| 1. |
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| 2. |
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| 3. |
- Klionsky, Daniel J., et al.
(författare)
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Guidelines for the use and interpretation of assays for monitoring autophagy
- 2012
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Ingår i: Autophagy. - : Informa UK Limited. - 1554-8635 .- 1554-8627. ; 8:4, s. 445-544
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Forskningsöversikt (refereegranskat)abstract
- In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process vs. those that measure flux through the autophagy pathway (i.e., the complete process); thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from stimuli that result in increased autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field.
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| 4. |
- Nguyen, Thanh N, et al.
(författare)
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Global Impact of the COVID-19 Pandemic on Stroke Volumes and Cerebrovascular Events: A 1-Year Follow-up.
- 2023
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Ingår i: Neurology. - 1526-632X. ; 100:4
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Tidskriftsartikel (refereegranskat)abstract
- Declines in stroke admission, IV thrombolysis (IVT), and mechanical thrombectomy volumes were reported during the first wave of the COVID-19 pandemic. There is a paucity of data on the longer-term effect of the pandemic on stroke volumes over the course of a year and through the second wave of the pandemic. We sought to measure the effect of the COVID-19 pandemic on the volumes of stroke admissions, intracranial hemorrhage (ICH), IVT, and mechanical thrombectomy over a 1-year period at the onset of the pandemic (March 1, 2020, to February 28, 2021) compared with the immediately preceding year (March 1, 2019, to February 29, 2020).We conducted a longitudinal retrospective study across 6 continents, 56 countries, and 275 stroke centers. We collected volume data for COVID-19 admissions and 4 stroke metrics: ischemic stroke admissions, ICH admissions, IVT treatments, and mechanical thrombectomy procedures. Diagnoses were identified by their ICD-10 codes or classifications in stroke databases.There were 148,895 stroke admissions in the 1 year immediately before compared with 138,453 admissions during the 1-year pandemic, representing a 7% decline (95% CI [95% CI 7.1-6.9]; p < 0.0001). ICH volumes declined from 29,585 to 28,156 (4.8% [5.1-4.6]; p < 0.0001) and IVT volume from 24,584 to 23,077 (6.1% [6.4-5.8]; p < 0.0001). Larger declines were observed at high-volume compared with low-volume centers (all p < 0.0001). There was no significant change in mechanical thrombectomy volumes (0.7% [0.6-0.9]; p = 0.49). Stroke was diagnosed in 1.3% [1.31-1.38] of 406,792 COVID-19 hospitalizations. SARS-CoV-2 infection was present in 2.9% ([2.82-2.97], 5,656/195,539) of all stroke hospitalizations.There was a global decline and shift to lower-volume centers of stroke admission volumes, ICH volumes, and IVT volumes during the 1st year of the COVID-19 pandemic compared with the prior year. Mechanical thrombectomy volumes were preserved. These results suggest preservation in the stroke care of higher severity of disease through the first pandemic year.This study is registered under NCT04934020.
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| 5. |
- Chang, Ribooga, et al.
(författare)
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Deciphering the existence of hexagonal sodium zirconate CO2 sorbent
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Sodium zirconate (sodium zirconium oxide; Na2ZrO3) is amongst the most investigated carbon dioxide (CO2) sorbent. Na2ZrO3 is renowned for its high capture capacity and cyclic stability. It can effectively capture CO2 at temperatures that are found in industrial processes such as the manufacture of steel or cement. Na2ZrO3 is reported to adopt monoclinic, hexagonal, and cubic structures since it was first discussed in the 1960s. Researchers relied on the differences in the relative intensities between two peaks (2θ ~ 16.2 and 38.7 °) in the powder X-ray diffraction (PXRD) pattern to determine the phase of this compound. It is also widely believed that the CO2 capture performance of Na2ZrO3 is related to the crystal structure, yet the crystal structure of hexagonal Na2ZrO3 has remained elusive. With the use of 3D electron diffraction (3D ED), X-ray photoelectron spectroscopy (XPS), and PXRD, we show that the hexagonal Na2ZrO3 does not exist. The so-called hexagonal Na2ZrO3 is Na2ZrO3 with three different types of disorder. Furthermore, the two PXRD peaks (2θ ~ 16.2 and 38.7 °) cannot be used to distinguish the different phases of Na2ZrO3, as the changes in the PXRD pattern are related to the extent of structure disorder. Finally, we also show that the CO2 capture properties of Na2ZrO3 are related to the Na+ site occupancy between different Na2ZrO3 samples, and not differences in crystal structures. The findings from our work shows that the current literature discussion on the structure of Na2ZrO3 is misleading. In order to further develop Na2ZrO3 as well as other mixed-metal oxides for applications, their structures, as well as any disorder, needs be understood using the methods shown in this study.
