Browsing by Author "Yamada, A"

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    Inside Back Cover: t-Na2(VO)P2O7: A 3.8 V pyrophosphate insertion material for sodium-ion batteries
    (Wiley, 2014-06-23) Barpanda, P; Liu, G; Avdeev, M; Yamada, A
    Pyrophosphate oxyanionic framework compounds offer a great platform to investigate new battery materials. In our continuing effort to explore pyrophosphate cathodes for sodium-ion batteries, we report, for the first time, the synthesis and use of tetragonal Na2(VO)P2O7 as a potential sodium-ion insertion material. This material can be easily prepared by using a conventional solid-state route at a relatively low temperature of 400 °C. Stabilizing as a tetragonal structure with an open framework, the material offers pathways for Na+ diffusion. The as-synthesized material, with no further cathode optimization, yields a reversible capacity (Q) approaching 80 mAh g−1 (QTheoretical=93.4 mAh g−1) involving a one electron V5+/V4+ redox potential located at 3.8 V (vs. Na/Na+). Furthermore, the material exhibits decent rate kinetics and reversibility. Combining green synthesis and moderate electrochemical properties, t-Na2(VO)P2O7 is reported as a new addition to the growing family of pyrophosphate cathodes for sodium-ion batteries.© 2014, WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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    Magnetic structure and properties of the Na2CoP2O7 pyrophosphate cathode for sodium-ion batteries: a supersuperexchange-driven non-collinear antiferromagnet
    (American Chemical Society, 2012-12-17) Barpanda, P; Avdeev, M; Ling, CD; Lu, J; Yamada, A
    The crystal and magnetic structure and properties of the Na2CoP2O7 Na+-ion battery cathode material have been characterized by magnetic susceptibility, specific heat, and variable-temperature neutron powder diffraction measurements. Na2CoP2O7 crystallizes in the orthorhombic space group Pna21 with a = 15.4061(3) Å, b = 10.28854(9) Å, and c = 7.70316(15) Å, having a layered structure with slabs of [CoP2O7]∞ separated by Na cations. The magnetic property measurements and neutron diffraction data analysis reveal that the material undergoes long-range ordering to a noncollinear antiferromagnetic G-type structure below TN ≈ 6.5 K. The magnetic structure is rationalized as a result of supersuperexchange between Co2+ atoms linked by phosphate groups.© 2013, American Chemical Society.
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    Magnetic structure and properties of the rechargeable battery insertion compound Na2FePO4F
    (American Chemical Society, 2013-12-26) Avdeev, M; Ling, CD; Tan, TT; Li, S; Oyama, G; Yamada, A; Barpanda, P
    The magnetic structure and properties of sodium iron fluorophosphate Na2FePO4F (space group Pbcn), a cathode material for rechargeable batteries, were studied using magnetometry and neutron powder diffraction. The material, which can be described as a quasi-layered structure with zigzag Fe-octahedral chains, develops a long-range antiferromagnetic order below ∼3.4 K. The magnetic structure is rationalized as a super-exchange-driven ferromagnetic ordering of chains running along the a-axis, coupled antiferromagnetically by super-super-exchange via phosphate groups along the c-axis, with ordering along the b-axis likely due to the contribution of dipole–dipole interactions. © 2013 American Chemical Society
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    Magnetic structure of some battery materials and why it matters
    (International Battery Materials Association, 2014-03-02) Avdeev, M; Ling, CD; Mohamed, Z; Barpanda, P; Yamada, A; Ben Yahia, H; Shikano, M
    Operation of batteries with insertion cathodes is typically based on a redox reaction Mn+/Mn+p (p=1,2) of transition metals. The motivation to increase gravimetric energy density and reduce cost naturally drives research to the light, i.e. 3d, transition metals M=V-Ni, which in turn are also paramagnetic ions and may order magnetically. Using neutron diffraction and magnetometry we explored magnetic structure and properties of some materials recently synthesized in search of better cathode materials: Na2CoP2O7, maricite- and triphylite-NaFePO4, Na2FePO4F, M(OH)xF2-x (M=Co,Fe), Li2MnSiO4, Li2CoSiO4, LiNaCoPO4F, LiNaFePO4F. The detailed magnetic structures will be presented and features of crystal structures affecting the type of magnetic ordering will be discussed. Although polyanionic materials (phosphates and silicates) are magnetically low density systems and thus order at low temperature (< 50 K), the information on magnetic structure is important for accurate DFT calculations. The effect of neglecting magnetic order on the DFT based quantitative predictions will be illustrated.
