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Seo, Dong-Hwa
Computational Energy Materials Science Lab
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  • 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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Electrochemical properties and structural evolution of O3-type layered sodium mixed transition metal oxides with trivalent nickel

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Title
Electrochemical properties and structural evolution of O3-type layered sodium mixed transition metal oxides with trivalent nickel
Author
Vassilaras, PlousiaKwon, Deok-HwangDacek, Stephen T.Shi, TanSeo, Dong-HwaCeder, GerbrandKim, Jae Chul
Issue Date
2017-03
Publisher
ROYAL SOC CHEMISTRY
Citation
JOURNAL OF MATERIALS CHEMISTRY A, v.5, no.9, pp.4596 - 4606
Abstract
The electrochemical properties of NaNi0.5Co0.5O2 and NaNi0.5Fe0.5O2 and their structural transitions as a function of Na extraction associated with redox reactions are investigated in this work. Synthesized in the O3-type layered structure, both materials show reasonable electrochemical activities at room temperature, delivering approximately 0.5 Na per formula unit at C/10 discharge. More Na can be reversibly cycled in NaNi0.5Co0.5O2 at elevated temperature and/or in an extended voltage window, while NaNi0.5Fe0.5O2 shows significant capacity fading at a high voltage cutoff which is likely due to Fe4+ migration. In situ X-ray diffraction shows that the structural changes in the two materials upon desodiation are very different. NaNi0.5Co0.5O2 goes through many different two-phase reactions including three different O3-type and three different P3-type structures during cycling, producing a voltage profile with multiple plateau-like features. In contrast, NaNi0.5Fe0.5O2 has a smooth voltage profile and shows the typical O3-P3 phase transition without lattice distortion seen in other materials. This different structural evolution upon desodiation and re-sodiation can be explained by the electronic structure of the mixed transition metals and how it perturbs the ordering between Na ions differently.
URI
https://scholarworks.unist.ac.kr/handle/201301/30522
URL
https://pubs.rsc.org/en/content/articlelanding/2017/TA/C6TA09220A#!divAbstract
DOI
10.1039/c6ta09220a
ISSN
2050-7488
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