Paper Title:
Thermodynamic Characterization on Hydrogen Absorption and Desorption Reactions of Lithium – Silicon Alloy
  Abstract

Lithium hydride LiH is one of the attractive hydrogen storage materials, because it stores 12.7 mass% of H2. However, H2 desorption reaction occurs over 600 °C due to the large enthalpy change of H2 desorption Ho = 181 kJ/mol H2. The purpose of this work is to control the enthalpy change of LiH to much lower value by a mechanical alloying with Si, where the Li-Si alloy is thermodynamically more stable than Li. The alloy was synthesized from Li granule and Si powder by a mechanical alloying method. The H2 absorption and desorption properties were characterized by High-Pressure Differential Scanning Calorimetry and Thermogravimetry - Differential Thermal Analysis - Mass Spectroscopy, and X-ray diffraction measurement. Pressure - Composition - Isotherm measurements were performed at 400, 450, and 500 °C to estimate the enthalpy change. From the results, it was confirmed that reversible H2 ab/desorption reactions of the Li-Si alloy were expressed as 7LiH + 3Si ↔ (3/7)Li12Si7 + (13/7)LiH + (18/7)H2 ↔ Li7Si3 + (7/2)H2 (theoretically 5.0 mass% H2) at 400 °C. From van’t Hoff plot obtained by the results of PCI measurements, the enthalpy change of the former reaction was estimated to be Ho = 103 kJ/mol H2, which is lower than that of LiH.

  Info
Periodical
Materials Science Forum (Volumes 654-656)
Main Theme
Edited by
Jian-Feng Nie and Allan Morton
Pages
2815-2818
DOI
10.4028/www.scientific.net/MSF.654-656.2815
Citation
K. Doi, S. Hino, H. Miyaoka, T. Ichikawa, Y. Kojima, "Thermodynamic Characterization on Hydrogen Absorption and Desorption Reactions of Lithium – Silicon Alloy", Materials Science Forum, Vols. 654-656, pp. 2815-2818, 2010
Online since
June 2010
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$32.00
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