉曼光谱。在140.4、192.0、282.0、406.6、687.8和993.2 cm−1处观察到6个峰，对应于V-VS2键或它们的组合的摇摆和伸缩振动。如图1c所示，VS2花由直径5-8微米、厚度50-100纳米的纳米片组装而成。根据选区电子衍射(SAED)图样计算的d间距分别为2.89和1.64ä(图2f)，分别与VS2的(002)和(110)晶面的d间距值相匹配。图2E中的透射电子显微镜和相应的高分辨电子显微镜图像显示了具有d-间隔为≈5.76？的VS2纳米片，
DOI: 10.1002/aenm. 201601920 class of materials show great potential for the insertion/extraction of multivalent ions (Zn2+, Mg2+, Al3+) owing to the characteristic of large layer spacing and high conductivity. Among all the TMDs, VS2 is a typical family member of TMDs with hexagonal system, which shows similar crystal structure to that of graphite lamellar with an interlayer spacing of 5.76 Å.[25, 30] There is a vanadium layer between two sulfur layers to form a kind of sandwich structure. In VS2 crystal structure, each V atom is arranged around six S atoms and connected with S atoms with covalent bonds. The interlayer spacing of VS2 is so large that enables the convenient insertion/extraction of lithium ions (0.69 Å), sodium ions (1.02 Å), zinc ions (0.74 Å) or their solvation sheath in electrolyte. However, to the best of our knowledge, there is no report about VS2 as the electrode materials for ZIBs.Herein, the VS2 nanosheets are synthesized via a facile hydrothermal reaction (Supporting Information), which deliver a high capacity of 190.3 mA hg− 1 at a current density of 0.05 A g− 1 and exhibit long-term cyclic stability as the cathode for ZIBs. The electrochemical reaction mechanism of such VS2 electrodes is further investigated systematically through a series of measurements including ex situ X-ray diffraction (XRD), ex situ X-ray photoelectron spectroscopy (XPS), in situ Raman, ex situ transmission electron microscopy (TEM). A reversible insertion/extraction process can be observed from all aspects. Both the ex situ TEM and ex situ XRD results demonstrate that the interlayer space of VS2 can self adapt to the intercalation of Zn2+ with an expansion along the c-axis (only 1.73%) and a slightly shrink along the a-and b-axes, which plays a key role in the realization of long-life ZIBs. All the above evidences reveal that the VS2 is a promising cathode material with high capacity and good cyclic stability for ZIBs. The crystal structure of the as-prepared VS2 is tested by XRD. All characteristic peaks are in accordance with the standard card of VS2 (JCPDS NO. 01-089-1640)(Figure 1a). The Raman spectrum of the VS2 in the range of 100–1100 cm− 1 is shown in Figure 1b. Six peaks located at 140.4, 192.0, 282.0, 406.6, 687.8, and 993.2 cm− 1 are observed, which correspond to the rocking and stretching vibrations of V–S bonds or their combination.[25] The morphology and microstructures of as-prepared VS2 are investigated by field emission scanning electron microscopy (SEM) and high-resolution TEM (HRTEM). As shown in Figure 1c, The VS2 flowers are assembled by nanosheets with a diameter of 5–8 µm and a thickness of 50–100 nm. The d-spacing calculated from selected area electron diffraction (SAED) patterns are 2.89 and 1.64 Å (Figure 2f), which match the d-spacing values of (002) and (110) crystal planes of VS2, respectively. TEM and corresponding HRTEM images in Figure 2e show VS2 nanosheets with a d-spacing of≈ 5.76 Å,