Microstructural change of 2LiBH(4)/Al with hydrogen sorption cycling: Separation of Al and B

Abstract

Using transmission electron microscopy, microstructures of 2LiBH(4)/Al are investigated during the hydrogen cycling (2LiBH(4) + Al <-> 2LiH + AlB2 + 3H(2)). Mechanically, ball milled 2LiH/AlB2 mixture shows a homogeneous phase distribution. For the hydrogen absorption, the decomposition of AlB2 and the formation of 2LiBH(4) occur simultaneously. During the hydrogen cycling, the incomplete formation of AlB2 results in a spatial separation of Al and B. A lack of reactive B from AlB2 results in a limited formation of LiBH4, which leads to the capacity loss of the system. (C) 2009 Published by Elsevier Ltd. on behalf of Acta Materialia Inc.