Dynamic Transport in Li-Conductive Polymer Electrolytes Plasticized with Poly(ethylene glycol)–Borate/Aluminate Ester

Authors

  • Fuminari Kaneko,

    1. Department of Applied Chemistry, Graduate School of Science and Engineering, Tokyo Institute of Technology, 2-12-1 Ookayama Meguro-ku Tokyo 152-8552 (Japan)
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  • Shinta Wada,

    1. Department of Applied Chemistry, Graduate School of Science and Engineering, Tokyo Institute of Technology, 2-12-1 Ookayama Meguro-ku Tokyo 152-8552 (Japan)
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  • Masanobu Nakayama,

    1. Department of Applied Chemistry, Graduate School of Science and Engineering, Tokyo Institute of Technology, 2-12-1 Ookayama Meguro-ku Tokyo 152-8552 (Japan)
    2. Department of Materials Science and Engineering, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Syowa-ku, Nagoya city, Aichi, 466-8555 (Japan), Fax: (+81) 52-735-5189
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  • Masataka Wakihara,

    1. Department of Applied Chemistry, Graduate School of Science and Engineering, Tokyo Institute of Technology, 2-12-1 Ookayama Meguro-ku Tokyo 152-8552 (Japan)
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  • Shigeki Kuroki

    1. Department of Chemistry and Materials Science, Graduate School of Science and Engineering, Tokyo Institute of Technology, 2-12-1 Ookayama Meguro-ku Tokyo 152-8552 (Japan)
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  • A Combined NMR and AC Impedance Study

Abstract

The addition of plasticizers into Li+-conductive solid polymer electrolytes (SPEs) is a commonly known technique to enhance the ionic conductivity. Among the used plasticizers, alkoxides of group-13 elements [such as poly(ethylene glycol) (PEG)–borate ester] are promising candidates due to the Lewis acidity of the elements of this group (i.e. B, Al, and so on), which interact with the anions and may increase the degree of dissociation of the salts and the transport number of the SPEs. By means of pulsed-gradient stimulated-echo NMR (PGStE-NMR) and AC impedance measurements, we investigate the effect of Lewis acidity originated from group-13 elements on the transport number and the dissociation rate of SPEs containing various plasticizers. Our results show that the degree of salt dissociation is significantly enhanced by the addition of plasticizers including group-13 elements, whereas only a small or negligible increase of the transport number is observed for these SPEs. We infer that the plasticizers exhibiting Lewis acidity associate with the anions, and that the associated pairs can migrate in the SPEs as fast as free anions, which results in a lower transport number than expected.

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