Microstructural change of 2LiBH4/Al with hydrogen sorption cycling: Separation of Al and B

Using transmission electron microscopy, microstructures of 2LiBH4/Al are investigated during the hydrogen cycling (2LiBH4 + Al ↔ 2LiH + AlB2 + 3H2). Mechanically, ball milled 2LiH/AlB2 mixture shows a homogeneous phase distribution. For the hydrogen absorption, the decomposition of AlB2 and the formation of 2LiBH4 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.