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Seo, Dong-Hwa
Computational Energy Materials Science Lab
Research Interests
  • 본 연구실에서는 제일원리 (first-principles) 전산모사 기법을 통해 이차전지용 전극 소재와 고체 전해질 소재에 대해 원자 단위에서 깊이 있게 이해하고 이를 바탕으로 신규 소재를 개발하고 기존 소재의 성능 향상시키는 연구를 진행하고 있습니다. 또한 인공지능 (artificial intelligence)과 기계학습 (Machine learning), 로봇공학 (robotics)을 조합하여 자동 합성/분석을 통한 재료 개발에 대한 연구를 진행하고 있습니다.

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Revealing the structural degradation mechanism of the Ni-rich cathode surface: How thick is the surface?

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Title
Revealing the structural degradation mechanism of the Ni-rich cathode surface: How thick is the surface?
Author
Kang, Yoon-SokPark, Seong YongIto, KimihikoKubo, YoshimiShin, YongwooKim, Dong YoungSeo, Dong-HwaKim, SoojinPark, Jin-HwanDoo, Seok-GwangKoh, MeitenSeo, Jin AhPark, Kwangjin
Issue Date
2021-04
Publisher
Elsevier BV
Citation
JOURNAL OF POWER SOURCES, v.490, pp.229542
Abstract
Improving the cycling performance of Ni-rich LiNixCoyMnzO2 (NCM, 0 ≤ x,y,z < 1) is critical for commercializing rechargeable batteries based on Ni-rich NCM cathodes. Herein, we studied the structural degradation of Ni-rich NCM/graphite cylindrical 18650-type cells as a function of the cutoff voltage in the 4.2–4.4 V range by electrochemical impedance spectroscopy (EIS), scanning transmission electron microscopy–electron energy loss spectroscopy (STEM–EELS), and high-angle annular dark-field (HAADF) STEM, and modeled the Ni-rich NCM surface using density functional theory (DFT). We verified that the phase changes continuously rather than discretely from the surface into the bulk through cation mixing. Our results suggest that the thickness of the phase-change region at the surface causes the battery performance to suddenly degrade at a certain value. We found that the deterioration in cell performance is mainly due to increasing diffusion resistance in the positive electrode. A 10–25 nm cation mixing layer was observed at the cathode surface after 300 cycles, and this surface layer thickened with increasing charging voltage. Further, simulations revealed that the cathode surface spontaneously evolves oxygen at higher electrochemical potentials.
URI
https://scholarworks.unist.ac.kr/handle/201301/49979
URL
https://www.sciencedirect.com/science/article/pii/S0378775321000896
DOI
10.1016/j.jpowsour.2021.229542
ISSN
0378-7753
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ECHE_Journal Papers
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