Exposed facet engineering design of graphene-SnO2 nanorods for ultrastable Li-ion batteries
Exposed facet engineering design of graphene-SnO2 nanorods for ultrastable Li-ion batteries
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DOI：
10.1016/j.ensm.2018.10.007
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发表时间：
2019-05-01
影响因子：
20.4
通讯作者：
Wang, Xi
中科院分区：
文献类型：
--
作者：
Pan, Lu;Zhang, Yihui;Wang, Xi
制备锂离子电池(LiBS)用超稳电极材料的方法有很多，但通过裸露的小面工程方法设计出具有应用前景的电极材料是有效的，但仍具有挑战性。在这里，石墨烯-SnO2材料由于其较高的理论容量和导电性而被选为潜在的候选材料。本文首次用从头算密度泛函理论(DFT)计算了具有不同曝光面的SnO2材料的可能性质：(211)面与其它面相比具有较高的表面能和较低的Li+势垒。然后利用晶间距匹配法制备了具有高度暴露的(211)面的石墨烯-SnO2纳米棒(GSN-211)。作为锂离子电池负极材料，GSN-211确实表现出了很好的电化学性能：超稳循环稳定性(500次循环后0.2A/g时为695mAhg)和出色的倍率性能(5A/g时为530mAhg)。利用原子水平的原位电子显微镜，进一步观察了GSN-211在(211)晶面上的各向异性输运和原子尺度的跃迁行为，观察到了(211)晶面上的锡/氧原子的剥离。这表明(211)晶面对锂离子的插入具有很高的活性中心，导致锂离子的快速存储。结合理论计算，探讨了GSN-211在锂化过程中的原子力学性能：体积弹性模量的降低意味着初始锂化态后GSN-211的软化，结构稳定性较好。这些发现为利用裸露小平面工程方法进行LIBS的先进阳极设计提供了一个新的视角。
Many routes are developed to prepare ultrastable electrode materials for Li-ion batteries (LIBs), whereas it is effective but still challenge to design promising ones through exposed facet engineering route. Here, graphene-SnO2 material is selected as a potential candidate due to its high theoretical capacity and conductivity. The ab initio density functional theory (DFT) calculations are firstly used here to predict the possible property of SnO2 materials with different exposed facets: (211) facet is found to have the relatively high surface energy and a lower energy barrier towards Li+ when compared with other planes. Then the graphene-SnO2 nanorods with highly exposed (211) facets (GSn-211) is fabricated by utilizing a crystalline-spacing-matching method. When tested as anode for LIBs, GSn-211 indeed shows a great electrochemical property: ultrastable cycling stability (695 mAh/g at 0.2 A/g after even 500 cycles) and an outstanding rate capability (530 mAh/g at 5 A/g). The Li-ions anisotropic transport and the atomic-scale ledged behaviors of GSn-211 along (211) are further visualized via an in situ TEM at atomic level, in which the Sn/O atoms-peeling-off through (211) facet is observed. This indicates (211) planes hold high active sites towards Li-ions insertion, leading to a fast Li+ storage. Combined with theoretical calculations, their atomistic mechanical properties during lithiation are explored: the decrease of bulk modulus means the GSn-211 is softened after the initial lithiated state leads to better structural stability. These findings provide a novel perspective for the advanced anode design for LIBs via the exposed facet engineering method.