Low-Temperature Synthesis of LiBH4 by Gas-Solid Reaction

The solvent-free synthesis of LiBH4 from LiH in a borane atmosphere at 120 degrees C and ambient pressures is demonstrated. The Source of borane is a milled LiBH4/ZnCl2 mixture, in which Zn(BH4)(2) is generated by a metathesis reaction. The yield of the reaction of about 74% LiBH4 shows that a bulk reaction is taking place upon borane absorption by LiH. This indicates that the formation of B-H bonds is the limiting step for the formation of LiBH4 from the elements. Therefore, the use of diborane as a starting reactant allows one to circumvent the reaction harrier for the B-B bond dissociation and explains the rather moderate synthesis conditions.