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Changes in electronic structure upon Li-ion extraction of LiMPO_4 (M=Fe,Co) using X-ray absorption spectroscopy and First Principle calculation

Research Project

Project/Area Number 16350109
Research Category

Grant-in-Aid for Scientific Research (B)

Allocation TypeSingle-year Grants
Section一般
Research Field Inorganic industrial materials
Research InstitutionKyoto University (2005-2006)
Tokyo Institute of Technology (2004)

Principal Investigator

UCHIMOTO Yoshiharu  Kyoto University, Graduate School of Human and Environmental Studies, Associate Professor, 大学院人間・環境学研究科, 助教授 (50193909)

Co-Investigator(Kenkyū-buntansha) WATANABE Iwao  Osaka Prefecture University, Graduate School of Science, Professor, 大学院理学系研究科, 教授 (50028239)
生田 博将  福島大学, 理工学群, 助教授 (80242270)
Project Period (FY) 2004 – 2006
Project Status Completed (Fiscal Year 2006)
Budget Amount *help
¥14,800,000 (Direct Cost: ¥14,800,000)
Fiscal Year 2006: ¥2,700,000 (Direct Cost: ¥2,700,000)
Fiscal Year 2005: ¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2004: ¥8,600,000 (Direct Cost: ¥8,600,000)
KeywordsElectronic structure / Lithium-ion batteries / First Principle calculation / Topochemical / Polyanion compounds / olivine type structure / リチウム電池 / X線吸収 / セラミックス / エネルギー効率化 / 表面・界面物性 / 正極活物質 / オリビン / 局所構造
Research Abstract

Li-ion secondary batteries have widely been utilized as consumers' electronic devices such as cellular phones, personal computers, etc. because of their high electrical density. A phosphate system, LiMPO_4 (M = Fe,Ni,Co) with the olivine-related structure, has recently been intensively studied as a candidate for positive electrodes. In the Olivine-type phosphate, it has been generally recognized that PO_4 polyanion units form their valence and conduction bands far from the Fermi level where an electronic exchange mainly occurs because of its closed shell electronic configuration. As a result, the transition-metal valence electrons tend to be isolated from those of polyanions, leading to the fact that the electronic exchange arising from Li removal/uptake mainly occurs at transition metal ions. The isolated transition-metal electronic structure would be the reason for the observed high voltage properties, and it simultaneously leads to the low electronic conductivities, causing technica … More l difficulties in fabrication of batteries. Thus, an understanding of their unique electronic structure is important to apply to rechargeable lithium-ion batteries.
Co,P, and 0 K-edge XAS measurements were carried out using synchrotron radiation at beam lines BL-7C,BL-11B, and BL-11A. In Co K-edge XANES around the threshold energy for electrochemically prepared samples, Li_<1-x>,CoPO_4, the threshold energy of LiCoPO_4 is close to that of a divalent reference sample, CoCO_3, the Co ions could be almost divalent in LiCoPO_4. The threshold energy gradually shifted to higher energy with charge reaction, indicating that Co ions are oxidized for the charge compensation over an entire region of the charge reaction (from x = 0.0 to 1.0). A absorption peak in P K-edge XANES gradually shifted with electrochemical Li removal, resulting an 0.2 eV shift at a composition of x = 1.0. This indicates that phosphate ions also contribute to the variation of the electronic structure and become less negative with charging. The results of 0 K-edge XANES of Li_<1-x>CoPO_4 indicate Ssarp absorption peaks appeared at the lower energy region. Since they are caused by the transition to hybridized unoccupied orbitals between the Co 3d and 0 2p orbitals, peak A is attributed to an absorption associated with the Co 3d-0 2p hybridized orbital. Peak A gradually shifted to lower energy at small x values (0 5_x approx. 0.5). The intensity of peak A increased with composition x, indicating an increase of holes at oxygen sites. Namely, the observed peak shift and the intensity increase of peak A indicate a decrease in d electron donation from the transition metal ions to hybridized orbitals. In addition, only a little variation was observed at the 0 K-edge XAS in the region of x 【approximately equal】0.5 which is a one-to-one correspondence to that observed in the Co K-edge XANES. Therefore, the oxide ions only contribute to charge compensation process at an early stage of lithium extraction, while the cobalt ions contribute to it at a later stage of the reaction.
The analysis of XANES for Li_<1-x>CoPO_4 shows that two effects would be responsible for the modification of the electronic structure of PO_4 polyanion, (1) the hybridization effect between the Co 3d and 0 2p orbitals, and (2) the polarization effect induced by strong ionic character of Li ions. The variation of the Co-, P-and 0 K-edge XANES reveals the important role of the hybridization between the Co and 0 ions and of the polarization in Li-O-P sequences. Less

