Browsing by Author "Yang, J"

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    Ab initio thermodynamic optimization of Ni-rich Ni–Co–Mn oxide cathode coatings
    (Elsevier, 2020-02-29) Liu, B; Liu, JH; Yang, J; Wang, D; Ye, CC; Wang, DY; Avdeev, M; Shi, S; Yang, JH; Zhang, WQ
    The effectiveness of surface coatings in improving the stability and cycling performance of cathodes has been demonstrated since they are first proposed in the 1990's. However, the progress since then is made mostly using the trial-and-error method. Herein, an automated electrochemical-chemical stability design scheme based on first-principles thermodynamics calculations of reaction models is presented to optimize coatings for Ni-rich nickel–cobalt–manganese oxide (NCM) cathodes. Given that the coating must possess a wider electrochemical window than the cathode without the occurrence of Li-ion redistribution at the cathode/coating interface, the reaction energies of both lithium insertion/extraction and decomposition process associated with the coating are used as one of the two screening criteria. As the coating is also required to be chemically stable in Li residues and hydrofluoric-acid containing liquid environment, the positive reaction energy achieved by adjusting molar ratio of the components is used as another criterion. Using these two screening criteria, we demonstrate that lithium-containing metal phosphates, rather than previously suggested Li-containing metal oxides, are the optimal coatings for Ni-rich NCM cathodes, which is confirmed experimentally. The proposed approach is general and can be used to find optimal coating materials for any other cathodes. © 2020 Elsevier B.V.
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    Controlling spin orientation and metamagnetic transitions in anisotropic van der Waals antiferromagnet CrPS4 by hydrostatic pressure
    (Wiley, 2022-02) Peng, Y; Lin, Z; Tian, G; Yang, J; Zhang, P; Wang, F; Gu, P; Liu, X; Wang, CW; Avdeev, M; Liu, F; Zhou, D; Han, R; Shen, P; Yang, W; Liu, S; Ye, Y; Yang, J
    Controlling the phases of matter is a central task in condensed matter physics and materials science. In 2D magnets, manipulating spin orientation is of great significance in the context of the Mermin–Wagner theorem. Herein, a systematic study of temperature‐ and pressure‐dependent magnetic properties up to 1 GPa in van der Waals CrPS4 is reported. Owing to the temperature‐dependent change of the magnetic anisotropy energy, the material undergoes a first‐order spin reorientation transition with magnetic moments realigning from being almost parallel with the c axis in the ac plane to the quasi‐1D chains of CrS6 octahedra along the b axis upon heating. The spin reorientation temperature is suppressed after applying pressure, shifting the high‐temperature phase to lower temperatures with the emergence of spin‐flop transitions under magnetic fields applied along the b axis. The saturation field increases with pressure, indicating the enhancement of interlayer antiferromagnetic coupling. However, the Néel temperature is slightly reduced, which is ascribed to the suppression of intralayer ferromagnetic coupling. The work demonstrates the control of spin orientation and metamagnetic transitions in layered antiferromagnets, which may provide new perspectives for exploring 2D magnetism and related spintronic devices. © 2021 Wiley-VCH GmbH.
