Wang Shenghong, Li Shiwen, Chen Xiaoqin, Yin Qianwen, Zhang Wang, Ning Yanxiao, Zhang Guohui, Fu Qiang
State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China.
SINOPEC (Dalian) Research Institute of Petroleum and Petrochemicals Co., Ltd., Dalian 116045, China.
J Am Chem Soc. 2025 Aug 20. doi: 10.1021/jacs.5c09519.
Solid electrolyte interphase (SEI) critically governs lithium (Li) battery performance. Yet, understanding the native SEI remains challenging due to the lack of techniques capable of depth profiling of the interphase layer under electrolyte conditions (wet-SEI). In this work, cryogenic X-ray photoelectron spectroscopy (cryo-XPS) coupled with argon gas cluster ion beam (GCIB) sputtering was developed to extensively investigate the vitrified wet-SEI of Li metal batteries without chemical damage. First, the combined cryo-XPS and GCIB platform captures the full composition of the native SEI in the presence of electrolyte, which comprises organic polymeric hydrocarbons and inorganic species like LiC, LiF, LiO, and LiCO. These results are significantly distinct from conventional XPS characterizations of dry-SEI (i.e., SEI without electrolyte) showing a depletion of inorganic species and thus highlight the strength of this hybrid approach in revealing the real motif of the native SEI. Second, a graded SEI architecture has been revealed with electrochemical decomposition products (LiF and LiCO) dominating the electrolyte-facing region, and chemically derived species (LiO and LiC) accumulating at the electrode-facing region. Lastly, this approach is capable of scrutinizing the dynamic evolution of SEI during Li deposition, unravelling a compositional shift from electrochemical SEI to a graded complex SEI architecture, with a thickness increase from the nanometer- to micrometer-scale. Therefore, depth-resolved cryo-XPS serves as a promising methodology for elucidating the dynamic heterogeneous chemical signatures across evolving solid-liquid interfaces in electrocatalysis and energy storage processes.
固态电解质界面（SEI）对锂电池性能起着关键作用。然而，由于缺乏能够在电解质条件下（湿SEI）对界面层进行深度剖析的技术，了解原生SEI仍然具有挑战性。在这项工作中，开发了结合低温X射线光电子能谱（cryo-XPS）和氩气团簇离子束（GCIB）溅射技术，以广泛研究锂金属电池的玻璃化湿SEI，且不会造成化学损伤。首先，cryo-XPS与GCIB相结合的平台能够在有电解质存在的情况下捕捉原生SEI的完整成分，其包括有机聚合碳氢化合物以及诸如LiC、LiF、LiO和LiCO等无机物种。这些结果与干SEI（即无电解质的SEI）的传统XPS表征显著不同，后者显示无机物种的耗尽，从而突出了这种混合方法在揭示原生SEI真实结构方面的优势。其次，揭示了一种梯度SEI结构，其中电化学分解产物（LiF和LiCO）在面向电解质的区域占主导，而化学衍生物种（LiO和LiC）在面向电极的区域积累。最后，这种方法能够仔细研究锂沉积过程中SEI的动态演变，揭示从电化学SEI到梯度复合SEI结构的成分转变，厚度从纳米级增加到微米级。因此，深度分辨cryo-XPS是一种很有前景的方法，可用于阐明电催化和能量存储过程中不断演变的固液界面上的动态异质化学特征。