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| 6. |
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| 7. |
- Chien, Yu-Chuan, et al.
(författare)
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Development of operando XRD coin cells for lithium-sulfur batteries
- 2018
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Lithium-sulfur (Li-S) batteries has been regarded as one of the promising technology for the next generation of rechargeable batteries due to its high theoretical energy density (2600 Wh/kg [1]). Several works [2–7] on operando X-ray diffraction (XRD) of the Li-S system have been published; however, their experimental setups showed one or more of the following drawbacks. First, the amount of electrolyte was often not reported or would be considered too high for a common Li-S cell, which has been demonstrated to have a significant impact on the behavior of the system [8]. Another issue is the non-uniform stack pressure and electron conductivity of the operando cell setup, whose effects were found by both experiments and simulations [9].This work aims to tackle with the above-mentioned issues by modifying commercial coin cells and using X-ray transparent metal, beryllium, as the spacers. By doing so, the electron conductivity and stack pressure can be expected to be uniform throughout the electrodes. The amount of electrolyte can also be precisely controlled since no vacuum-sealing is required for coin cells. A preliminary diffraction pattern obtained with the cell setup can be seen in Fig. 1. With electrochemical properties similar to common Li-S cells, ‘online’ electrochemical characterization techniques, e.g. Intermittent Current Interruption (ICI) method for following cell resistance [10], will be applicable with operando XRD, revealing more information about this complex system.Figure 1 XRD patterns of alpha-S and electrode material in the modified coin cell.References[1] J. Tan, et al., Nanoscale (2017) 19001–19016.[2] J. Nelson, et al., J. Am. Chem. Soc. 134 (2012) 6337–6343.[3] N.A. Cañas, et al., J. Power Sources 226 (2013) 313–319.[4] S. Waluś, et al., Chem. Commun. 49 (2013) 7899.[5] M. a. Lowe, et al., RSC Adv. 4 (2014) 18347.[6] J. Kulisch, et al., Phys. Chem. Chem. Phys. 16 (2014) 18765–18771.[7] J. Conder, et al., Nat. Energy 2 (2017) 1–7.[8] M.J. Lacey, ChemElectroChem (2017) 1–9.[9] O.J. Borkiewicz, et al., J. Phys. Chem. Lett. 6 (2015) 2081–2085.[10] M.J. Lacey, et al., Chem. Commun. 51 (2015) 16502–16505.
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| 8. |
- Chien, Yu-Chuan, 1990-, et al.
(författare)
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Rapid determination of solid-state diffusion coefficients in Li-based batteries via intermittent current interruption method
- 2023
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Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- The galvanostatic intermittent titration technique (GITT) is considered the go-to method for determining the Li+ diffusion coefficients in insertion electrode materials. However, GITT-based methods are either time-consuming, prone to analysis pitfalls or require sophisticated interpretation models. Here, we propose the intermittent current interruption (ICI) method as a reliable, accurate and faster alternative to GITT-based methods. Using Fick’s laws, we prove that the ICI method renders the same information as the GITT within a certain duration of time since the current interruption. Via experimental measurements, we also demonstrate that the results from ICI and GITT methods match where the assumption of semi-infinite diffusion applies. Moreover, the benefit of the non-disruptive ICI method to operando materials characterization is exhibited by correlating the continuously monitored diffusion coefficient of Li+ in a LiNi0.8Mn0.1Co0.1O2-based electrode to its structural changes captured by operando X-ray diffraction measurements.
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| 9. |
- Chien, Yu-Chuan, 1990-, et al.
(författare)
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Simultaneous Monitoring of Crystalline Active Materials and Resistance Evolution in Lithium-Sulfur Batteries
- 2020
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Ingår i: Journal of the American Chemical Society. - : AMER CHEMICAL SOC. - 0002-7863 .- 1520-5126. ; 142:3, s. 1449-1456
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Tidskriftsartikel (refereegranskat)abstract
- Operando X-ray diffraction (XRD) is a valuable tool for studying secondary battery materials as it allows for the direct correlation of electrochemical behavior with structural changes of crystalline active materials. This is especially true for the lithium-sulfur chemistry, in which energy storage capability depends on the complex growth and dissolution kinetics of lithium sulfide (Li2S) and sulfur (S-8) during discharge and charge, respectively. In this work, we present a novel development of this method through combining operando XRD with simultaneous and continuous resistance measurement using an intermittent current interruption (ICI) method. We show that a coefficient of diffusion resistance, which reflects the transport properties in the sulfur/carbon composite electrode, can be determined from analysis of each current interruption. Its relationship to the established Warburg impedance model is validated theoretically and experimentally. We also demonstrate for an optimized electrode formulation and cell construction that the diffusion resistance increases sharply at the discharge end point, which is consistent with the blocking of pores in the carbon host matrix. The combination of XRD with ICI allows for a direct correlation of structural changes with not only electrochemical properties but also energy loss processes at a nonequilibrium state and, therefore, is a valuable technique for the study of a wide range of energy storage chemistries.
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| 10. |
- Chien, Yu-Chuan, 1990-, et al.
(författare)
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Understanding the Impact of Precipitation Kinetics on the Electrochemical Performance of Lithium–Sulfur Batteries by Operando X-ray Diffraction
- 2022
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 126:6, s. 2971-2979
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Tidskriftsartikel (refereegranskat)abstract
- The complex reaction mechanism of the lithium–sulfur battery system consists of re-petitive dissolution and precipitation of the sulfur-containing species in the positiveelectrode. In particular, the precipitation of lithium sulfide (Li2S) during discharge hasbeen considered a crucial factor for achieving a high degree of active material utiliza-tion. Here, the influence of electrolyte amount, electrode thickness, applied current andelectrolyte salt on the formation of Li2S is systematically investigated in a series ofoperando X-ray diffraction experiments. Through a combination of simultaneous dif-fraction and resistance measurements, the evolution of the intensity from Li2S is di-rectly correlated to the variation in internal resistance and transport properties insidethe positive electrode. The correlation indicates that at different stages, the Li2S precip-itation both facilitates and impedes the discharge process. The kinetic information ofLi2S formation offers mechanistic explanations for the strong impact of different elec-trochemical cell parameters on the performance and thus, directions for holistic optimi-zations to achieve high sulfur utilization.
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| 11. |
- Fritze, Stefan, et al.
(författare)
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Magnetron sputtering of carbon supersaturated tungsten films-A chemical approach to increase strength
- 2021
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Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 208
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Tidskriftsartikel (refereegranskat)abstract
- Tungsten (W)-based materials attract significant attention due to their superior mechanical properties. Here, we present a chemical approach based on the addition of carbon (C) for increased strength via the combination of three strengthening mechanisms in W thin films. W:C thin films with C concentrations up to-4 at.% were deposited by magnetron sputtering. All films exhibit a body-centred-cubic structure with strong texture and columnar growth behaviour. X-ray and electron diffraction measurements suggest the formation of supersaturated W:C solid solution phases. The addition of C reduced the average column width from-133 nm for W to-20 nm for the film containing-4 at.% C. The column refinement is explained by a mechanism where C acts as re-nucleation sites. The W film is-13 GPa hard, while the W:C films achieve a peak hardness of-24 GPa. The W:C films are-11 GPa harder than the W film, which is explained by a combination of grain refinement strengthening, solid solution strengthening and increased dislocation density. Additional micropillar compression tests showed that the flow stress increased upon C addition, from-3.8 to-8.3 GPa and no brittle fracture was observed.
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| 12. |
- Menon, Ashok S., et al.
(författare)
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A Crystallographic Reinvestigation of Li1.2Mn0.6Ni0.2O2
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Despite substantial research interest, the crystallography of the promising Li-ion positive electrode material, Li1.2Mn0.6Ni0.2O2, remains disputed. The dispute is predicated on the description of the cationic arrangement in the structure, and multiple structure models have been proposed. This study attempts to provide a fresh perspective to this debate through a multi-scalar structural characterisation of Li1.2Mn0.6Ni0.2O2. Combining Bragg diffraction, transmission electron microscopy and magnetic measurements with reverse Monte Carlo analysis of total scattering data, a quantitative structural description of Li1.2Mn0.6Ni0.2O2 is developed and the existing single- and multi-phase structural descriptions of this compound have been unified. Furthermore, the merits and drawbacks of each technique is evaluated with respect to the crystallography of Li1.2Mn0.6Ni0.2O2 to explain the factors that have contributed to the lack of clarity pervading the structural description of this material. It is envisioned that a better understanding of the crystallography of Li1.2Mn0.6Ni0.2O2 contributes to harnessing the electrochemical potential of this compound.
