Song Chulho, Ito Kimihiko, Sakata Osami, Kubo Yoshimi
Global Research Center for Environment and Energy based on Nanomaterials Science (GREEN), National Institute for Materials Science (NIMS) 1-1 Namiki Tsukuba Ibaraki 305-0044 Japan
Synchrotron X-ray Station at SPring-8, Research Network and Facility Services Division, National Institute for Materials Science (NIMS) 1-1-1 Kouto, Sayo Hyogo 679-5148 Japan.
RSC Adv. 2018 Jul 23;8(46):26293-26299. doi: 10.1039/c8ra04855j. eCollection 2018 Jul 19.
Non-aqueous lithium-air batteries (LABs) attract attention as a candidate technology for next-generation energy storage devices. It is crucial to understand how the discharge product LiO is formed and decomposed by the electrochemical reactions to improve the cycle performance and decrease the charge voltage, which are the most important subjects for LAB development. Here, X-ray diffraction with high-brilliant X-rays in a transmission mode was used to observe the intensity and structural changes of crystalline LiO in an operating non-aqueous LAB in real time, and the Li-O electrochemical reaction involving LiO formation and decomposition was clearly demonstrated. The electrochemically formed LiO, which had an anisotropic domain size of 10 nm in the -direction and 40-70 nm in the -plane, grew due to the increase of the number of domains during the discharge process. No other reaction products with a crystalline phase such as LiOH were found in either the cathode or anode of the LAB, whereas the accelerated decomposition rate of the domains was accompanied with the change of the domain shape and lattice constant of the -axis in the latter half of the charge process with voltage higher than 4 V.
非水锂空气电池（LABs）作为下一代储能设备的候选技术备受关注。了解放电产物LiO如何通过电化学反应形成和分解对于提高循环性能以及降低充电电压至关重要，而这是LABs发展的最重要课题。在此，利用透射模式下的高亮度X射线进行X射线衍射，实时观察运行中的非水LAB中结晶LiO的强度和结构变化，清晰地展示了涉及LiO形成和分解的Li-O电化学反应。在放电过程中，电化学形成的LiO在c方向上的各向异性畴尺寸为10 nm，在ab平面上为40 - 70 nm，由于畴数量的增加而生长。在LAB的阴极或阳极中均未发现其他具有晶相的反应产物，如LiOH，而在充电过程的后半段，当电压高于4 V时，畴的加速分解速率伴随着畴形状和c轴晶格常数的变化。
