Lithium metal has been considered the “holy grail” anode material for rechargeable batteries despite the fact that its dendritic growth and low Coulombic efficiency (CE) have crippled its practical use for decades. Its high chemical reactivity and low stability make it difficult to explore the intrinsic chemical and physical properties of the electrochemically deposited lithium (EDLi) and its accompanying solid electrolyte interphase (SEI). To prevent the dendritic growth and enhance the electrochemical reversibility, it is crucial to understand the nano- and mesostructures of EDLi. However, Li metal is very sensitive to beam damage and has low contrast for commonly used characterization techniques such as electron microscopy. Inspired by biological imaging techniques, this work demonstrates the power of cryogenic (cryo)-electron microscopy to reveal the detailed structure of EDLi and the SEI composition at the nanoscale while minimizing beam damage during imaging. Surprisingly, the results show that the nucleation-dominated EDLi (5 min at 0.5 mA cm^–2) is amorphous, while there is some crystalline LiF present in the SEI. The EDLi grown from various electrolytes with different additives exhibits distinctive surface properties. Consequently, these results highlight the importance of the SEI and its relationship with the CE. Our findings not only illustrate the capabilities of cryogenic microscopy for beam (thermal)-sensitive materials but also yield crucial structural information on the EDLi evolution with and without electrolyte additives.

中文翻译：

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低温TEM对电化学沉积锂金属及其固体电解质间相结构的新认识。

尽管锂金属的树枝状生长和低库仑效率（CE）削弱了其数十年的实际应用，但它仍被视为可再充电电池的“圣杯”负极材料。它的高化学反应性和低稳定性使其难以研究电化学沉积的锂（EDLi）及其随附的固体电解质中间相（SEI）的固有化学和物理性质。为了防止树枝状晶体生长并增强电化学可逆性，了解EDLi的纳米结构和介孔结构至关重要。但是，锂金属对电子束损伤非常敏感，并且对于诸如电子显微镜之类的常用表征技术而言对比度较低。受生物成像技术的启发，这项工作证明了低温（低温）电子显微镜能够揭示纳米级EDLi和SEI成分的详细结构，同时最大程度地减少了成像过程中的光束损伤。出乎意料的是，结果表明，以成核为主的EDLi（在0.5 mA cm下持续5分钟）^–2）是非晶态的，而SEI中存在一些结晶LiF。由各种电解质和不同的添加剂制成的EDLi表现出独特的表面性能。因此，这些结果凸显了SEI及其与CE的关系的重要性。我们的发现不仅说明了低温显微镜对束状（热）敏感材料的功能，而且还提供了有关添加和不添加电解质添加剂的EDLi演变的关键结构信息。