The Nanoscale Cryo-Microscopy of the Nucleation and Growth of Dendrites in Lithium-Ion Batteries

内部短路（ISC）是锂离子电池失效的主要原因，通常是由于枝晶的形成而发生的，尽管这些微观结构的成核和生长的实际机制尚不清楚。由于当前技术（如扫描电子显微镜（SEM））的限制，在纳米尺度上尤其如此。本研究项目的目的是展示一种新的冷冻显微镜装置的应用，即伦敦帝国理工学院的帝国材料冷冻显微镜中心（I(CM)2）。它具有结合低温透射电子显微镜（cryo-TEM）和低温原子探针断层扫描（cryo-APT）在亚原子尺度上研究枝晶成核的能力。当这些技术相互关联时，它们将分别提供有关局部化学的信息，特别是与降解有关的缺陷，以及高度分辨的原子排列组成图，从而绘制出比目前已知的更清晰的枝晶成核机制图像。众所周知，氢、碳、锂和硫等较轻的元素是推动电池技术发展的关键。然而，由于它们对光束损伤的敏感性以及与它们的量化相关的挑战，这些元素的研究存在明显的局限性。APT是一项不断发展的技术，在识别最轻的元素方面表现出几乎一致的能力，使其成为锂离子电池系统中应用的高潜力候选人。通过这一工作流程，我们可以更好地了解与枝晶成核和进化相关的局部化学和结构变化，这将提高我们对其机制和生长的理解。这些结果对于设计树突抑制措施和促进下一代lib的发展至关重要。工业和消费者也将受益于对ISCs根本原因的更好理解，这是当今电池技术的一个关键限制，也是全球研究人员致力于克服的挑战。该工作流程将用于研究环境温度变化、电解质成分、过量电流密度和荷电状态（SoC）对枝晶演化和化学的影响，这也将有助于提高我们对这些因素对电池退化的相互作用的理解。由于这个研究项目是第一个使用这种装置的项目之一，一个关键的方面将是为样品（电极）的制备、转移和表征制定合适的方案。这些信息可以用于后续的项目，特别是那些与能源材料有关的项目，而更一般的选址分析技术将有利于使用冷冻方法的更广泛的科学家。

Internal short-circuits (ISC) are a major cause of failure in lithium-ion batteries and typically occur due to the dendrite formation, although the actual mechanism of the nucleation and growth of these microstructures is still not well understood. This is especially true at the nanoscale due to the limitations presented by current techniques, such as scanning electron microscopy (SEM). The purpose of this research project is to present the application of a new cryo-microscopy set-up, the Imperial Centre for the Cryo-Microscopy of Materials (I(CM)2), at Imperial College London. This has the capability of combining cryo-transmission electron microscopy (cryo-TEM) with cryo-atom probe tomography (cryo-APT) to study dendrite nucleation at a sub-atomic scale. When correlated, these techniques will provide information on the local chemistry, particularly degradation-related defects, and a highly resolved compositional mapping of the atomic arrangement, respectively, thus painting a clearer image of the dendrite nucleation mechanism than what is currently known. It is well known that lighter elements, such as hydrogen, carbon, lithium and sulphur, have been key in advancing battery technology as we know it. Yet, due to their susceptibility to beam damage and challenges associated with their quantification, there are clear limitations associated with the study of such elements. APT is a growing technology that exhibits nearly uniform capabilities in identifying even the lightest of elements, making it a high-potential candidate in its application to lithium-ion battery systems. Achieving an improved understanding of the local chemistry and structural variations, made possible with this workflow, associated with dendrite nucleation and evolution will improve our understanding of their mechanism and growth. These results will subsequently be crucial in devising dendrite-suppression measures and contributing to the development of next-generation LIBs. Industry and consumers will also benefit from an improved understanding of the root causes of ISCs, a key limitation in battery technology today and a challenge that researchers globally are committed to overcoming. This workflow will be used to investigate the effects of ambient temperature variation, electrolyte composition, excess current density and state of charge (SoC) on dendrite evolution and chemistry, which will also help to improve our understanding of the interplay of these factors on battery degradation. As this research project is one of the first to use this set-up, a crucial aspect will be developing a suitable protocol for the sample (electrode) preparation, transfer and characterisation. This information can then be used for subsequent projects, particularly those relating to energy materials, while the more general site-selective analysis techniques will be beneficial to a wider reach of scientists using cryo-methods.