Isolation of Solid Solution Phases in Size-Controlled LixFePO4 at Room Temperature

Authors

  • Genki Kobayashi,

    1. Department of Electronic Chemistry Interdisciplinary Graduate School of Science and Engineering Tokyo Institute of Technology 4259 Nagatsuta, Midori, Yokohama 226-8502 (Japan)
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  • Shin-ichi Nishimura,

    1. Department of Electronic Chemistry Interdisciplinary Graduate School of Science and Engineering Tokyo Institute of Technology 4259 Nagatsuta, Midori, Yokohama 226-8502 (Japan)
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  • Min-Sik Park,

    1. Department of Electronic Chemistry Interdisciplinary Graduate School of Science and Engineering Tokyo Institute of Technology 4259 Nagatsuta, Midori, Yokohama 226-8502 (Japan)
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  • Ryoji Kanno,

    1. Department of Electronic Chemistry Interdisciplinary Graduate School of Science and Engineering Tokyo Institute of Technology 4259 Nagatsuta, Midori, Yokohama 226-8502 (Japan)
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  • Masatomo Yashima,

    1. Department of Materials Science and Engineering Interdisciplinary Graduate School of Science and Engineering Tokyo Institute of Technology 4259 Nagatsuta, Midori, Yokohama 226-8502 (Japan)
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  • Takashi Ida,

    1. Ceramics Research Laboratory Nagoya Institute of Technology Asahigaoka, Tajimi 507-0071 (Japan)
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  • Atsuo Yamada

    Corresponding author
    1. Department of Electronic Chemistry Interdisciplinary Graduate School of Science and Engineering Tokyo Institute of Technology 4259 Nagatsuta, Midori, Yokohama 226-8502 (Japan)
    • Department of Electronic Chemistry Interdisciplinary Graduate School of Science and Engineering Tokyo Institute of Technology 4259 Nagatsuta, Midori, Yokohama 226-8502 (Japan).
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Abstract

State-of-the-art LiFePO4 technology has now opened the door for lithium ion batteries to take their place in large-scale applications such as plug-in hybrid vehicles. A high level of safety, significant cost reduction, and huge power generation are on the verge of being guaranteed for the most advanced energy storage system. The room-temperature phase diagram is essential to understand the facile electrode reaction of LixFePO4 (0 < x < 1), but it has not been fully understood. Here, intermediate solid solution phases close to x = 0 and x = 1 have been isolated at room temperature. Size-dependent modification of the phase diagram, as well as the systematic variation of lattice parameters inside the solid-solution compositional domain closely related to the electrochemical redox potential, are demonstrated. These experimental results reveal that the excess capacity that has been observed above and below the two-phase equilibrium potential is largely due to the bulk solid solution, and thus support the size-dependent miscibility gap model.

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