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Probing the Thermal-Driven Structural and Chemical Degradation of Ni-Rich Layered Cathodes by Co/Mn Exchange
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2020-11-04 , DOI: 10.1021/jacs.0c09961
Xiang Liu 1 , Gui-Liang Xu 1 , Liang Yin 2 , Inhui Hwang 2, 3 , Yan Li 4 , Languang Lu 4 , Wenqian Xu 2 , Xuequan Zhang 5 , Yanbin Chen 5 , Yang Ren 2 , Cheng-Jun Sun 2 , Zonghai Chen 1 , Minggao Ouyang 4 , Khalil Amine 1, 6, 7
Affiliation  

The intrinsic poor thermal stability of layered LiNixCoyMn1-x-yO2 (NCM) cathodes and the exothermic side reactions triggered by the associated oxygen release are the main safety threats for their large-scale implantation. In the NCM family, it is widely accepted that Ni is the stability troublemaker, while Mn has long been considered as a structure stabilizer, whereas the role of Co remains elusive. Here, via Co/Mn exchange in a Ni-rich LiNi0.83Co0.11Mn0.06O2 cathode, we demonstrate that the chemical and structural stability of the deep delithiated NCM cathodes are significantly dominated by Co rather than the widely reported Mn. Operando synchrotron X-ray characterization coupling with in situ mass spectrometry reveal that the Co4+ reduces prior to the reduction of Ni4+ and could thus prolong the Ni migration by occupying the tetrahedra sites and, hence, postpone the oxygen release and thermal failure. In contrast, the Mn itself is stable, but barely stabilizes the Ni4+. Our results highlight the importance of evaluating the intrinsic role of compositional tuning on the Ni-rich/Co-free layered oxide cathode materials to guarantee the safe operation of high-energy Li-ion batteries.

中文翻译:

通过 Co/Mn 交换探索富镍层状阴极的热驱动结构和化学降解

层状 LiNixCoyMn1-x-yO2 (NCM) 阴极固有的热稳定性差以及相关的氧释放引发的放热副反应是其大规模植入的主要安全威胁。在 NCM 家族中,人们普遍认为 Ni 是稳定性问题的制造者,而 Mn 长期以来被认为是结构稳定剂,而 Co 的作用仍然难以捉摸。在这里,通过富镍 LiNi0.83Co0.11Mn0.06O2 正极中的 Co/Mn 交换,我们证明了深度脱锂 NCM 正极的化学和结构稳定性主要由 Co 主导,而不是广泛报道的 Mn。与原位质谱联用的原位同步加速器 X 射线表征表明 Co4+ 在 Ni4+ 还原之前减少,因此可以通过占据四面体位点来延长 Ni 迁移,并且,因此,推迟氧气释放和热失效。相比之下,Mn 本身是稳定的,但几乎不能稳定 Ni4+。我们的结果强调了评估成分调整对富镍/无钴层状氧化物正极材料的内在作用的重要性,以保证高能锂离子电池的安全运行。
更新日期:2020-11-04
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