Particle-Size Effects on the Entropy Behavior of a LixFePO4 Electrode

Authors

  • Kazuhiko Kai,

    1. Department of Chemical System Engineering, School of Engineering, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-8656 (Japan)
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  • Dr. Yo Kobayashi,

    1. Central Research Institute of Electric Power Industry, Iwadokita 2-11-1, Komae, Tokyo 201-8511 (Japan)
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  • Dr. Hajime Miyashiro,

    1. Central Research Institute of Electric Power Industry, Iwadokita 2-11-1, Komae, Tokyo 201-8511 (Japan)
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  • Gosuke Oyama,

    1. Department of Chemical System Engineering, School of Engineering, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-8656 (Japan)
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  • Dr. Shin-ichi Nishimura,

    1. Department of Chemical System Engineering, School of Engineering, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-8656 (Japan)
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  • Dr. Masashi Okubo,

    1. Department of Chemical System Engineering, School of Engineering, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-8656 (Japan)
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  • Prof. Atsuo Yamada

    Corresponding author
    1. Department of Chemical System Engineering, School of Engineering, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-8656 (Japan)
    • Department of Chemical System Engineering, School of Engineering, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-8656 (Japan)===

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Abstract

The particle-size effects on the thermodynamic properties and kinetic behavior of a LixFePO4 electrode have a direct influence on the electrode properties. Thus, the development of high-performance Li-ion batteries containing a LixFePO4 cathode requires a complete understanding of the reaction mechanism at the atomic/nano/meso scale. In this work, we report electrochemical calorimetric and potentiometric studies on LixFePO4 electrodes with different particle sizes and clarify the particle-size effect on the reaction mechanism based on the entropy change of (de)lithiation. Electrochemical calorimetry results show that a reduction in particle size shrinks the miscibility gap of LixFePO4 while potentiometric measurements demonstrate that the LixFePO4 particles equilibrate into either a kinetically metastable state or a thermodynamically stable state depending on the particle size.

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