Electrochemical Growth of Very Long (∼80 μm) Crystalline Li2O2 Nanowires on Single-Layer Graphene Covered Gold and Their Growth Mechanism,Journal of the American Chemical Society

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Electrochemical Growth of Very Long (∼80 μm) Crystalline Li2O2 Nanowires on Single-Layer Graphene Covered Gold and Their Growth Mechanism
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2020-10-20 , DOI: 10.1021/jacs.0c05392
Kentaro Tomita ₁ , Hidenori Noguchi ₁ , Kohei Uosaki ₁

Affiliation

For the development of lithium-air battery (LAB), which is one of the most promising next generation batteries, it is essential to understand the structure and properties of Li2O2, which is the discharged product at the positive electrode of a LAB, as well as the mechanism of Li2O2 growth because its deposition limits the discharge capacity and is the origin of the high charging overpotential of LAB. Characterization of the structure and properties of the Li2O2 formed in LABs is, however, difficult because it is usually in the form of poorly ordered small particles. In this study, we successfully grew well-aligned very long (∼80 μm) crystalline Li2O2 nanowires (NWs: average diameter of 22 nm) electrochemically at a gold electrode covered with single-layer graphene (SLG/Au). Preferential growth of the NWs along c-axis was confirmed by X-ray diffraction, transmission electron microscopy with electron diffraction, and Raman scattering. Raman imaging indicated that the sites of NW growth were the grain boundaries of single-layer graphene. The long, crystalline Li2O2 NWs provided the opportunity to investigate not only their structure and properties but also their growth mechanism during discharge. Raman measurements in the O-O stretching frequency region of the SLG/Au electrode at various depths of the discharge combined with exchange of oxygen in the solution from 18O2 to 16O2 during the discharge revealed that the growth took place at the bottom of the NWs, i.e., the Li2O2/electrode interface, not the top of the NWs, i.e., the solution/Li2O2 interface. This growth mechanism can explain why such long NWs can be grown despite the insulating nature of Li2O2.

中文翻译：

单层石墨烯包覆金上极长（~80 μm）结晶 Li2O2 纳米线的电化学生长及其生长机制

锂空气电池（LAB）是最有前途的下一代电池之一，要开发锂空气电池（LAB），必须了解锂空气电池正极放电产物Li2O2的结构和性质，以及作为 Li2O2 生长的机制，因为它的沉积限制了放电容量，并且是 LAB 高充电过电位的起源。然而，表征 LAB 中形成的 Li2O2 的结构和性质是困难的，因为它通常是有序性较差的小颗粒形式。在这项研究中，我们成功地在覆盖有单层石墨烯（SLG/Au）的金电极上电化学生长了排列良好的非常长（~80 μm）的结晶 Li2O2 纳米线（NW：平均直径为 22 nm）。通过 X 射线衍射、具有电子衍射的透射电子显微镜和拉曼散射证实了 NW 沿 c 轴的优先生长。拉曼成像表明 NW 生长的位置是单层石墨烯的晶界。长晶状 Li2O2 NW 不仅为研究它们的结构和性质提供了机会，还提供了研究它们在放电过程中的生长机制的机会。SLG/Au 电极在不同放电深度的 OO 拉伸频率区域中的拉曼测量与放电过程中溶液中氧从 18O2 到 16O2 的交换表明生长发生在 NW 的底部，即， Li2O2/电极界面，而不是 NW 的顶部，即溶液/Li2O2 界面。

更新日期：2020-10-20

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