Browsing by Author "Didier, C"
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- ItemCharacterising the expression of sub-millennial scale climate events in western Europe during the early last glacial period using multi-proxy speleothem records(Australasian Quaternary Association Inc., 2022-12-06) Corrick, E; Drysdale, RN; Hellstrom, JC; Couchoud, I; Wong, HKY; Didier, C; Hai, C; Jaillet, S; Tocino, SPast abrupt climate changes act as critical analogues for understanding how the climate system may respond to future abrupt changes. One of the best examples of naturally occurring abrupt climate change is the series of millennial-scale Dansgaard-Oeschger (D-O) events that took place during the last glacial period (115,000 – 11,500 years ago). D-O events are clearly recorded in ice-cores from Greenland, with coincident climate changes detected in marine and terrestrial records spanning a range of climate zones. Greenland ice cores also record shorter-lived ‘sub-millennial’ scale events that occur within the main D-O event sequence, particularly during the early last glacial period. To what extent these sub-millennial events were expressed outside of Greenland is currently poorly understood. Here we characterise the response to sub-millennial scale climate changes in western Europe using five multi-proxy (δ18O, δ13C, Mg and Sr) speleothem records from Saint-Marcel and Orgnac Caves, France, that collectively span 127 – 87 kyr BP. The replicated speleothem records clearly preserve both millennial D-O events and sub-millennial events, demonstrating the strong coupling between the climate of south-east France and the North Atlantic across both millennial and sub-millennial timescales. Interestingly, the multiproxy record reveals a decoupling between broad temperature (indicated by δ13C) and precipitation changes (indicated by δ18O) during some of these sub-millennial scale events. This suggests that climate teleconnections operating during sub-millennial events were in some ways different to those during the stronger millennial-scale D-O events.
- ItemDirect in situ determination of the surface area and structure of deposited metallic lithium within lithium metal batteries using ultra small and small angle neutron scattering(Wiley, 2023-10-10) Didier, C; Gilbert, EP; Mata, JP; Peterson, VKDespite being the major cause of safety and performance issues in lithium metal batteries, experimental difficulties in quantifying directly the morphology of lithium deposited at electrode surfaces have meant that the mechanism of metallic lithium growth within batteries remains elusive. This study demonstrates that quantitative detail about the morphology of metallic lithium within batteries can be derived non-destructively and directly using in situ ultra-small and small-angle neutron scattering. This information is obtained over a large electrode area in cells where lithium deposition processes are typical of real-world applications. Complex variations of surface area and interfacial distances 1–10 µm and 100–300 nm are revealed in size that are influenced by current density and cell cycling history, providing valuable insight into the growth of metallic lithium features detrimental to battery performance. Such quantitative insight into the process of lithium growth is required for the development of safer high-performance lithium metal batteries. © 2023 Commonwealth of Australia. Advanced Energy Materials published by Wiley-VCH GmbH. This is an open access article under the terms of the Creative Commons Attribution License.
- ItemElucidation of the high-voltage phase in the layered sodium ion battery cathode material P3–Na0.5Ni0.25Mn0.75O2(Royal Society of Chemistry, 2020-09-30) Liu, JT; Didier, C; Sale, M; Sharma, N; Guo, ZP; Peterson, VK; Ling, CDThe P3-type layered oxide Na0.5Ni0.25Mn0.75O2 is a promising manganese-rich positive electrode (cathode) material for sodium ion batteries, with a high working voltage of 4.2–2.5 V vs. Na+/Na and a high capacity of over 130 mA h g−1 when cycled at 10 mA g−1. However, its structural evolution during battery cycling – specifically, the nature of the high-voltage phase above 4 V – has never been fully understood, which has hindered efforts to rationally modify and improve its performance. In this work we use in situ neutron diffraction to show that the phase above 4 V is a modification of the intermediate O3 phase from which all sodium has been removed, and which consequently has a dramatically shorter interlayer distance. We label this fully Na-depleted phase O3s, such that the phase evolution with increasing voltage is P3 → O3 → O3s. Having elucidated its structure, we used first-principles calculations of the electronic structure as a function of sodium content to show that reversible oxygen redox plays a key role in the electrochemical activity of this O3s phase above 4 V. We also calculated the energies of oxygen/transition metal vacancies and found that the O3s phase should be relatively stable against their formation. The results will guide future research aimed at understanding and stabilizing the O3s phase, in order to improve the performance and cycling stability of this material in sodium ion batteries. © The Royal Society of Chemistry 2020
- ItemHydrogen-containing Na3HTi1–xMnxF8 narrow-band phosphor for light-emitting diodes(American Chemical Society, 2019-01-16) Fang, MH; Yang, TH; Lesniewski, T; Lee, C; Mahlik, S; Grinberg, M; Peterson, VK; Didier, C; Pang, WK; Su, CC; Liu, RSWe synthesize the phosphor Na3HTi1–xMnxF8 (Na3HTiF8:Mn4+) material series using a coprecipitation method. We determine the complete phase and crystallographic structure of the Na3HTiF8 series end-member, including the determination of the H atoms at the 4b (0, 1/2, 0) crystallographic site within the Cmcm space group symmetry structure, resulting in a quantum efficiency of ∼44%, which is comparative to the Na2SiF6:Mn4+ phosphor materials. We successfully model the luminescent properties of the Na3HTi1–xMnxF8 material series, including temperature and time-dependent photoluminescence, providing a good prediction of the decay properties at low and high temperature and revealing the existence of Mn5+ during the ionization process. Notably, LED package data indicates that the Na3HTi1–xMnxF8 material series could be a promising candidate for high-level and back-lighting devices. This research reveals the role that hydrogen plays in determining fluoride phosphor structure and properties, revealing a new path for the synthesis of fluoride phosphors. Copyright © 2019 American Chemical Society
- ItemIn situ neutron diffraction study on layered oxides Na0.5Ni0.25Mn0.75O2(Australian Institute of Nuclear Science and Engineering (AINSE), 2020-11-11) Liu, J; Didier, C; Sale, M; Sharma, N; Guo, ZP; Peterson, VK; Ling, CDLayered oxides based on first-row transition metals dominate cathode materials for commercial batteries and remain highly interesting as well as challenging in their structural study during electrochemical reactions. Neutron diffraction is a powerful method to obtain periodic structural information complementary to that obtained by X-ray diffraction. Although inferior to X-ray diffraction in signal resolution, neutron diffraction reveals more reliable structural evolution as the whole bulk of materials are fluxed with neutron beam. Na0.5Ni0.25Mn0.75O2 is a potential sodium ion battery cathode due to its high operating voltage 3.2 V vs Na+/Na and high capacity 130 mAh/g. Its stoichiometry is designed to only utilize the redox couple Ni4+/Ni2+ to avoid the unstable redox couple Mn4+/Mn3+. The high voltage phase for this material has been under debate. The fact that sodium-containing layered oxides are highly hydroscopic, especially at low sodium content, makes it hard to study the final phase ex situ. In the work presented here, we have pushed the signal resolution of in situ neutron diffraction to the limit by loading the optimized material mass at the positive side and the corresponding amount of amorphous hard carbon at the negative side of a pouch cell. The result is the first robust proof of the reversible structural evolution from P3, O3 to O3s on charging and back to O3, P3 on discharging. © 2020 The authors.
