Revealing Grain-Boundary-Induced Degradation Mechanisms in Li-Rich Cathode Materials
Revealing Grain-Boundary-Induced Degradation Mechanisms in Li-Rich Cathode Materials
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DOI：
10.1021/acs.nanolett.9b04620
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发表时间：
2020-02-01
期刊：
影响因子：
10.8
通讯作者：
Shahbazian-Yassar, Reza
中科院分区：
文献类型：
--
作者：
Sharifi-Asl, Soroosh;Yurkiv, Vitaliy;Shahbazian-Yassar, Reza
XLi(2)MnO(3)中心点(1-x)LiTMO2(Tm=Ni，Mn，Co)(LMR-NMC)(LMR-NMC)阴极虽然能量密度高，但仍需进一步开发，以克服与体相和表面不稳定性有关的问题，如锰的溶解、阻抗升高和电压衰减。改变LMR-NMC性能的一个很有前途的策略是结合尖晶石型的局部结构域来创建“层状-层状-尖晶石”阴极。然而，精确控制局部结构和组成，以及随后对这类材料的表征，是具有挑战性的，阐明结构-性质关系并不是微不足道的。因此，对这些材料内部原子结构的详细研究对它们的发展仍然至关重要。在这里，像差校正扫描电子显微镜(AC-STEM)被用来研究具有集成尖晶石型成分的LMR-NMC材料在电化学循环前后的原子结构。结果表明，存在各种原子构型的应变晶界，包括尖晶石型结构。这些高能晶界似乎通过增加与电解液的接触表面积以及在循环过程中镍的迁移来诱导裂纹和促进锰的溶解，从而加速性能退化。这些结果揭示了局部结构在阴极结构宏观退化中的重要作用，并重申了合成和组成如何影响先进阴极设计的结构-电化学性质关系的复杂性。
Despite their high energy densities, Li- and Mn-rich, layered-layered, xLi(2)MnO(3)center dot(1 - x)LiTMO2 (TM = Ni, Mn, Co) (LMR-NMC) cathodes require further development in order to overcome issues related to bulk and surface instabilities such as Mn dissolution, impedance rise, and voltage fade. One promising strategy to modify LMR-NMC properties has been the incorporation of spinel-type, local domains to create "layered- layered-spinel" cathodes. HoweVer, precise control of local structure and composition, as well as subsequent characterization of such materials, is challenging and elucidating structure-property relationships is not trivial. Therefore, detailed studies of atomic structures within these materials are still critical to their development. Herein, aberration corrected-scanning transmission electron microscopy (AC-STEM) is utilized to study atomic structures, prior to and subsequent to electrochemical cycling, of LMR-NMC materials having integrated spinel-type components. The results demonstrate that strained grain boundaries with various atomic configurations, including spinel-type structures, can exist. These high energy boundaries appear to induce cracking and promote dissolution of Mn by increasing the contact surface area to electrolyte as well as migration of Ni during cycling, thereby accelerating performance degradation. These results present insights into the important role that local structures can play in the macroscopic degradation of the cathode structures and reiterate the complexity of how synthesis and composition affect structure-electrochemical property relationships of advanced cathode designs.