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成果報告書詳細
管理番号20170000000241
タイトル*平成28年度中間年報 革新型蓄電池実用化促進基盤技術開発(国立大学法人東京大学)
公開日2017/11/14
報告書年度2016 - 2016
委託先名国立大学法人東京大学
プロジェクト番号P16001
部署名スマートコミュニティ部
和文要約
英文要約Titile:Research and Development Initiative for Scientific Innovation of New Generation Batteries2 (RISING2) (FY2016-FY2018) FY2016 Annular Report

For the development of next generation rechargeable battery materials, it is essential to find develop materials with low resistances for ionic conductivity. The main resistances for ionic conductivity are the lattice defects such as grain boundaries and heterointerfaces between electrode and electrolyte materials. In addition, point defects including vacancies or dopants also contribute to the resistance for ionic conductivity. In this project, we develop new atomic-resolution imaging techniques utilizing scanning transmission electron microscopy (STEM). Using the techniques, we will directly observe point defect structures in 3D and local electric fields formed at the interfaces in battery materials.

(1) Development of atomic-resolution 3D-STEM
To achieve high-resolution 3D imaging using TEM, several methods have been proposed including TEM tomography and confocal STEM. While, optical depth sectioning with large-angle illumination STEM is a promising technique, and therefore we have investigated the performance of LAI-STEM by using theoretical simulations [1]. To show the feasibility of LAI-STEM imaging (300 kV, 60 mrad), we demonstrate the depth location determination of a single Ce atoms in AlN as a model system for this purpose. Here, we implement the effects of both electron dose and chromatic aberration. Although the chromatic aberration gives a probe elongation along z-direction, it does not seriously retard the determination of a dopant depth location. The single atom can be visible under the low dose of 200 e-/pix, suggesting that it is possible to acquire focus-series images in beam sensitive battery materials.

(2) Differential phase contrast imaging
Owing to the structures and chemical inhomogeneity at an interface, the local charge defects (or electric field) may be introduced around the interface. This inhomogeneous local charge distribution usually suppresses the ionic conductivity across the boundary, and therefore it has been desired to develop a new methodology to observe local electric fields at interfaces. In this study, we are developing new nano-scale electric field imaging for battery materials using differential phase contrast STEM. For DPC-STEM imaging, we are using our own 16 segmented detectors, where four circular detectors are segmented into four azimuth-angle directions. We investigated the optimum condition to observe local electric fields quantitatively inside standard battery materials. Furthermore, we also develop a new light-element sensitive imaging technique [2], which could be helpful for the structure analysis of light-element containing battery materials.

[1] R. Ishikawa, S.J. Pennycook, A.R. Lupini, S.D. Findlay, N. Shibata, Y. Ikuhara, Appl. Phys. Lett. 109 163102 (2016).
[2] S.D. Findlay, R. Huang, R. Ishikawa, N. Shibata, Y. Ikuhara, Microscopy 66 3 (2017)
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