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    Fabrication of sub-stoichiometric Ti2O3 for room temperature thermoelectric energy regeneration: tuning of structural and electronic properties via defects engineering
    (Australian Institute of Nuclear Science and Engineering (AINSE), 2018-11-19) Yang, J; Liu, Y; Yu, DH; Li, S
    Titanium oxides has drawn extensive attention as functional electronic materials in the past few years, due to their unique layered structure and physical properties. Sub-stoichiometric titania are particularly interesting non-toxic materials for thermoelectric applications because of their high electrical conductivity with possible low phonon thermal conductivities originated from phonon scatterings at ordered defect planes. Hereby, layered sub-stoichiometric Ti2O3 material has been successfully fabricated by densifications of the ball-milled precursors with spark plasma sinterings. The experiments were performed on densified Ti2O3 samples with 0.5, 3 and 10 h ball-milling times to compare the changes in PDOS. The application of high-energy ball milling could significantly de crease the grain size in the SPS-densified bulk sample, and thus affect the phonon behaviours. The XRD results showed with the increasing of ball milling hours, the percentage of Ti3O5 increased while Ti2O3 is still the main phase. Measurements of phonon density-of-states (PDOS) were per formed with the PELICAN time-of-flight neutron spectrometer in the energy-gain mode at ANSTO, at 200, 300, 500 and 650 K, respectively. The overall shapes of the GDOS are very similar across the three samples, with three peaks located at around 20, 40, and 60 meV and matched well with the calculated PDOS of Ti2O3, indicating the dominate phase for three samples are still Ti2O3. With the temperature increasing, the peak intensity at around ~20 meV increased, however, the red-shifts and intensity decreases were observed at the 40 and 60 meV phonon DOS peaks (as indication of anharmonic effects). This suggested that the acoustic phonons response differently to temperature increase compared to optical phonons. The intensities at between 50 to 60 meV increases for the 10H spectrum, compared to the other two. This is probably because of the excitation of the phonon states in Ti3O5, as the increased Ti3O5 percentage in 10H sample. Our results suggested the measurement matched well with the theoretical study, which indicates the structural changes could have played significant roles in determining the phononic structure of sub-stoichiometric Ti2O3 based material. © The Authors.
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    Fluorine substitution in magnesium hydride as a tool for thermodynamic control
    (American Chemical Society, 2020-04-01) Humphries, TD; Yang, J; Mole, RA; Paskevicius, M; Bird, JE; Rowles, MR; Tortoza, MS; Sofianos, MV; Yu, DH; Buckley, CE
    Metal hydrides continue to vie for attention as materials in multiple technological applications including hydrogen storage media, thermal energy storage (TES) materials, and hydrogen compressors. These applications depend on the temperature at which the materials desorb and reabsorb hydrogen. Magnesium hydride is ideal as a TES material, although its practical operating temperature is capped at ∼450 °C because of material degradation and high operating pressure. Fluorine substitution for hydrogen in magnesium hydride has previously been shown to increase the operating temperature of the metal hydride while limiting degradation, although full characterization is required before technological application can be ensured. The present study characterizes Mg(HxF1-x)2 solid solutions (x = 1, 0.95, 0.70, 0.85, 0.50, and 0) by inelastic neutron spectroscopy, powder X-ray diffraction, and thermal conductivity measurements, with the results being verified by density functional theory. For each experiment, a clear trend is observed throughout a series of solid solutions, showing the possibility of tuning the properties of MgH2. As F- substitution increases, the average Mg-H(F) bond distance elongates along the axial positions of the Mg-H(F) octahedra. Overall, this leads to an increase in Mg-H bond strength and thermal stability, improving the viability of Mg-H-F as potential TES materials. © 2020 American Chemical Society.
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    High ionic conductivity and dendrite-resistant NASICON solid electrolyte for all-solid-state sodium batteries
    (Elsevier, 2021-06-01) Shen, L; Yang, J; Liu, G; Avdeev, M; Yao, X
    The low ionic conductivity and poor dendrites suppression capability of Na3Zr2Si2PO12 solid electrolyte limit the practical application of all-solid-state sodium batteries. Herein, the optimized Na3.4Mg0.1Zr1.9Si2.2P0.8O12 electrolyte is obtained by simultaneously substituting the Zr4+ with Mg2+ and P5+ with Si4+ through solid-state reaction. The Na3.4Mg0.1Zr1.9Si2.2P0.8O12 electrolyte has superior room temperature ionic conductivity of 3.6 × 10−3 S cm−1, which is 17 times higher than that of pristine Na3Zr2Si2PO12. No short circuit of the Na/Na3.4Mg0.1Zr1.9Si2.2P0.8O12/Na symmetric battery is observed up to 2.0 mA cm−2, and the symmetric battery displays stable sodium plating/stripping cycles for over 2000 h at 0.1 mA cm−2 and 300 h at 1.0 mA cm−2. The resultant Na3.4Mg0.1Zr1.9Si2.2P0.8O12 electrolyte is further employed in two all-solid-state sodium batteries. The Na3V2(PO4)3/Na3.4Mg0.1Zr1.9Si2.2P0.8O12/Na all-solid-state sodium battery maintains a discharge capacity of 93.3 mAh g−1 at 0.1C after 50 cycles, and the FeS2/Na3.4Mg0.1Zr1.9Si2.2P0.8O12/Na all-solid-state sodium battery delivers a discharge capacity of 173.1 mAh g−1 at 0.1C after 20 cycles, which are significantly enhanced compared with those based on pristine Na3Zr2Si2PO12. This strategy provides an efficient method to prepare optimized NASICON solid electrolytes with high ionic conductivity and excellent dendrites suppression capability and promotes the practical application of all-solid-state sodium batteries. © 2021 Elsevier Ltd.
