| 1. |
- Blomqvist, Andreas, et al.
(författare)
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Hydrogen as promoter and inhibitor of superionicity : A case study on Li-N-H systems
- 2010
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121. ; 82:2, s. 024304
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Tidskriftsartikel (refereegranskat)abstract
- Materials which possess a high lithium ion conductivity are very attractive for battery and fuel cell applications. Hydrogenation of the fast-ion conductor lithium nitride (Li3N) leads to the formation of lithium imide (Li2NH) and subsequently of lithium amide (LiNH2). Using ab initio molecular dynamics simulations, we carried out a comparative study of the Li diffusion in these three systems. The results demonstrate that hydrogen can work as both promoter and inhibitor of Li mobility, with the lowest transition temperature to the superionic state occurring in Li2NH. Furthermore, we show that the creation of Li vacancies strongly affects Li diffusion in Li3N, but not so in Li2NH. Finally, we explain our findings with the help of a simple model.
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| 2. |
- Li, Wen, et al.
(författare)
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Li+ ion conductivity and diffusion mechanism in α-Li3N and β-Li3N
- 2010
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Ingår i: Energy & environmental science. - 1754-5692. ; 3:10, s. 1524-1530
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Tidskriftsartikel (refereegranskat)abstract
- beta-Li3N of hexagonal D-6h(4) (P6(3)/mmc) structure was synthesized by high-energy ball milling commercial Li3N (composed of both alpha and beta phases). Ionic conductivities of alpha-Li3N and beta-Li3N were tested by direct current (D. C.) and alternating current (A. C.) impedance methods. beta-Li3N exhibited the same order of magnitude of Li+ ion conductivity (2.085 x 10(-4) S cm(-1)) as that of alpha-Li3N (5.767 x 10(-4) S cm(-1)) at room temperature. First-principles calculations were employed to simulate the diffusion mechanism of Li+ ion in alpha-Li3N and beta-Li3N. Our results indicate that the diffusion of Li+ ion in beta-Li3N likely occurs between pure Li-beta(1) planes, which is different from that in alpha-Li3N, where the diffusion of Li+ ion occurs within Li2N plane. The Li+ ion migration energy barriers (E-m) for alpha-Li3N and beta-Li3N are 0.007 eV and 0.038 eV, respectively.
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| 3. |
- Li, Wen, et al.
(författare)
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Li-Na ternary amidoborane for hydrogen storage : experimental and first-principles study
- 2012
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Ingår i: Dalton Transactions. - 1477-9226. ; 41:16, s. 4754-4764
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Tidskriftsartikel (refereegranskat)abstract
- Li-Na ternary amidoborane, Na[Li(NH2BH3)(2)], was recently synthesized by reacting LiH and NaH with NH3BH3. This mixed-cation amidoborane shows improved dehydrogenation performance compared to that of single-cation amidoboranes, i.e., LiNH2BH3 and NaNH2BH3. In this paper, we synthesized the Li-Na ternary amidoborane by blending and re-crystallizing equivalent LiNH2BH3 and NaNH2BH3 in tetrahydrofuran (THF), and employed first-principles calculations and the special quasirandom structure (SQS) method to theoretically explore the likelihood for the existence of Li1-xNax(NH2BH3) for various Li/Na ratios. The thermodynamic, electronic and phononic properties were investigated to understand the possible dehydrogenation mechanisms of Na[Li(NH2BH3)(2)].
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| 4. |
- Li, Wen, et al.
(författare)
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Understanding from First-Principles Why LiNH2BH3 · NH3BH3 Shows Improved Dehydrogenation over LiNH2BH3 and NH3BH3
- 2010
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Ingår i: The Journal of Physical Chemistry C. - 1932-7447. ; 114:44, s. 19089-19095
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Tidskriftsartikel (refereegranskat)abstract
- Lithium amidoborane-ammonia borane (LiNH2BH3 center dot NH3BH3, LiAB center dot AB for short) was synthesized recently. Compared with lithium amidoborane (LiNH2BH3, LiAB for short) and ammonia borane (NH3BH3, AB for short), this new ammonia borane derivative has better dehydrogenation kinetics and releases 14.8 wt % hydrogen with peak temperatures at ca. 80 and 140 degrees C, respectively. In this report, first-principles calculations were employed to reveal the differences in dehydrogenation properties of AB, LiAB, and LiAB center dot AB. Furthermore, we attempted to correlate the crystal structure and electronic properties with dehydrogenation performance. The results show that Li+ cations play similar roles in LiAB center dot AB as in LiAB in destabilizing the B-H and N-H bonds, and the mechanism of the first-step dehydrogenation of LiAB center dot AB is likely via the dissociation and combination of hydridic H delta-(B) from LiAB molecule and protonic H delta+(N) from the adjacent AB molecule, rather than from the [LiAB] or [AB] layer alone, resulting in the desorption of H-2 at lower temperatures.
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| 5. |
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