Electronic structure of ternary hydrides based on light elements

Summary The properties of the complex hydrides LiBH4 and NaAlH4 such as structural, electronic, and optical properties were calculated using the augmented plane wave plus local orbitals (APW + lo) method. The three phases α, β, and γ of LiBH4 and NaAlH4 hydrides are studied, the β‐phase is transformed at the high‐pressure to γ phase for the compound LiBH4 with the generalized gradient approximation (GGA) with a 16% volume decrease. However, NaAlH4 compound did not show any phase transition. The interaction between the boron (aluminum) atoms and the hydrogen atoms in the [AlH4]− ([BH4]−) complexes is strongly covalent, and between the complexes [AlH4]− and the lithium Li+ cations for the LiBH4 compound and between the complexes [AlH4]− and the sodium Na+ cations for the NaAlH4 compound, the bond is ionic. For the most stable phases of the two complex hydrides, different optical parameters have been calculated as a function of the photon energy. The plasma frequency ωp is calculated from the mean peak of the energy loss function. Therefore, by way of example, the plasma energy ħωp of its peak position is 13.23 (12.93) eV for α‐NaAlH4 (α‐LiBH4).

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“…Table shows the values of the energy gap. According to previous studies, our values of the energy gap are acceptable.…”

Section: Resultssupporting

confidence: 69%

Electronic structure and optical properties of complex hydrides LiBH4 and NaAlH4 compounds

et al. 2019

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“…LiBH 4 undergoes a phase transition at approximately 390 K. The HT phase exhibits fast Li‐ionic conductivity of greater than 2 × 10 −3 S cm −1 , as shown in Figure (the numerical data are summarized in Table S5, Supporting Information). Large band gaps with approximately 6 eV both in the LT‐ and HT‐phase of LiBH 4 suggests the negligible contribution of the electronic conductivity in that material.…”

Section: Rechargeable Li‐ion Battery Development Using Complex Hydridmentioning

confidence: 99%

Complex Hydrides for Electrochemical Energy Storage

Unemoto

Matsuo

Orimo

2014

Adv Funct Materials

197

226

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Complex hydrides have energy storage-related functions such as i) solid-state hydrogen storage, ii) electrochemical Li storage, and iii) fast Li-and Naionic conductions. Here, recent progress on the development of fast Li-ionic conductors based on the complex hydrides is reported. The validity of using them as electrolytes in all-solid-state lithium rechargeable batteries is also examined. Not only coated oxides but also bare sulfi des are found to be applicable as positive electrode active materials. Results related to fast Na-ionic conductivity in the complex hydrides are presented. In the last section, the future prospects for battery assemblies with high-energy densities, and Mg ion batteries with the liquid and the solid-state electrolytes are discussed. Figure 1. Crystal structures of a) LT phase and b) HT phase of LiBH 4 . [ 16 ]Adv. FEATURE ARTICLEto fast Li-ionic conduction, the advantages of the use of complex hydrides as rechargeable battery electrolytes are as follows, iii) Fast Li-and Na-ionic conductions: One of the important challenges in the fi eld of battery research is the development of fast ionic conductors because this class of materials enables the assembly from micro- [ 24 ] to bulk-type [25][26][27] all-solid-state rechargeable cells, which allows the broader applications. With this background, various solid-state electrolytes have been developed so far, however, the materials showing suffi cient ionic conductivity as well as good stability in the voltage ranges for battery operation are limited to a few cases. [ 28 ] Therefore, novel solid-state electrolytes are urgently required for the development of future generation batteries. Since the discovery of fast Li-ionic conduction in the HT phase of LiBH 4 , [ 29 ] we have developed numerous solid-state electrolytes based on the complex hydrides that exhibit fast Li-and Na-ionic conductions. [ 30 ] Herein, we briefl y report recent progress in the development of the complex hydrides that exhibit fast Li-ionic conduction. All-solid-state Li rechargeable batteries were subsequently assembled using coated-LiCoO 2 and TiS 2 positive electrodes, and LiBH 4 -based electrolytes. The validity of the use of the complex hydrides as electrolytes in a rechargeable battery was examined on the basis of charge-discharge measurements. In the following section, our recent development of fast Na-ionic conductors based on the complex hydrides is summarized. We discuss the future prospects for the development of high energy density rechargeable batteries, and Mg-ion batteries that use nonaqueous and solid-state electrolytes based on the complex hydrides. FEATURE ARTICLEhexagonal phase of LiBH 4 (fast Li-ion conduction phase) even at room temperature when x exceeds 0.25. And then, the solid-solution, Li 4 (BH 4 ) 3 I, exhibits fast Li-ionic conductivity of 2 × 10 −5 S cm −1 at 300 K. [ 34,[51][52][53] This phenomenon might be due to increased neighboring distance of [BH 4 ] − [ 54 ] and induced lattice anharmonicity by the partial substitution of I − instead of ...

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“…There was a significant enhancement in self‐heating above the structural transition temperature of 390 K, which resulted in rapid hydrogen desorption above 600 K 13, 14. This phenomenon triggered the discovery of lithium fast‐ionic conduction in LiBH 4 15 because permittivity measurements suggested that the self‐heating of LiBH 4 was due to conductive loss,13 although LiBH 4 acts as an electrical insulator in both LT and HT phases with a large band gap of approximately 7 eV 3, 16…”

Section: Introductionmentioning

confidence: 99%

Lithium Fast‐Ionic Conduction in Complex Hydrides: Review and Prospects

Matsuo¹,

Orimo²

2011

Advanced Energy Materials

242

261

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Complex hydrides exhibit various energy-related functions such as hydrogen storage, microwave absorption, and neutron shielding. Furthermore, another novel energy-related function was recently reported by the authors; lithium fast-ionic conduction, which suggests that complex hydrides may be a potential candidate for solid electrolytes in lithium-ion batteries. This review presents the recent progress in the development of lithium fast-ionic conductors of complex hydrides. First, the fast-ionic conduction in LiBH 4 as a result of clarifying the mechanism of microwave absorption is presented, and then the conceptual development of complex hydrides as a new type of solid-state lithium fast-ionic conductors in LiBH 4 -, LiNH 2 -, and LiAlH 4 -based complex hydrides is discussed. Finally, the future prospects of this study from both application and fundamental viewpoints are described: possible use as solid electrolytes for batteries, formation of ionic liquids in complex hydrides, and similarity between complex hydrides and Laves-phase metal hydrides.Motoaki Matsuo and Shin-ichi Orimo* Figure 1 . Crystal structures of the a) LT and b) HT phases of LiBH 4 . [7][8][9]

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Electronic structure of ternary hydrides based on light elements

Cited by 21 publications

References 16 publications

Electronic structure and optical properties of complex hydrides LiBH4 and NaAlH4 compounds

Electronic structure and optical properties of complex hydrides LiBH4 and NaAlH4 compounds

Complex Hydrides for Electrochemical Energy Storage

Lithium Fast‐Ionic Conduction in Complex Hydrides: Review and Prospects

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