Report

(4 results)
  • 2006 Annual Research Report   Final Research Report Summary
  • 2005 Annual Research Report
  • 2004 Annual Research Report
  • Research Products

    (9 results)

All 2007 2006 2005 2004

All Journal Article (9 results)

  • [Journal Article] Changes in Electronic Structure upon Lithium Insertion into Fe_2(SO_4)_3 and Fe_2(MoO_4)_3 Investigated by X-ray Absorption Spectroscopy2007

    • Author(s)
      J.Shirakawa, M.Nakayama, M.Wakihara, Y.Uchimoto
    • Journal Title

      J. Phys. Chem. B. 111

      Pages: 1424-1424

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2006 Final Research Report Summary
  • [Journal Article] Changes in Electronic Structure upon Lithium Insertion into Fe_2(SO_4)_3 and Fe_2(MoO_4)_3 Investigated by X-ray Absorption Spectroscopy2007

    • Author(s)
      J.Shirakawa, M.Nakayama, M.Wakihara, Y.Uchimoto
    • Journal Title

      J.Phys.Chem.B. 111

      Pages: 1424-1430

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2006 Final Research Report Summary
  • [Journal Article] Multiple Scattering Calculation for Co K-edge XANES Spectra of Nanometer Scale Metal Deposited during Li Insertion into LiCoVO_42006

    • Author(s)
      J.Shirakawa, M.Nakayama, Y.Uchimoto, M.Wakihara
    • Journal Title

      Electrochem. Solid State Lett. 9

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2006 Final Research Report Summary
  • [Journal Article] Changes in Electronic Structure upon Li Insertion Reaction of monoclinic Li_3Fe_2(PO_4)_32006

    • Author(s)
      J.Shirakawa, M.Nakayama, M.Wakihara, Y.Uchimoto
    • Journal Title

      J. Phys. Chem. B 110

      Pages: 17743-17743

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2006 Final Research Report Summary
  • [Journal Article] Multiple Scattering Calculation for Co K-edge XANES Spectra of Nanometer Scale Metal Deposited during Li Insertion into LiCoVO_42006

    • Author(s)
      J.Shirakawa, M.Nakayama, Y.Uchimoto, M.Wakihara
    • Journal Title

      Electrochem.Solid State Lett. 9

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2006 Final Research Report Summary
  • [Journal Article] Changes in Electronic Structure upon Li Insertion Reaction of monoclinic Li_3Fe_2(PO_4)_32006

    • Author(s)
      J.Shirakawa, M.Nakayama, M.Wakihara, Y.Uchimoto
    • Journal Title

      J.Phys.Chem.B 110

      Pages: 17743-17743

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2006 Final Research Report Summary
  • [Journal Article] X-Ray Absorption Spectroscopic Study on Electron Exchange in Li_<1-x>CoPO_4 Electrodes as 4.8 V Positive Electrodes for Rechargeable Lithium Ion Batteries2005

    • Author(s)
      M.Nakayama, S.Goto, Y.Uchimoto, M.Wakihara, Y.Kitajima, T.Miyanaga, I.Watanabe
    • Journal Title

      J. Phys. Chem. B 109

      Pages: 11197-11197

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2006 Final Research Report Summary
  • [Journal Article] X-Ray Absorption Spectroscopic Study on Electron Exchange in Li_<1-x>CoPO_4 Electrodes as 4.8 V Positive Electrodes for Rechargeable Lithium Ion Batteries2005

    • Author(s)
      M.Nakayama, S.Goto, Y.Uchimoto, M.Wakihara, Y.Kitajima, T.Miyanaga, I.Watanabe
    • Journal Title

      J.Phys.Chem.B 109

      Pages: 11197-11197

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2006 Final Research Report Summary
  • [Journal Article] Changes in Electronic Structure of Li_<1-x>CoPO_4 as 4.8 V Material using X-ray Absoprtion Spectroscopy2004

    • Author(s)
      Yoshiharu Uchimoto 他
    • Journal Title

      Chemistry of Materials 16

      Pages: 3399-3401

    • Related Report
      2004 Annual Research Report

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Published: 2004-04-01   Modified: 2016-04-21  

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