- ItemThe influence of electrode material crystal structure on battery performance(De Gruyter, Berlin, Germany, 2021) Didier, C; Pang, WK; Peterson, VKEnergy storage demands are increasing as a result of the growing use of electric vehicles and intermittent energy sources. Lithium-ion batteries, commercialized over two decades ago, have enabled the widespread use of portable electronics, and these are being implemented both in electric vehicles and to store intermittently available energy. This type of battery operates with the so-called “rocking-chair” mechanism, where lithium ions are reversibly exchanged between two electrodes. The mechanism relies on the reversible insertion of lithium into sites within the electrode material crystal structure, with the repeated processes of lithium insertion and extraction generating atomic-level change that the bulk electrode material must accommodate. These are both the short- and long-range structural changes within electrodes that dictate, to a large degree, the performance of the whole battery. Hence, the characterization of electrode crystal structure, particularly during battery cycling, is key to understanding and improving energy storage in batteries. In this chapter, we explore the relationship between the crystal structure of electrode materials and their performance in lithium-ion batteries, with a focus on structure types that have found commercial applications. The discussion identifies what crystallographic features are useful for electrode materials and how crystal structure influences electrochemical behavior. © 2021 Walter de Gruyter GmbH, Berlin/Munich/Boston
- ItemInsight of a phase compatible surface coating for long-durable Li-rich layered oxide cathode(John Wiley & Sons, Inc, 2019-07-28) Hu, SJ; Li, Y; Chen, YH; Peng, JM; Zhou, TF; Pang, WK; Didier, C; Peterson, VK; Wang, HQ; Li, QY; Guo, ZPLi-rich layered oxides (LLOs) can deliver almost double the capacity of conventional electrode materials such as LiCoO2 and LiMn2O4; however, voltage fade and capacity degradation are major obstacles to the practical implementation of LLOs in high-energy lithium-ion batteries. Herein, hexagonal La0.8Sr0.2MnO3−y (LSM) is used as a protective and phase-compatible surface layer to stabilize the Li-rich layered Li1.2Ni0.13Co0.13Mn0.54O2 (LM) cathode material. The LSM is Mn O M bonded at the LSM/LM interface and functions by preventing the migration of metal ions in the LM associated with capacity degradation as well as enhancing the electrical transfer and ionic conductivity at the interface. The LSM-coated LM delivers an enhanced reversible capacity of 202 mAh g−1 at 1 C (260 mA g−1) with excellent cycling stability and rate capability (94% capacity retention after 200 cycles and 144 mAh g−1 at 5 C). This work demonstrates that interfacial bonding between coating and bulk material is a successful strategy for the modification of LLO electrodes for the next-generation of high-energy Li-ion batteries. © 2019 Wiley-VCH Verlag GmbH & Co.
- ItemA long cycle-life high-voltage spinel lithium-ion battery electrode achieved by site-selective doping(John Wiley & Sons, Inc, 2020-03-23) Liang, GM; Wu, ZB; Didier, C; Zhang, WC; Cuan, J; Li, BH; Ko, KY; Hung, PY; Lu, CZ; Chen, YZ; Leniec, G; Kaczmarek, SM; Johannessen, B; Thomsen, L; Peterson, VK; Pang, WK; Guo, ZPSpinel LiNi0.5Mn1.5O4 (LNMO) is a promising cathode candidate for the next-generation high energy-density lithium-ion batteries (LIBs). Unfortunately, the application of LNMO is hindered by its poor cycle stability. Now, site-selectively doped LNMO electrode is prepared with exceptional durability. In this work, Mg is selectively doped onto both tetrahedral (8a) and octahedral (16c) sites in the Fdurn:x-wiley:14337851:media:anie202001454:anie202001454-math-0001 m structure. This site-selective doping not only suppresses unfavorable two-phase reactions and stabilizes the LNMO structure against structural deformation, but also mitigates the dissolution of Mn during cycling. Mg-doped LNMOs exhibit extraordinarily stable electrochemical performance in both half-cells and prototype full-batteries with novel TiNb2O7 counter-electrodes. This work pioneers an atomic-doping engineering strategy for electrode materials that could be extended to other energy materials to create high-performance devices. © 2020 Wiley-VCH Verlag GmbH & Co
