| 1. |
- Mikheenkova, Anastasiia, et al.
(author)
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Visualizing ageing-induced heterogeneity within large prismatic lithium-ion batteries for electric cars using diffraction radiography
- 2024
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In: Journal of Power Sources. - : Elsevier BV. - 0378-7753 .- 1873-2755. ; 599
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Journal article (peer-reviewed)abstract
- In this study, Synchrotron X-ray diffraction (XRD) radiography was utilized to investigate the ageing heterogeneity in 48 Ah prismatic lithium-ion cells with Ni-rich LiNi0.8Mn0.1Co0.1O2 (NMC811) as the positive electrode active material and graphite as the negative electrode active material after ∼2800 cycles. The study revealed that the area closest to the positive electrode tab is most vulnerable to degradation, particularly impacting the NMC material. Application of principal component analysis allowed to differentiate and visualize part of positive electrode material that has a different degradation due to the lithium plating. A comparison of non-destructive X-ray diffraction-based methods and electrochemical characterization method which was performed on the opened cell has shown an importance of a complementary approach. Our results highlight the feasibility of employing non-destructive techniques to study large prismatic cells, thereby presenting extensive opportunities for advancements in battery research and industry.
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| 2. |
- Gustafsson, Olof, et al.
(author)
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Design and Operation of an Operando Synchrotron Diffraction Cell Enabling Fast Cycling of Battery Materials
- 2021
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In: Batteries & Supercaps. - : John Wiley & Sons. - 2566-6223. ; 4:10, s. 1599-1604
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Journal article (peer-reviewed)abstract
- Operation of a battery typically involves dynamic and non-equilibrium processes, making real time operando techniques crucial for understanding their nature. Operando X-ray diffraction is an important technique for investigating metastable intermediates and non-equilibrium phase transitions in crystalline electrode materials. Currently employed experimental setups often apply a disruptive approach to cell design, whereby the integrity of standard electrochemical cells is compromised to facilitate collection of high-quality diffraction data. Here, we present a non-disruptive approach to adapting the use of a standard pouch cell that enables fast and long-term cell cycling. Suitability of the setup is demonstrated on the well-studied cathode material LiNi0.5Mn1.5O4. While exhibiting comparable electrochemical behavior to a standard pouch cell up to a current rate of 8 C (∼6.6 mA cm−2), phase transitions could be monitored accurately. Thus, the cell provides a new alternative to investigating non-equilibrium transitions and long-term aging effects in battery materials.
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| 3. |
- Gustafsson, Olof, 1992-, et al.
(author)
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Mind the miscibility gap : Cation mixing and current density driven non-equilibrium phase transformations in spinel cathode materials
- 2022
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In: Frontiers in Energy Research. - : Frontiers Media S.A.. - 2296-598X. ; 10
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Journal article (peer-reviewed)abstract
- Cathode materials that exhibit phase transitions with large structural rearrangements during electrochemical cycling are generally seen as disadvantageous. Large volume changes and lattice mismatches between intermediate phases tend to lead to significant kinetic barriers, as well as strain and particle cracking. In this regard, solid solution reactions are more desirable as they provide lower energy barriers and no miscibility gap between co-existing phases. The high-voltage cathode material LiNi0.5Mn1.5O4 is an interesting candidate for high power and rate capability applications, however little is known on how its phase transitions occur on the particle level. In the presented work operando X-ray diffraction was utilized together with detailed peak profile analysis to elucidate the phase transition mechanism dependency on transition metal cation order and current density. When fully disordered, the material was found to undergo a bulk single-phase solid solution reaction between the intermediate phases LiNi0.44Mn1.56O4 and Li0.5Ni0.44Mn1.56O4 followed by a first order phase transition with a coherent interphase between the intermediates Li0.5Ni0.44Mn1.56O4 and Ni0.44Mn1.6O4. When fully ordered and slightly less ordered, two separate first order phase transitions with a coherent interphase between the same intermediate phases were observed. On discharge, the fast kinetics of the transition between Li0.5Ni0.44Mn1.56O4 and LiNi0.44Mn1.56O4 resulted in less strain on the former phase. For all samples the miscibility gap between the intermediate phases narrowed with increased current density, suggesting that the solid solution domain formed at the coherent interphase can be extended when the rate of (de)lithiation exceeds the movement speed of the interphase at the phase transition. This effect was found to be larger with increasing cation disorder. The influence of transition metal ordering on the ability to form solid solutions is in good agreement with computational phase diagrams of LiNi0.5Mn1.5O4, showing that disorder is important for promoting and stabilizing solid solutions. These results indicate that the degree of transition metal ordering within the material is of importance for obtaining a material with small lattice mismatches between the involved intermediate phases and for rational design of full solid solution materials.
