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Published on: December 20, 2016
A trade-off between migration and association energies for hydride-ion conductivity in the SrLiH3-CaLiH3-NaLiH2
Takashi Hirose1, Naoki Matsui2, Kenta Watanabe1,2
1Department of Chemical Science and Engineering, School of Materials and Chemical Technology, Institute of Science Tokyo, 4259 Nagatsuta, Midori-ku, Yokohama 226-8501, Japan.
Abstract:
Hydride-ion (H-) conductors have garnered much attention owing to their high ionic conductivity and potential applications such as batteries and fuel/electrolysis cells. Perovskite-type H- conductors are known to exhibit relatively high ionic conductivity at room temperature. The present work demonstrated systematic material exploration within the SrLiH3-CaLiH3-NaLiH2 pseudo-ternary system. The Na-substituted system, Sr1-NaLiH3-, exhibited a remarkable H- conductivity of 5.1 × 10-6 S cm-1 at 25 °C for Sr0.8Na0.2LiH2.8, marking the highest value reported among perovskite-type hydrides to date. Furthermore, we found a clear trend of enhanced H- conductivity with Ca substitution in the Sr1-CaLiH3 pseudo-binary system. However, in the Sr1-CaNaLiH3- pseudo-ternary system, a negative synergistic effect of Ca and Na co-doping was observed. First-principles calculations revealed that this negative effect arises from a trade-off between migration and association energies in defect pairs of Na+ dopants and H- vacancies. These findings provide valuable insights into designing superior anion conductors.
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