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| 13. |
- Menon, Ashok S., et al.
(författare)
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Influence of Synthesis Routes on the Crystallography, Morphology, and Electrochemistry of Li2MnO3
- 2020
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 12:5, s. 5939-5950
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Tidskriftsartikel (refereegranskat)abstract
- With the potential of delivering reversible capacities of up to 300 mAh/g, Li-rich transition-metal oxides hold great promise as cathode materials for future Li-ion batteries. However, a cohesive synthesis-structure-electrochemistry relationship is still lacking for these materials, which impedes progress in the field. This work investigates how and why different synthesis routes, specifically solid-state and modified Pechini sol-gel methods, affect the properties of Li2MnO3, a compositionally simple member of this material system. Through a comprehensive investigation of the synthesis mechanism along with crystallographic, morphological, and electrochemical characterization, the effects of different synthesis routes were found to predominantly influence the degree of stacking faults and particle morphology. That is, the modified Pechini method produced isotropic spherical particles with approximately 57% faulting and the solid-state samples possessed heterogeneous morphology with approximately 43% faulting probability. Inevitably, these differences lead to variations in electrochemical performance. This study accentuates the importance of understanding how synthesis affects the electrochemistry of these materials, which is critical considering the crystallographic and electrochemical complexities of the class of materials more generally. The methodology employed here is extendable to studying synthesis-property relationships of other compositionally complex Li-rich layered oxide systems.
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| 14. |
- Menon, Ashok S., et al.
(författare)
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Synthesis-structure relationships in Li- and Mn-rich layered oxides : phase evolution, superstructure ordering and stacking faults
- 2022
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry. - 1477-9226 .- 1477-9234. ; 51:11, s. 4435-4446
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Tidskriftsartikel (refereegranskat)abstract
- Li- and Mn-rich layered oxides are promising positive electrode materials for future Li-ion batteries. The presence of crystallographic features such as cation-mixing and stacking faults in these compounds make them highly susceptible to synthesis-induced structural changes. Consequently, significant variations exist in the reported structure of these compounds that complicate the understanding of how the crystallographic structure influences its properties. This work investigates the synthesis-structure relations for three widely investigated Li- and Mn-rich layered oxides: Li2MnO3, Li1.2Mn0.6Ni0.2O2 and Li1.2Mn0.54Ni0.13Co0.13O2. For each compound, the average structure is compared between two synthetic routes of differing degrees of precursor mixing and four annealing protocols. Furthermore, thermodynamic and synthesis-specific kinetic factors governing the equilibrium crystallography of each composition are considered. It was found that the structures of these compounds are thermodynamically metastable under the synthesis conditions employed. In addition to a driving force to reduce stacking faults in the structure, these compositions also exhibited a tendency to undergo structural transformations to more stable phases under more intense annealing conditions. Increasing the compositional complexity introduced a kinetic barrier to structural ordering, making Li1.2Mn0.6Ni0.2O2 and Li1.2Mn0.54Ni0.13Co0.13O2 generally more faulted relative to Li2MnO3. Additionally, domains with different degrees of faulting were found to co-exist in the compounds. This study offers insight into the highly synthesis-dependent subtle structural complexities present in these compounds and complements the substantial efforts that have been undertaken to understand and optimise its electrochemical properties.
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| 15. |
- Menon, Ashok S.