- ItemPhase evolution and intermittent disorder in electrochemically lithiated graphite determined using in operando neutron diffraction(American Chemical Society, 2020-03-24) Didier, C; Pang, WK; Guo, ZP; Schmid, S; Peterson, VKSince their commercialization in 1991, lithium-ion batteries (LIBs) have revolutionized our way of life, with LIB pioneers being awarded the 2019 Nobel Prize in Chemistry. Despite the widespread use of LIBs, many LIB applications are not realized due to performance limitations, determined largely by the ability of electrode materials to reversibly host lithium ions. Overcoming such limitations requires knowledge of the fundamental mechanism for reversible ion intercalation in electrode materials. In this work, the still-debated structure of the most common commercial electrode material, graphite, during electrochemical lithiation is revisited using in operando neutron powder diffraction of a commercial 18650 lithium-ion battery. We extract new structural information and present a comprehensive overview of the phase evolution for lithiated graphite. Charge–discharge asymmetry and structural disorder in the lithiation process are observed, particularly surrounding phase transitions, and the phase evolution is found to be kinetically influenced. Notably, we observe pronounced asymmetry over the composition range 0.5 > x > 0.2, in which the stage 2L phase forms on discharge (delithiation) but not charge (lithiation), likely as a result of the slow formation of the stage 2L phase and the closeness of the stage 2L and stage 2 phase potentials. We reconcile our measurements of this transition with a stage 2L stacking disorder model containing an intergrown stage 2 and 2L phase. We resolve debate surrounding the intercalation mechanism in the stage 3L and stage 4L phase region, observing stage-specific reflections that support a first-order phase transition over the 0.2 > x > 0.04 range, in agreement with minor changes in the slope of the stacking axis length, despite relatively unchanging 00l reflection broadening. Our data support the previously proposed /ABA/ACA/ stacking for the stage 3L phase and an /ABAB/BABA/ stacking sequence of the stage 4L phase alongside experimentally derived atomic parameters. Finally, at low lithium content 0 < x < 0.04, we find an apparently homogeneous modification of the structure during both charge and discharge. Understanding the phase evolution and mechanism of structural response of graphite to lithiation under battery working conditions through in operando measurements may provide the information needed for the development of alternative higher performance electrode materials. © 2020 American Chemical Society
- ItemPreparation of pyrite concentrate powder from the Thackaringa mine for quantitative phase analysis using x-ray diffraction(International Union of Crystallography, 2022-12) McDougall, H; Hibberd, MF; Tong, A; Neville, SM; Peterson, VK; Didier, CThe quantitative phase analysis using X-ray diffraction of pyrite ore concentrate samples extracted from the Thackaringa mine is problematic due to poor particle statistics, microabsorption and preferred orientation. The influence of sample preparation on these issues has been evaluated, with ball milling of the powder found most suitable for accurate and precise quantitative phase analysis. The milling duration and other aspects of sample preparation have been explored, resulting in accurate phase reflection intensities when particle sizes are below 5 µm. Quantitative phase analysis on those samples yielded precise phase fractions with standard deviations below 0.3 wt%. Some discrepancy between the elemental composition obtained using X-ray powder diffraction data and that determined using wavelength-dispersive X-ray fluorescence was found, and is thought to arise from unaccounted for crystalline phase substitution and the possible presence of an amorphous phase. This study provides a methodology for the precise and accurate quantitative phase analysis of X-ray powder diffraction data of pyrite ore concentrate from the Thackaringa mine and a discussion of the limitations of the method. The optimization process reveals the importance of confirming reproducibility on new samples, with as much prior knowledge as possible. © International Union of Crystallography.
- ItemSynthetic pathway determines the nonequilibrium crystallography of Li- and Mn-rich layered oxide cathode materials(American Chemical Society, 2021-02-10) Menon, AS; Ulusoy, S; Ojwang, DO; Riekehr, L; Didier, C; Peterson, VK; Salazar-Alvarez, G; Svedlindh, P; Edström, K; Gomez, CP; Brant, WRLi- 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. Copyright © 2021 The Authors. Published by American Chemical Society.
- ItemUnderstanding rechargeable battery function using in operando neutron powder diffraction(John Wiley & Sons, Inc, 2020-05-07) Liang, GM; Didier, C; Guo, ZP; Peterson, VKThe performance of rechargeable batteries is influenced by the structural and phase changes of components during cycling. Neutron powder diffraction (NPD) provides unique and useful information concerning the structure–function relation of battery components and can be used to study the changes to component phase and structure during battery cycling, known as in operando measurement studies. The development and use of NPD for in operando measurements of batteries is summarized along with detailed experimental approaches that impact the insights gained by these. A summary of the information gained concerning battery function using in operando NPD measurements is provided, including the structural and phase evolution of electrode materials and charge-carrying ion diffusion pathways through these, which are critical to the development of battery technology. © 2019 Wiley-VCH Verlag GmbH & Co.