The solid–electrolyte interphase (SEI) formed on a battery electrode has been a central area of research for decades. This structurally complex layer profoundly impacts the electrochemical deposition morphology and stability of metal anodes. Departing from conventional approaches, we investigate metal dissolution—the reverse reaction of deposition—in battery environments using a state-of-the-art electroanalytical system combining a rotating-disk electrode and operando visualization. Our key finding is the presence of a transient SEI (T-SEI) that forms during fast discharging at high dissolution rates. We attribute T-SEI formation to local supersaturation and resultant electrolyte salt deposition. The T-SEI fundamentally alters the dissolution kinetics at the electrochemical interface, yielding a flat, clean surface. Unlike a classical SEI formed due to electrolyte decomposition, the T-SEI is “relaxable” upon removal of the enforced dissolution current; that is, the T-SEI dissolves back into the electrolyte when rested. The formation of T-SEI plays an unexpected critical role in the subsequent electrodeposition. When the metal is redeposited on a fully relaxed T-SEI surface, the morphology is remarkably different from that deposited on pristine or low-rate-discharged metal electrodes. Electron backscatter diffraction analysis suggests that the deposition occurs via growth of the original grains; this is in stark contrast to the isolated, new nuclei seen on standard metal electrodes without T-SEI formation. Using 3D profilometry, we observe a 42% reduction in surface roughness due to T-SEI formation. Our findings provide important insights into the kinetics at ion-producing electrochemical interfaces, and suggest a new dimension for engineering next generation batteries.

中文翻译：

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关于金属负极中隐藏的瞬态界面：动态沉淀控制电池中的电化学界面


几十年来，在电池电极上形成的固体-电解质界面 （SEI） 一直是研究的核心领域。这个结构复杂的层对金属阳极的电化学沉积形态和稳定性产生了深远的影响。与传统方法不同，我们使用结合旋转盘电极和原位可视化的最先进的电分析系统研究电池环境中的金属溶解——沉积的反向反应。我们的主要发现是在以高溶解速率快速放电过程中形成的瞬态 SEI （T-SEI）。我们将 T-SEI 的形成归因于局部过饱和和由此产生的电解质盐沉积。T-SEI 从根本上改变了电化学界面的溶出动力学，从而产生平坦、干净的表面。与由于电解质分解而形成的经典 SEI 不同，T-SEI 在去除强制溶解电流后是“可弛豫的”;也就是说，T-SEI 在休息时会溶解回电解液中。T-SEI 的形成在随后的电沉积中起着意想不到的关键作用。当金属重新沉积在完全松弛的 T-SEI 表面上时，其形态与沉积在原始或低速率放电金属电极上的形态明显不同。电子背散射衍射分析表明，沉积是通过原始晶粒的生长发生的;这与在没有形成 T-SEI 的标准金属电极上看到的孤立的新原子核形成鲜明对比。使用 3D 轮廓测量法，我们观察到由于 T-SEI 的形成，表面粗糙度降低了 42%。我们的研究结果为产生离子的电化学界面的动力学提供了重要的见解，并为设计下一代电池提出了新的维度。