visualization of 3d compositions of lithium transition
TRANSCRIPT
Poster Presentation : PS2-09
Visualization of 3D compositions of lithium transition-metal oxides via EDS-EELS combined tomography
정채화, 양용수* (KAIST)
발표자 : 정채화[email protected]
I. Introduction 1. 연구개요
Importance of EDS & EELS tomography
For transition metal-based Li-ion battery cathode materials, accurate determination and control over the 3D distribution of different transition metals within the materials are essential.
Unlike many techniques that are either restricted to lower dimensions (2D projections or surface) or destructive (cannot detect the migration dynamics during the battery cycling), scanning transmission electron microscopy-based energy dispersive x-ray spectroscopy (STEM-EDS) tomography can provide the desired capability.
Segregation and migration of chemical elements (especially Li, Ni) can substantially affect the surface reconstruction and degradation of the cathode during the battery cycling.
I. Introduction 1. 연구개요
3D reconstruction algorithms
Miao, J., Ercius, P. & Billinge, S. J. L. Atomic electron tomography: 3D structures without crystals. Science 353, aaf2157–aaf2157 (2016).
By combining GENFIRE algorithms and EDS, EELS tomography, we expect to obtain 3D distribution of light atoms.
Ⅱ. Results 2. 결과
EDS tomography
Apply 2D Gaussian smoothing kernel
HADDFprojections
35°
-70°
70°
-35°
0°
Mn EDS projection
CoEDS projection
Ni EDS projection
OEDS projection
Sample : LiNi0.5Co0.2Mn0.3O2 Size of particles : 200 ~ 300 nm Angles Range
: [-70 °:7 °:70 °], 21 sets
Ⅱ. Results 2. 결과
3D configuration of NCM battery materials 3D STEM-EDS tomography of NCM 523 sample
100 nm
Ni:Mn:Co = 0.52:0.23:0.25
Composition of Ni, Co, Mn
Ⅱ. Results 2. 결과
EELS tomography Obtain element projections from spectrum
Sample : LiNi0.5Co0.2Mn0.3O2 Size of particles : 150 nm Angles Range : [-70 ° :60 °], 10 sets
Reference (eV)
Fitted values (eV)
Mn M edge 49 49.75, 53.45
Li k edge 55 60.1
Co M edge 60 65.75, 68.2
Ni M edge 68 Don’t exist
STEP 1. background subtraction
Fit power law : 𝐴𝐴 ∗ Energy loss1.5 + 𝐵𝐵
STEP 2. Find initial points of each peaks
Mn 2 peaks Co 2 peaksLi peak
Ⅱ. Results 2. 결과
EELS tomographySTEP 3. Obtain element image based on fitted position
HADDFprojections
Li EELS projection
Co EELS projection
Mn EELS projection
-70°
-30°
0°
35°
60°
Ⅱ. Results 2. 결과
3D configuration of NCM battery materials EELS tomography of NCM 523 sample
100 nm
ADF Li
Co Mn
Composition of Li, Co, Mn
Ⅲ. Conclusion 3. 결론
Identification of Li ions will give insight into understanding Lithium-ion transport.
Since the STEM-EDS-EELS technique is non-destructive, it can be used to track the same specimen over the course of the battery cycling, illuminating the dynamics of the migration of each chemical elements during the cycling
HAADF tomography can reveal the overall 3D morphologies and internal density, while STEM-EDS-EELS tomography shows the 3D composition map.
2021 한국현미경학회춘계학술대회