Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QR, UK.
Phys Chem Chem Phys. 2014 Mar 7;16(9):4061-70. doi: 10.1039/c4cp00087k.
We report the experimental investigation of hydrogen storage and release in the lithium amide-lithium hydride composite (Li-N-H) system. Investigation of hydrogenation and dehydrogenation reactions of the system through in situ synchrotron X-ray powder diffraction experiments allowed for the observation of the formation and evolution of non-stoichiometric intermediate species of the form Li1+xNH2-x. This result is consistent with the proposed Frenkel-defect mechanism for these reactions. We observed capacity loss with decreasing temperature through decreased levels of lithium-rich (0.7 ≤ x ≤ 1.0) non-stoichiometric phases in the dehydrogenated material, but only minor changes due to multiple cycles at the same temperature. Annealing of dehydrogenated samples reveals the reduced stability of intermediate stoichiometry values (0.4 ≤ x ≤ 0.7) compared with the end member species: lithium amide (LiNH2) and lithium imide (Li2NH). Our results highlight the central role of ionic mobility in understanding temperature limitations, capacity loss and facile reversibility of the Li-N-H system.
我们报告了在氨基锂-氢化锂复合（Li-N-H）体系中储氢和释氢的实验研究。通过原位同步辐射 X 射线粉末衍射实验研究了该体系的加氢和脱氢反应，观察到了形成和演化非化学计量中间物种的形式 Li1+xNH2-x。这一结果与这些反应的弗伦克尔缺陷机制一致。我们观察到随着温度的降低，脱氢材料中富锂（0.7≤x≤1.0）非化学计量相的水平降低，导致容量损失，但在相同温度下多次循环仅导致微小变化。脱氢样品的退火表明，与端基物质（LiNH2 和 Li2NH）相比，中间化学计量值（0.4≤x≤0.7）的稳定性降低。我们的结果强调了离子迁移率在理解 Li-N-H 体系的温度限制、容量损失和易还原方面的核心作用。