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    High-throughput computational screening of Li-containing fluorides for battery cathode coatings
    (American Chemical Society, 2020-12-16) Liu, B; Wang, D; Avdeev, M; Shi, S; Yang, J; Zhang, WQ
    Cathode degradation is a key factor that limits the cycling stability and rate capability of Li-ion batteries. Coating the surface of cathode particles with metal oxides or fluorides has been reported to suppress this degradation. However, poor Li-ion conductivity of metal oxide and fluoride coatings typically decreases the overall ionic conductivity. In addition, side (electro)chemical reactions at the coating/cathode interface and coating/hydrofluoric acid liquid environment also limit the performance of Li-ion batteries. Identification of stable coating materials with high Li-ion conductivity, which is typically done via a trial-and-error approach, remains a challenge. In this work, we perform high-throughput computational screening of ternary Li-containing fluorides for application as cathode coatings for Li-ion batteries, focusing on their phase stability, electrochemical stability, chemical stability, and Li-ion conductivity. Using the tiered screening approach, we identify 10 promising coating candidates from all the 920 Li-containing fluorides listed in the Materials Project database, including the two experimentally studied Li2ZrF6 and Li2TiF6 compounds. The identified cathode coatings are expected to exhibit optimal battery cycling and rate performance. In particular, Li2MF6 (M = Si, Ge, Zr, Ti) compounds offer the best combination of electrochemical and chemical stability and ionic conductivity, surpassing the performance of common coatings such as oxides and binary fluorides. © 2019 American Chemical Society
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    HRTex: a high-resolution texture data processing tool for monochromatic neutron diffraction based on the pixel projection method
    (International Union of Crystallography, 2022-04) Yang, J; Zhong, SY; Luzin, V; Liu, XL; Dan, C
    HRTex is a new texture data processing tool for two-dimensional position-sensitive area detectors on monochromatic neutron diffractometers. With the aim of improving the resolution and accuracy of pole figure calculations, HRTex treats the raw data of the area detector for each pixel and projects the intensity of each pixel directly onto a high-resolution pole figure. With the resultant refinement of the resolution, HRTex can distinguish close texture peaks with a flexible resolution setting and reduced information loss. Test results of HRTex on the data sets of two samples measured by two different neutron facilities are analysed, and the improvements in accuracy, resolution and efficiency of the pole figure calculation are discussed. © 2022 International Union of Crystallography
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    Liquid-metal-assisted deposition and patterning of molybdenum dioxide at low temperature
    (American Chemical Society, 2021-11-10) Wang, Y; Mayyas, M; Yang, J; Ghasemian, MB; Tang, J; Mousavi, M; Han, J; Ahmed, M; Baharfar, M; Mao, G; Yao, Y; Esrafilzadeh, D; Cortie, DL; Kalantar-Zadeh, K
    Molybdenum dioxide (MoO2), considering its nearmetallic conductivity and surface plasmonic properties, is a great material for electronics, energy storage devices and biosensing. Yet to this day, room-temperature synthesis of large area MoO2, which allows deposition on arbitrary substrates, has remained a challenge. Due to their reactive interfaces and specific solubility conditions, gallium-based liquid metal alloys offer unique opportunities for synthesizing materials that can meet these challenges. Herein, a substrate-independent liquid metal-based method for the room temperature deposition and patterning of MoO2 is presented. By introducing a molybdate precursor to the surrounding of a eutectic gallium-indium alloy droplet, a uniform layer of hydrated molybdenum oxide (H2MoO3) is formed at the interface. This layer is then exfoliated and transferred onto a desired substrate. Utilizing the transferred H2MoO3 layer, a laser-writing technique is developed which selectively transforms this H2MoO3 into crystalline MoO2 and produces electrically conductive MoO2 patterns at room temperature. The electrical conductivity and plasmonic properties of the MoO2 are analyzed and demonstrated. The presented metal oxide room-temperature deposition and patterning method can find many applications in optoelectronics, sensing, and energy industries. © 2021 American Chemical Society