(författare)
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Synthesis–Structure–Property Relationships in Li- and Mn-rich Layered Oxides
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The commercialisation of Li-ion batteries over the last decade has provided additional impetus for the improvement of existing energy storage technologies. Towards this, a major portion of the global efforts includes exploratory research aimed at the development of new material chemistries. Aligning with this theme, this Thesis explores the synthesis–structure–property relationships in Li- and Mn-rich layered oxides, a cost-effective high-capacity material system that shows promise as a positive electrode material for future Li-ion batteries. The compositional and crystallographic diversity of Li- and Mn-rich layered oxides make them particularly susceptible to synthesis-dependent variations and exacerbates structural characterisation. Therefore, understanding how synthetic variations influence their structural and electrochemical properties is a crucial step in realising their potential as positive electrode materials.Even for simple compositions like Li2MnO3, dissimilar crystallographic ordering and particle morphologies are produced depending on whether a solid-state or sol-gel synthesis approach was implemented. Subsequently, due to the higher degree of structural disorder and larger surface area, the sol-gel sample exhibited higher initial electrochemical capacities. The structural features present in these compounds such as cation site-mixing and stacking faults, manifest over varying crystallographic regimes. Hence, complementary characterisation techniques that probe different structural length scales are necessary for an accurate structural characterisation of these compounds. This factor, together with their complex crystallography, have led to contradictory single- and multi-phase structure models being reported for complex Li- and Mn-rich layered oxides. By using a combination of diffraction, spectroscopic techniques and magnetic measurements it was discovered that Li1.2Mn0.54Ni0.13Co0.13O2 can exist in both single- and multi-phase structural forms if synthesised through sol-gel and solid-state methods, respectively. Further studies following the same theme revealed that when synthesised under common laboratory conditions these compounds are metastable. Here, the composition and synthesis play a critical role in the thermodynamic and kinetic factors affecting the resultant phase, domain structure and degree of cationic order. Finally, to encompass all the structural features contained in Li- and Mn-rich layered oxides, a supercell-based structure model for Li- and Mn-rich layered oxides, using Li1.2Mn0.6Ni0.2O2 as an example, is presented. Summing all the work together from the thesis, a critical evaluation of commonly used characterisation techniques is also provided as a guideline for future research in this field.
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| 16. |
- Menon, Ashok S., et al.
(författare)
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Synthetic Pathway Determines the Nonequilibrium Crystallography of Li- and Mn-Rich Layered Oxide Cathode Materials
- 2021
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Ingår i: ACS Applied Energy Materials. - : American Chemical Society (ACS). - 2574-0962. ; 4:2, s. 1924-1935
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Tidskriftsartikel (refereegranskat)abstract
- Li- and Mn-rich layered oxides show significant promise as electrode materials for future Li-ion batteries. However, an accurate description of its crystallography remains elusive, with both single-phase solid solution and multiphase structures being proposed for high performing materials such as Li1.2Mn0.54Ni0.13Co0.13O2. Herein, we report the synthesis of single- and multiphase variants of this material through sol-gel and solid-state methods, respectively, and demonstrate that its crystallography is a direct consequence of the synthetic route and not necessarily an inherent property of the composition, as previously argued. This was accomplished via complementary techniques that probe the bulk and local structure followed by in situ methods to map the synthetic progression. As the electrochemical performance and anionic redox behavior are often rationalized on the basis of the presumed crystal structure, clarifying the structural ambiguities is an important step toward harnessing its potential as an electrode material.
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| 17. |
- Naylor, Andrew J., et al.
(författare)
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Depth-dependent oxygen redox activity in lithium-rich layered oxide cathodes
- 2019
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry. - 2050-7488. ; 7:44, s. 25355-25368
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Tidskriftsartikel (refereegranskat)abstract
- Lithium-rich materials, such as Li1.2Ni0.2Mn0.6O2, exhibit capacities not limited by transition metal redox, through the reversible oxidation of oxide anions. Here we offer detailed insight into the degree of oxygen redox as a function of depth within the material as it is charged and cycled. Energy-tuned photoelectron spectroscopy is used as a powerful, yet highly sensitive technique to probe electronic states of oxygen and transition metals from the top few nanometers at the near-surface through to the bulk of the particles. Two discrete oxygen species are identified, On− and O2−, where n < 2, confirming our previous model that oxidation generates localised hole states on O upon charging. This is in contrast to the oxygen redox inactive high voltage spinel LiNi0.5Mn1.5O4, for which no On− species is detected. The depth profile results demonstrate a concentration gradient exists for On− from the surface through to the bulk, indicating a preferential surface oxidation of the layered oxide particles. This is highly consistent with the already well-established core–shell model for such materials. Ab initio calculations reaffirm the electronic structure differences observed experimentally between the surface and bulk, while modelling of delithiated structures shows good agreement between experimental and calculated binding energies for On−.