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| 4. |
- Holzapfel, Damian M., et al.
(author)
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Influence of ion irradiation-induced defects on phase formation and thermal stability of Ti0.27Al0.21N0.52 coatings
- 2022
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In: Acta Materialia. - : Elsevier. - 1359-6454 .- 1873-2453. ; 237
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Journal article (peer-reviewed)abstract
- The influence of changes induced by ion irradiation on structure and thermal stability of metastable cubic (Ti,Al)N coatings deposited by cathodic arc evaporation is systematically investigated by correlating experiments and theory. Decreasing the nitrogen deposition pressure from 5.0 to 0.5 Pa results in an ion flux-enhancement by a factor of three and an increase of the average ion energy from 15 to 30 eV, causing the stress-free lattice parameter to expand from 4.170 to 4.206 Å, while the chemical composition of Ti0.27Al0.21N0.52 remains unchanged. The 0.9% lattice parameter increase is a consequence of formation of Frenkel pairs induced by ion bombardment, as revealed by density functional theory (DFT) simulations. The influence of the presence of Frenkel pairs on the thermal stability of metastable Ti0.27Al0.21N0.52 is investigated by scanning transmission electron microscopy, differential scanning calorimetry, atom probe tomography and in-situ synchrotron X-ray powder diffraction. It is demonstrated that the ion flux and ion energy induced formation of Frenkel pairs increases the thermal stability as the Al diffusion enabled crystallization of the wurtzite solid solution is retarded. This can be rationalized by DFT predictions since the presence of Frenkel pairs increases the activation energy for Al diffusion by up to 142%. Hence, the thermal stability enhancement is caused by a hitherto unreported mechanism - the Frenkel pair impeded Al mobility and thereby retarded formation of wurtzite solid solution.
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| 5. |
- Sørensen, Daniel Risskov, et al.
(author)
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Methods-Spatially Resolved Diffraction Study of the Uniformity of a Li-Ion Pouch Cell
- 2022
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In: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 169:3
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Journal article (peer-reviewed)abstract
- A lab-made, multilayered Li-ion battery pouch cell is investigated using in-operando neutron powder diffraction (NPD) and spatially resolved powder X-ray diffraction (SR-PXRD) with the aim of investigating how to compare the information obtained from the two complementary techniques on a cell type with a complicated geometry for diffraction. The work focusses on the anode and cathode lithiation as obtained from the LiC6/LiC12 weight ratio and the NMC111 c/a-ratio, respectively. Neutron powder diffractograms of a sufficient quality for Rietveld refinement are measured using a rotation stage to minimize geometrical effects. Using SR-PXRD, the cell is shown to be non-uniform in its anode and cathode lithiation, with the edges of the cell being less lithiated/delithiated than the center in the fully charged state. The non-uniformity is more pronounced for high charging current than low charging current. The averaged SR-PXRD data is found to match the bulk NPD data well. This is encouraging as it seems to allow comparisons between studies using either of these complementary techniques. This work will also serve as a benchmark for our future studies on pouch cells with novel non-commercial cathode and/or anode materials.
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