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    Magnetic structure and metamagnetic transitions in the van der Waals antiferromagnet CrPS4
    (Wiley, 2020-06-05) Peng, YX; Ding, SL; Cheng, M; Hu, QF; Yang, J; Wang, FG; Xue, MZ; Liu, Z; Lin, ZC; Avdeev, M; Hou, YL; Yang, WY; Zheng, Y; Yang, JB
    In 2D magnets, interlayer exchange coupling is generally weak due to the van der Waals layered structure but it still plays a vital role in stabilizing the long-range magnetic ordering and determining the magnetic properties. Using complementary neutron diffraction, magnetic, and torque measurements, the complete magnetic phase diagram of CrPS4 crystals is determined. CrPS4 shows an antiferromagnetic ground state (A-type) formed by out-of-plane ferromagnetic monolayers with interlayer antiferromagnetic coupling along the c axis below TN = 38 K. Due to small magnetic anisotropy energy and weak interlayer coupling, the low-field metamagnetic transitions in CrPS4, that is, a spin-flop transition at ≈0.7 T and a spin-flip transition from antiferromagnetic to ferromagnetic under a relatively low field of 8 T, can be realized for H∥c. Intriguingly, with an inherent in-plane lattice anisotropy, spin-flop-induced moment realignment in CrPS4 for H∥c is parallel to the quasi-1D chains of CrS6 octahedra. The peculiar metamagnetic transitions and in-plane anisotropy make few-layer CrPS4 flakes a fascinating platform for studying 2D magnetism and for exploring prototype device applications in spintronics and optoelectronics. © 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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    Manipulation of planar oxygen defect arrangements in multifunctional magnèli titanium oxide hybrid systems: from energy conversion to water treatment
    (Royal Society of Chemistry, 2020-10-28) Liu, YC; Yang, J; Liu, Y; Zheng, J; Lee, W; Shi, JJ; Horlyck, J; Xie, JZ; Tay, YY; Tan, TT; Yu, DH; Mole, RA; McIntyre, GJ; Zhang, CY; Toe, CY; Waite, TD; Scott, J; Wang, Y; Wu, T; Han, SH; Li, S
    An extremely close relationship exists between energy usage and water supply with a tremendous amount of energy being consumed to process water for drinking and other purposes. The current energy crisis and inefficient water management place enormous stress on the sustainability of our society and environment. As such, the development of high-efficiency, cost-effective, and environmentally friendly materials which possess co-existing functionalities for applications ranging from energy capture to water treatment in one material, provides an opportunity to achieve sustainable development. As multifunctional materials, the layer-structured Magnèli titanium oxides with stoichiometry of TinO2n−1 (n ≥ 2) have been extensively studied in view of their potential for photocatalytic, thermoelectric and photothermal applications over the past few years. This group of materials occurs naturally as layered structures with planar oxygen defects, however, understanding of the correlation between the planar arrangements of the oxygen defects and various energy-related properties remains limited. Here, we demonstrate how the formation of layer structured TinO2n−1 with various planar oxygen defect arrangements correlates with the changes of their physical and chemical properties. The experimental results from inelastic neutron scattering analysis and electrical characterizations provide evidence that the planar oxygen defects are responsible for phonon scattering and exert a strong influence on their electrical conductivities. Manipulating these planar defects allows interconversion between different phases, which changes the interplay