Browsing by Author "D'Angelo, AM"
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- ItemAverage and local ordering of Yb2(Ti2-xYbx)O7-x/2 ‘stuffed’ pyrochlores: the development of a robust structural model(Elsevier, 2021-10-01) Mullens, BG; Zhang, Z; Avdeev, M; Brand, HEA; Cowie, BCC; D'Angelo, AM; Múzquiz, MS; Kennedy, BJThe long-range (average) and short-range (local) structures in the Yb2(Ti2-xYbx)O7-x/2 (x = 0.00–0.67) series were studied using a combination of diffraction and spectroscopic techniques. The average structure, established from synchrotron X-ray and neutron powder diffraction data, shows the development of multiphase regions from x = 0.134 and the formation of anti-site disorder from x = 0.335. The local structure, established from X-ray absorption near-edge structure (XANES), shows a gradual evolution of short-range disorder. The crystal field splitting energy of the Ti4+ ions decreases from 2.15 to 1.91 eV with increasing Yb3+ content, reflecting the increase in coordination number from 6 to predominantly 7. Electrochemical impedance spectroscopic studies show an increase in oxygen ionic conductivity by almost a factor of 3 upon doping with small amounts of Yb3+ (x = 0.067). These results imply that the disordering across the anion and cation sublattices are different and inducing small amounts of disorder into the pyrochlore structure may lead to applications in solid-oxide fuel cells. © 2021 Elsevier Inc.
- ItemIntroducing 4s–2p orbital hybridization to stabilize spinel oxide cathodes for lithium-ion batteries(Wiley-VCH GmbH, 2022-04-25) Liang, GM; Olsson, E; Zou, JS; Wu, ZB; Li, JX; Lu, CZ; D'Angelo, AM; Johannessen, B; Thomsen, L; Cowie, BCC; Peterson, VK; Cai, Q; Pang, WK; Guo, ZPOxides composed of an oxygen framework and interstitial cations are promising cathode materials for lithium-ion batteries. However, the instability of the oxygen framework under harsh operating conditions results in fast battery capacity decay, due to the weak orbital interactions between cations and oxygen (mainly 3d–2p interaction). Here, a robust and endurable oxygen framework is created by introducing strong 4s–2p orbital hybridization into the structure using LiNi0.5Mn1.5O4 oxide as an example. The modified oxide delivers extraordinarily stable battery performance, achieving 71.4 % capacity retention after 2000 cycles at 1 C. This work shows that an orbital-level understanding can be leveraged to engineer high structural stability of the anion oxygen framework of oxides. Moreover, the similarity of the oxygen lattice between oxide electrodes makes this approach extendable to other electrodes, with orbital-focused engineering a new avenue for the fundamental modification of battery materials. © 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH - Open access.
- ItemA robust coin-cell design for in situ synchrotron-based x-ray powder diffraction analysis of battery materials(John Wiley & Sons, Inc, 2020-10-22) Liang, GM; Hao, JN; D'Angelo, AM; Peterson, VK; Guo, ZP; Pang, WKUnderstanding structure/chemistry-function relationships of active battery materials is crucial for designing higher-performance batteries, with in situ synchrotron-based X-ray powder diffraction widely employed to gain this understanding. Such measurements cannot be performed using a conventional cell, with modifications necessary for the X-ray diffraction measurement, which unfortunately compromises battery performance and stability. Consequently, these measurements may not be representative of the typical behaviour of active materials in unmodified cells, particularly under more extreme operating conditions, such as at high voltage. Herein, we report a low-cost, simple, and robust coin-cell design enabling representative and typical cell performance during in situ X-ray powder diffraction measurements, which we demonstrate for the well-known high-voltage electrode material LiNi0.5Mn1.5O4. In addition to excellent cell stability at high voltage, the modified cell delivered an electrochemical response comparable to the standard 2032-type coin cell. This work paves an efficient way for battery researchers to perform high-quality in situ structural analysis with synchrotron X-ray radiation and will enable further insight into complex electrochemical processes in batteries. © 2020 Wiley-VCH GmbH
- ItemTotal scattering measurements at the Australian Synchrotron Powder Diffraction beamline: capabilities and limitations(International Union of Crystallography, 2023-03-01) D'Angelo, AM; Brand, HEA; Mitchell, VD; Hamilton, JL; Oldfield, DT; Liu, ACY; Gu, QFThis study describes the capabilities and limitations of carrying out total scattering experiments on the Powder Diffraction (PD) beamline at the Australian Synchrotron, ANSTO. A maximum instrument momentum transfer of 19 Å−1 can be achieved if the data are collected at 21 keV. The results detail how the pair distribution function (PDF) is affected by Qmax, absorption and counting time duration at the PD beamline, and refined structural parameters exemplify how the PDF is affected by these parameters. There are considerations when performing total scattering experiments at the PD beamline, including (1) samples need to be stable during data collection, (2) highly absorbing samples with a μR > 1 always require dilution and (3) only correlation length differences >0.35 Å may be resolved. A case study comparing the PDF atom–atom correlation lengths with EXAFS-derived radial distances of Ni and Pt nanocrystals is also presented, which shows good agreement between the two techniques. The results here can be used as a guide for researchers considering total scattering experiments at the PD beamline or similarly setup beamlines. © 2023 The Authors - Open Access CC-BY Licence 4.0
- ItemTotal scattering measurements at the Australian Synchrotron Powder Diffraction beamline: capabilities and limitations(Australian Nuclear Science and Technology Organisation, 2021-11-24) D'Angelo, AM; Gu, QF; Brand, HEA; Mitchell, VD; Hamilton, JL; Liu, ACY; Oldfield, DTThe PD beamline at the Australian Synchrotron (ANSTO) consistently receives requests to carry out total scattering experiments for various materials including battery electrodes, piezoelectrics and coordination frameworks. In this study we describe the capabilities and limitations of carrying out total scattering experiments on the Powder Diffraction beamline. A maximum instrument momentum transfer of 19 Å-1 can be achieved. Our results detail how the pair distribution function is affected by Qmax, absorption, and counting time duration at the PD beamline. We also trial a variable counting time strategy using the Mythen II detector. Refined structural parameters exemplify how the PDF is affected by these parameters. Total scattering experiments can be carried out at PD although there are limitations. These are: (1) only measurements on stable systems and at non-ambient conditions is possible if the temperature is held during data collection, (2) it is essential to dilute highly absorbing samples (μR>1), and (3) only correlation lengths >0.35 Å may be resolved. A case study comparing the PDF atom-atom correlation lengths with EXAFS derived radial distances of Ni and Pt nanoparticles is also presented, which shows good agreement between the two techniques. The results here can be used as a guide for researchers considering total scattering experiments at the PD beamline. © The Authors