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| 18. |
- Ojwang, Dickson O., et al.
(författare)
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Moisture-Driven Degradation Pathways in Prussian White Cathode Material for Sodium-Ion Batteries
- 2021
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 13:8, s. 10054-10063
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Tidskriftsartikel (refereegranskat)abstract
- The high-theoretical-capacity (∼170 mAh/g) Prussian white (PW), NaxFe[Fe(CN)6]y·nH2O, is one of the most promising candidates for Na-ion batteries on the cusp of commercialization. However, it has limitations such as high variability of reported stable practical capacity and cycling stability. A key factor that has been identified to affect the performance of PW is water content in the structure. However, the impact of airborne moisture exposure on the electrochemical performance of PW and the chemical mechanisms leading to performance decay have not yet been explored. Herein, we for the first time systematically studied the influence of humidity on the structural and electrochemical properties of monoclinic hydrated (M-PW) and rhombohedral dehydrated (R-PW) Prussian white. It is identified that moisture-driven capacity fading proceeds via two steps, first by sodium from the bulk material reacting with moisture at the surface to form sodium hydroxide and partial oxidation of Fe2+ to Fe3+. The sodium hydroxide creates a basic environment at the surface of the PW particles, leading to decomposition to Na4[Fe(CN)6] and iron oxides. Although the first process leads to loss of capacity, which can be reversed, the second stage of degradation is irreversible. Over time, both processes lead to the formation of a passivating surface layer, which prevents both reversible and irreversible capacity losses. This study thus presents a significant step toward understanding the large performance variations presented in the literature for PW. From this study, strategies aimed at limiting moisture-driven degradation can be designed and their efficacy assessed.
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| 19. |
- S. Menon, Ashok, et al.
(författare)
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Synthesis–Structure Relationships in Li- and Mn-rich Layered Oxides
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Li- and Mn-rich layered oxides are promising positive electrode materials for future Li-ion batteries. The coexistence of complex crystallographic features like cation-mixing and stacking faults make them highly susceptible to synthesis-induced crystallographic changes. Consequently, this has resulted in significant variations in the reported structure of these materials and exacerbated the difficulty in understanding the crystallography of these materials. Here, the effect of synthesis methods and annealing parameters on the average structure of three Li- and Mn-rich layered oxides—Li2MnO3, Li1.2Mn0.6Ni0.2O2 and Li1.2Mn0.54Ni0.13Co0.13O2—have been systematically investigated. Each compound is synthesized through two methods using four annealing protocols and the resultant structural changes are studied, to improve our understanding of the synthesis–structure relationships in these materials. Furthermore, synthesis-specific thermodynamic and kinetic factors governing the equilibrium crystallography of each composition are also explored. Improving our understanding of how the synthesis affects the pristine structure of these materials is an important step in developing these material systems for use as future positive electrode materials.
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| 20. |
- Tunes, Matheus A., et al.
(författare)
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From high-entropy alloys to high-entropy ceramics : The radiation-resistant highly concentrated refractory carbide (CrNbTaTiW)C
- 2023
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Ingår i: Acta Materialia. - : Elsevier. - 1359-6454 .- 1873-2453. ; 250
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Tidskriftsartikel (refereegranskat)abstract
- High-entropy materials represent the state-of-the-art on the alloy design strategy for future applications in extreme environments. Recent data indicates that high-entropy alloys (HEAs) exhibit outstanding radiation resistance in face of existing diluted alloy counterparts due to suppressed damage formation and evolution. An extension of the HEA concept is presented in this paper towards the synthesis and characterization of novel high-entropy ceramics as emergent materials for application in environments where energetic particle irradiation is a major concern. A novel carbide within the quinary refractory system CrNbTaTiW has been synthesized using magnetron-sputtering. The material exhibited nanocrystalline grains, single-phase crystal structure and C content around 50 at.%. Heavy-ion irradiation with in-situ Transmission Electron Microscopy was used to assess the irradiation response of the new high-entropy carbide (HEC) at 573 K and a comparison with the HEA within the system is made. No displacement damage effects appear within the microstructures of both HEA and HEC up to a dose of 10 displacements-per-atom. Surprisingly, the HEC has not amorphized under the investigated conditions. Xe was implanted in both materials and bubbles nucleated, but smaller sizes compared with conventional nuclear materials shedding light they are potential candidates for use in nuclear energy.
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