Kakimi Tomohiro, Miyakawa Shuntaro, Taminato Sou, Saito Takaya, Mori Daisuke, Imanishi Nobuyuki
Department of Chemistry for Materials, Graduate School of Engineering, Mie University Tsu Mie 514-8507 Japan
Advanced Battery Research Office, Research Institute of Advanced Technology, SoftBank Corporation Kaigan, Minato-Ku Tokyo 105-7529 Japan.
RSC Adv. 2023 Mar 20;13(14):9142-9153. doi: 10.1039/d2ra08027c.
Lithium metal anodes show great promise for use in next-generation secondary batteries, but they suffer from lithium dendrite growth, as well as other issues, which cause safety problems and result in a loss of capacity with time. The use of artificial inorganic solid electrolyte interphase (SEI) layers, such as those comprising AlO, is a promising way to mitigate these disadvantages, but the mechanism behind these observed improvements remains poorly understood. Therefore, in this study, using pulsed laser deposition (PLD), the surface of a Cu electrode was coated with a physicochemically stable and mechanically strong AlO thin film, and the effects of the film coating on the lithium deposition and dissolution behaviour were investigated. When the morphology of the deposits was evaluated by scanning electron microscopy, small lithium nuclei (approximately 0.2 μm in diameter) were observed to be deposited uniformly over the entire surface of the uncoated Cu electrode in the initial electrodeposition, and these grew into needle-like crystals from the nuclei. After 60 min of electrodeposition, the needle-like precipitates had aggregated and grown into three-dimensional structures with dendritic form. In contrast, on the surface of the Cu electrode modified with AlO by PLD for 1 h, lithium clusters of about 50 μm in diameter were found to be aggregated and precipitated in the initial stages of electrodeposition. Notably, this is the first report of lithium deposition on AlO thin films. With further cycling, the precipitates grew into two-dimensional flat plates. Analysis of the SEI film formed during the first deposition reaction revealed that the AlO coating reduced the thickness of the SEI compared to that of the uncoated electrode. Therefore, the AlO coating suppressed the decomposition of the electrolyte with the Cu electrode. The use of AlO coatings results in (i) the growth of two-dimensional lithium clusters with an island shape on the AlO thin film, and these could ensure a uniform electron conduction path to the electrode; in addition, (ii) the inhibited electrolyte decomposition caused by the low-surface-area lithium clusters and the low electronic conductivity of the AlO thin film. These improve the coulombic efficiency and cycling behaviour.
锂金属阳极在下一代二次电池的应用中展现出巨大潜力，但它们存在锂枝晶生长以及其他问题，这些问题会引发安全隐患并导致容量随时间损失。使用人工无机固体电解质界面（SEI）层，例如由AlO组成的那些，是减轻这些缺点的一种有前景的方法，但这些观察到的改进背后的机制仍知之甚少。因此，在本研究中，使用脉冲激光沉积（PLD）在铜电极表面涂覆了一层物理化学稳定且机械强度高的AlO薄膜，并研究了薄膜涂层对锂沉积和溶解行为的影响。当通过扫描电子显微镜评估沉积物的形态时，在初始电沉积过程中，观察到小的锂核（直径约0.2μm）均匀地沉积在未涂覆铜电极的整个表面上，并且这些锂核从核生长成针状晶体。电沉积60分钟后，针状沉淀物聚集并生长成具有树枝状形态的三维结构。相比之下，在通过PLD用AlO改性1小时的铜电极表面上，发现在电沉积的初始阶段直径约50μm的锂簇聚集并沉淀。值得注意的是，这是关于锂在AlO薄膜上沉积的首次报道。随着进一步循环，沉淀物生长成二维平板。对第一次沉积反应期间形成的SEI膜的分析表明，与未涂覆电极相比，AlO涂层减小了SEI的厚度。因此，AlO涂层抑制了电解质与铜电极的分解。使用AlO涂层导致（i）在AlO薄膜上生长出具有岛状形状的二维锂簇，这些锂簇可以确保通向电极的均匀电子传导路径；此外，（ii）由低表面积锂簇和AlO薄膜的低电子电导率引起的电解质分解受到抑制。这些提高了库仑效率和循环性能。