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    Magnetic structures of NaFePO4 maricite and triphylite polymorphs for sodium-ion batteries
    (American Chemical Society, 2013-08-05) Avdeev, M; Mohamed, Z; Ling, CD; Lu, J; Tamaru, M; Yamada, A; Barpanda, P
    The magnetic structure and properties of polycrystalline NaFePO4 polymorphs, maricite and triphylite, both derived from the olivine structure type, have been investigated using magnetic susceptibility, heat capacity, and low-temperature neutron powder diffraction. These NaFePO4 polymorphs assume orthorhombic frameworks (space group No. 62, Pnma), built from FeO6 octahedral and PO4 tetrahedral units having corner-sharing and edge-sharing arrangements. Both polymorphs demonstrate antiferromagnetic ordering below 13 K for maricite and 50 K for triphylite. The magnetic structure and properties are discussed considering super- and supersuperexchange interactions in comparison to those of triphylite-LiFePO4. © 2013, American Chemical Society
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    Na2FeP2O7: a safe cathode for rechargeable sodium-ion batteries
    (American Chemical Society, 2013-09-10) Barpanda, P; Liu, G; Ling, CD; Tamaru, M; Avdeev, M; Chung, SC; Yamada, Y; Yamada, A
    Vying for newer sodium-ion chemistry for rechargeable batteries, Na2FeP2O7 pyrophosphate has been recently unveiled as a 3 V high-rate cathode. In addition to its low cost and promising electrochemical performance, here we demonstrate Na2FeP2O7 as a safe cathode with high thermal stability. Chemical/electrochemical desodiation of this insertion compound has led to the discovery of a new polymorph of NaFeP2O7. High-temperature analyses of the desodiated state NaFeP2O7 show an irreversible phase transition from triclinic (P (1) over bar) to the ground state monoclinic (P2(1)/c) polymorph above 560 degrees C. It demonstrates high thermal stability, with no thermal decomposition and/or oxygen evolution until 600 degrees C, the upper limit of the present investigation. This high operational stability is rooted in the stable pyrophosphate (P2O7)(4-) anion, which offers better safety than other phosphate-based cathodes. It establishes Na2FeP2O7 as a safe cathode candidate for large-scale economic sodium-ion battery applications. © 2013, American Chemical Society.
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    Neutron diffraction study of the li-ion battery cathode Li2FeP2O7
    (American Chemical Society, 2013-03-18) Barpanda, P; Rousse, G; Ye, T; Ling, CD; Mohamed, Z; Klein, Y; Yamada, A
    With a combination of magnetic susceptibility measurements and low-temperature neutron diffraction analyses, the magnetic structure of Li2FeP2O7 cathode has been solved. This pyrophosphate Li2FeP2O7 compound stabilizes into a monoclinic framework (space group P2(1)/c),having a pseudolayered structure with the constituent Li/Fe sites distributed into MO6 and MO5 building units. The magnetic susceptibility follows a Curie Weiss behavior above 50 K. Li2FeP2O7 shows a long-range antiferromagnetic ordering at T-N = 9 K, as characterized by the appearance of distinct additional peaks in the neutron diffraction pattern below TN. Its magnetic reflections can be indexed with a propagation vector k = (0,0,0). The magnetic moments inside the FeO6-FeO5 clusters are ferromagnetic, whereas these clusters are antiferromagnetic along the chains. The adjacent chains are in turn ferromagnetically arranged along the a-axis. The magnetic structure of Li2FeP2O7 cathode material is described focusing on their localized spin spin exchange. The magnetic structure and properties have been generalized for Li2FeP2O7 Li2CoP2O7 binary solid solutions. © 2013, American Chemical Society.
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    A new polymorph of Na2MnP2O7 as a 3.6 V cathode material for sodium-ion batteries
    (Royal Society of Chemistry, 2013-01-01) Barpanda, P; Ye, T; Avdeev, M; Chung, SC; Yamada, A
    Exploring novel low-cost cathodes for sodium-ion batteries, here we unveil [small beta]-Na2MnP2O7, a new pyrophosphate cathode. Stabilizing into a triclinic structure, it was found to be electrochemically active, delivering a discharge capacity approaching 80 mA h g-1 along with the highest ever Mn3+/Mn2+ redox potential located at 3.6 V. © 2013, Royal Society of Chemistry
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    t-Na2(VO)P2O7: A 3.8 V Pyrophosphate insertion material for sodium-ion batteries (ChemElectroChem 9/2014)
    (Wiley, 2014-09-04) Barpanda, P; Liu, G; Avdeev, M; Yamada, A
    The picture shows a bond valence sum map of a fresnoite Na2(VO)P2O7 cathode that acts as a novel 3.8 V insertion host material for sodium-ion batteries. This work is presented on p. 1488 by P. Barpanda, A. Yamada et al. © 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim