Depth-Dependent Understanding of Cathode Electrolyte Interphase (CEI) on the Layered Li-Ion Cathodes Operated at Extreme High Temperature
Depth-Dependent Understanding of Cathode Electrolyte Interphase (CEI) on the Layered Li-Ion Cathodes Operated at Extreme High Temperature
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DOI：
10.1021/acs.chemmater.2c00435
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发表时间：
2022-05
影响因子：
8.6
通讯作者：
Sudhan Nagarajan;C. Weiland;Sooyeon Hwang;M. Balasubramanian;L. Arava
中科院分区：
文献类型：
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作者：
Sudhan Nagarajan;C. Weiland;Sooyeon Hwang;M. Balasubramanian;L. Arava
锂离子电池的高温运行高度依赖于锂化-脱锂反应过程中形成的阴极电解质界面（CEI）的稳定性。然而，关于 CEI 性质的知识有限，其在极端温度下的稳定性尚不清楚。因此，本文中，我们研究了使用热稳定吡咯烷基离子液体电解质在 100 °C 极端操作条件下稳定模型 LiNi0.33Mn0.33Co0.33O2(NMC333) 的 CEI 的概念验证研究。研究了 100 °C 下的电化学锂化-脱锂反应以及不同循环条件下的 CEI 演变。此外，使用基于能量可调谐同步加速器的硬 X 射线光电子能谱 (HAXPES) 研究了深度依赖的 CEI 化学。结果表明，与室温相比，高温操作加速了CEI的形成，并且界面层表面比更深的表面富含硼基无机部分。此外，体敏X射线吸收光谱（XAS）被用来研究高温电化学反应过程中过渡金属氧化还原的贡献者；与室温类似，Ni2+/4+氧化还原对是高温操作期间唯一的电荷补偿氧化还原对。最后，利用高分辨率透射电子显微镜观察了阴极颗粒上的共形 CEI 的物理性质，这证实了没有共形 CEI 的阴极颗粒的显着降解是由于在极端温度下层状结构转变为尖晶石结构所致。在这项研究中，通过先进的光谱学和显微镜了解 NMC 阴极的高温界面化学将为将常温锂离子化学转化为高温应用提供线索。
The high-temperature operation of Li-ion batteries is highly dependent on the stability of the cathode electrolyte interphase (CEI) formed during lithiation–delithiation reactions. However, knowledge on the nature of the CEI is limited and its stability under extreme temperatures is not well understood. Therefore, herein, we investigate a proof-of-concept study on stabilizing CEI on model LiNi0.33Mn0.33Co0.33O2(NMC333) at an extreme operation condition of 100 °C using the thermally stable pyrrolidinium-based ionic liquid electrolyte. The electrochemical lithiation–delithiation reactions at 100 °C and the CEI evolution upon different cycling conditions are investigated. Further, the depth-dependent CEI chemistry was investigated using energy-tunable synchrotron-based hard X-ray photoelectron spectroscopy (HAXPES). The results reveal that the high-temperature operation accelerated the CEI formation compared to room temperature, and the surface of the interphase layer is rich in boron-based inorganic moieties than the deeper surface. Further, bulk-sensitive X-ray absorption spectroscopy (XAS) was used to investigate the transition-metal redox contributors during high-temperature electrochemical reactions; similar to room temperature, the Ni2+/4+redox couple is the only charge-compensating redox couple during high-temperature operation. Finally, the physical nature of the conformal CEI on the cathode particles was visualized with high-resolution transmission electron microscopy, which confirms that the significant degradation of cathode particles without conformal CEI is due to the transformation of a layer-to-spinel formation at extreme temperature. In this study, understanding this high-temperature interfacial chemistry of NMC cathodes through advanced spectroscopy and microscopy will shed light on transforming the ambient-temperature Li-ion chemistry into high-temperature applications.