Mesopore size dependence of the ionic diffusivity in alumina based composite lithium ionic conductors

Hideki Maekawa, Yutaka Fujimaki, Hangyan Shen, Junichi Kawamura, Tsutomu Yamamura

Research output: Contribution to journalArticlepeer-review

41 Citations (Scopus)

Abstract

Ordered-mesoporous Al2O3 was synthesized by a sol-gel method using neutral copolymer surfactants as structure-directing agents. The pore size was controlled over the 3-15 nm range by the use of various surfactants. Composites composed of the synthesized mesoporous Al2O3 and a lithium ion conductor (LiI) were prepared. The maximum dc electrical conductivity, 2.6 × 10- 4 S cm- 1 at 298 K, was observed for 50 LiI·50 Al2O3 composite with 4.2 nm average mesopore size, which was considerably higher than the previously reported LiI-alumina composites. A systematic dependence of conductivity upon pore size was observed, in which conductivity increased with decreasing pore size, except for samples with a pore size of 2.8 nm. The lithium ion diffusion coefficient determined by the 7Li pulsed field gradient nuclear magnetic resonance (PFG-NMR) showed excellent agreement with the measured conductivity calculated by the Nernst-Einstein equation. On the other hand, lithium migration activation energies obtained by quasielastic neutron scattering (QENS) and 7Li NMR spin-lattice relaxation time (T1) were considerably smaller than those obtained from electrical conductivity and PFG-NMR. This could be explained by the ion migration mechanism in heterogeneous composites and a possible enhancement of conductivity in mesoscopically confined spaces.

Original languageEnglish
Pages (from-to)2711-2714
Number of pages4
JournalSolid State Ionics
Volume177
Issue number26-32 SPEC. ISS.
DOIs
Publication statusPublished - 2006 Oct 31

Keywords

  • Composite ionic conductor
  • Lithium iodide
  • Mesoporous alumina
  • Pore size dependence

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics

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