Herein, we present a detailed investigation of the electrochemically triggered formation and dissolution processes of α- and β-sulfur crystals on a monolithic carbon cathode using operando high-resolution synchrotron radiography (438 nm/pixel). The combination of visual monitoring with the electrical current response during cyclic voltammetry provides valuable insights into the sulfur formation and dissolution mechanism. Our observations show that the crystal growth process is mainly dictated by a rapid equilibrium between long-chain polysulfides on one side and solid sulfur/short-chain polysulfides on the other side, which is consistent with previous studies in this field. The high temporal and spatial resolution of synchrotron imaging enables the observation of different regimes during the sulfur formation and dissolution process. The appearance of short-chain polysulfides after the first anodic CV peak initiates a rapid dissolution process of α-sulfur crystals on the cathode. The increase in the long-chain lithium polysulfide concentration at the cathode surface during charge results in an increased crystal growth rate, which in turn produces imperfections in α- and β-sulfur crystals. There are strong indications that these defects are fluid inclusions, which may trap dissolved polysulfides and therefore reduce the electrochemical cell capacity.

中文翻译：

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用同步加速器成像对Li-S电池进行Operando分析期间，硫磺晶体演化的详细而直接的观察。

本文中，我们对使用操作法在整体碳阴极上的α-和β-硫晶体的电化学触发形成和溶解过程进行了详细的研究。高分辨率同步辐射照相（438 nm /像素）。视觉伏安与循环伏安法中的电流响应相结合，为了解硫的形成和溶解机理提供了宝贵的见识。我们的观察表明，晶体生长过程主要由一侧的长链多硫化物与另一侧的固体硫/短链多硫化物之间的快速平衡决定，这与该领域以前的研究一致。同步加速器成像的高时间和空间分辨率使得能够观察到硫形成和溶解过程中的不同状态。在第一个阳极CV峰之后出现短链多硫化物，引发了α-硫晶体在阴极上的快速溶解过程。充电过程中阴极表面长链多硫化锂的浓度增加导致晶体生长速率增加，进而在α和β硫晶体中产生缺陷。有充分的迹象表明这些缺陷是流体包裹体，它们可能会捕获溶解的多硫化物，从而降低电化学电池的容量。