The effect of cation size on hydride-ion conduction in LnSrLiH2O2 (Ln = La, Pr, Nd, Sm, Gd) oxyhydrides

Naoki Matsui; Yoyo Hinuma; Yuki Iwasaki; Kota Suzuki; Jiang Guangzhong; Haq Nawaz; Yumiko Imai; Masao Yonemura; Masaaki Hirayama; Genki Kobayashi; Ryoji Kanno

doi:10.1039/D0TA06728H

The effect of cation size on hydride-ion conduction in LnSrLiH₂O₂ (Ln = La, Pr, Nd, Sm, Gd) oxyhydrides†

Naoki Matsui,

^a Yoyo Hinuma,

^ab Yuki Iwasaki,^c Kota Suzuki,

^ac Jiang Guangzhong,^a Haq Nawaz,^de Yumiko Imai,^d Masao Yonemura,^f Masaaki Hirayama,^ac Genki Kobayashi

^de and Ryoji Kanno*^ac

Author affiliations

* Corresponding authors

^a All-Solid-State Battery Unit, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohma 226-8503, Japan
E-mail: kanno@echem.titech.ac.jp

^b Center for Frontier Science, Chiba University, 1-33 Yayoi-cho, Inage, Chiba 263-8522, Japan

^c Department of Chemical Science and Engineering, School of Materials and Chemical Technology, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8502, Japan

^d Department of Materials Molecular Science, Institute for Molecular Science, National Institute of Natural Sciences, 38 Nishigonaka, Myodaiji, Okazaki, Aichi, Japan

^e SOKENDAI (The Graduate University for Advanced Studies), 38 Nishigonaka, Myodaiji, Okazaki, Aichi, Japan

^f Neutron Science Laboratory (KENS), Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan

Abstract

Hydride-ion conductors have attracted great interest as solid electrolytes due to the highly negative redox potential of the hydride ion. This study provides direction for effective design of materials that enhance H⁻ conductivity by exploring the relationship between cation size and hydride-ion conductivity using LnSrLiH₂O₂ (Ln = La, Pr, Nd, Sm, Gd), which are K₂NiF₄-type oxyhydride materials, synthesised under ambient and high pressures. The size of the A-site cation and the activation energy for H⁻ conduction were found to be strongly correlated. GdSrLiH₂O₂ exhibits the lowest activation energy of 67 kJ mol⁻¹. Crystal structure analysis and first principles calculations revealed that H⁻ is more displaced along the conduction pathway for smaller A-site cations in LnSrLiH₂O₂ due to lower repulsion between A-site cations and H⁻. These findings contribute to the further development of K₂NiF₄-type oxyhydrides with high H⁻ conductivities.

Journal of Materials Chemistry A

The effect of cation size on hydride-ion conduction in LnSrLiH₂O₂ (Ln = La, Pr, Nd, Sm, Gd) oxyhydrides†

Abstract

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The effect of cation size on hydride-ion conduction in LnSrLiH₂O₂ (Ln = La, Pr, Nd, Sm, Gd) oxyhydrides

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Journal of Materials Chemistry A