Oxygen bridges between NiO nanosheets and graphene for improvement of lithium storage.
Oxygen bridges between NiO nanosheets and graphene for improvement of lithium storage.
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DOI：
10.1021/nn300098m
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发表时间：
2012-03
期刊：
影响因子：
17.1
通讯作者：
Guangmin Zhou;Da‐Wei Wang;L. Yin;Na Li;Feng Li;Hui‐Ming Cheng
中科院分区：
文献类型：
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作者：
Guangmin Zhou;Da‐Wei Wang;L. Yin;Na Li;Feng Li;Hui‐Ming Cheng
石墨烯已被广泛用于显著提高几乎任何电池电极材料的容量、倍率能力和循环性能。然而，石墨烯与这些电极材料之间的结合还没有被清楚地阐明。本文通过X射线光电子能谱、傅里叶变换红外光谱和拉曼光谱的分析，报道了含氧官能团的石墨烯与NiO之间的氧桥，并通过第一性原理计算确认了氧桥的构象。我们发现NiO纳米片(NiO NSS)通过氧桥与石墨烯紧密结合。氧桥主要来源于石墨烯上的羟基/环氧基团钉扎在NiO-NSS的Ni原子上。计算得到含氧石墨烯上镍原子与氧结合的吸附能分别为1.37 eV和1.84 eV，与石墨烯上的1.26 eV相当。然而，镍原子在氧化的石墨烯表面的扩散势垒(含羟基和环氧基的石墨烯分别为2.23和1.69 eV)远大于在石墨烯表面的扩散势垒(0.19 eV)。因此，NiO NS通过C-O-Ni桥牢固地固定在石墨烯上，具有高的可逆容量和优异的倍率性能。氧化后的石墨烯上Ni原子的易结合/难解离特性促进了电子从石墨烯到NiO的快速跃迁，从而促进了NiO的可逆锂化和脱氢反应。我们相信，对石墨烯和NiO之间这种氧桥的了解将导致其他高性能电极材料的发展。
Graphene has been widely used to dramatically improve the capacity, rate capability, and cycling performance of nearly any electrode material for batteries. However, the binding between graphene and these electrode materials has not been clearly elucidated. Here we report oxygen bridges between graphene with oxygen functional groups and NiO from analysis by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and Raman spectroscopy and confirm the conformation of oxygen bridges by the first-principles calculations. We found that NiO nanosheets (NiO NSs) are bonded strongly to graphene through oxygen bridges. The oxygen bridges mainly originate from the pinning of hydroxyl/epoxy groups from graphene on the Ni atoms of NiO NSs. The calculated adsorption energies (1.37 and 1.84 eV for graphene with hydroxyl and epoxy) of a Ni adatom on oxygenated graphene by binding with oxygen are comparable with that on graphene (1.26 eV). However, the calculated diffusion barriers of the Ni adatom on the oxygenated graphene surface (2.23 and 1.69 eV for graphene with hydroxyl and epoxy) are much larger than that on the graphene (0.19 eV). Therefore, the NiO NS is anchored strongly on the graphene through a C-O-Ni bridge, which allows a high reversible capacity and excellent rate performance. The easy binding/difficult dissociating characteristic of Ni adatoms on the oxygenated graphene facilitates fast electron hopping from graphene to NiO and thus the reversible lithiation and delithiation of NiO. We believe that the understanding of this oxygen bridge between graphene and NiO will lead to the development of other high-performance electrode materials.