between electronic and phononic sub-systems. These manipulations potentially enable optimization of the corresponding physical properties of these materials such that they are rendered suitable for applications that require co-operative multifunctionality. More specifically, the experimental results demonstrate that the valence band positions and the onset potentials in the materials are raised, further enhancing their ability for catalysis of electrochemical reactions. This work also demonstrates the combinational effects of the thermoelectric and photothermal properties of these materials on their photocatalytic and electrochemical performance thereby providing a novel means of controlling the multi-response functionality of these materials for a variety of applications in different environments. © The Royal Society of Chemistry 2020
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    Two-dimensional quantum universality in the spin-1/2 triangular-lattice quantum antiferromagnet Na2BaCo(PO4)2
    (Proceedings of the National Academy of Sciences, 2022-12-15) Sheng, JM; Wang, L; Candini, A; Jiang, W; Huang, L; Xi, B; Zhao, J; Ge, H; Zhao, N; Fu, Y; Ren, J; Yang, J; Miao, P; Tong, X; Yu, D; Wang, S; Liu, Q; Kofu, M; Mole, RA; Biasiol, G; Yu, DH; Zaliznyak, IA; Mei, JW; Wu, L
    An interplay of geometrical frustration and strong quantum fluctuations in a spin-1/2 triangular-lattice antiferromagnet (TAF) can lead to exotic quantum states. Here, we report the neutron-scattering, magnetization, specific heat, and magnetocaloric studies of the recently discovered spin-1/2 TAF Na2BaCo(PO4)2, which can be described by a spin-1/2 easy axis XXZ model. The zero-field neutron diffraction experiment reveals an incommensurate antiferromagnetic ground state with a significantly reduced ordered moment of about 0.54(2) μB/Co. Different magnetic phase diagrams with magnetic fields in the ab plane and along the easy c-axis were extracted based on the magnetic susceptibility, specific heat, and elastic neutron-scattering results. In addition, two-dimensional (2D) spin dispersion in the triangular plane was observed in the high-field polarized state, and microscopic exchange parameters of the spin Hamiltonian have been determined through the linear spin wave theory. Consistently, quantum critical behaviors with the universality class of d = 2 and νz = 1 were established in the vicinity of the saturation field, where a Bose–Einstein condensation (BEC) of diluted magnons occurs. The newly discovered quantum criticality and fractional magnetization phase in this ideal spin-1/2 TAF present exciting opportunities for exploring exotic quantum phenomena. © 2022 the Author(s). Published by PNAS. This article is distributed under Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND).
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    Ultrastable all-solid-state sodium rechargeable batteries
    (American Chemical Society, 2020-08-11) Yang, J; Liu, G; Avdeev, M; Wan, H; Han, F; Shen, L; Zou, Z; Shi, S; Hu, YS; Wang, CS; Yao, X
    The insufficient ionic conductivity of oxide-based solid electrolytes and the large interfacial resistance between the cathode material and the solid electrolyte severely limit the performance of room-temperature all-solid-state sodium rechargeable batteries. A NASICON solid electrolyte Na3.4Zr1.9Zn0.1Si2.2P0.8O12, with superior room-temperature conductivity of 5.27 × 10–3 S cm–1, is achieved by simultaneous substitution of Zr4+ by aliovalent Zn2+ and P5+ by Si4+ in Na3Zr2Si2PO12. The bulk conductivity and grain boundary conductivity of Na3.4Zr1.9Zn0.1Si2.2P0.8O12 are nearly 20 times and almost 50 times greater than those of pristine Na3Zr2Si2PO12, respectively. The FeS2||polydopamine-Na3.4Zr1.9Zn0.1Si2.2P0.8O12||Na all-solid-state sodium batteries, with a polydopamine modification thin layer between the solid electrolyte and the cathode, maintain a high reversible capacity of 236.5 mAh g–1 at a 0.1 C rate for 100 cycles and a capacity of 133.1 mAh g–1 at 0.5 C for 300 cycles, demonstrating high performance for all-solid-state sodium batteries. © 2020 American Chemical Society