Magnesium borohydride (Mg(BH(4))(2)) is a promising material for hydrogen storage because of its high gravimetric storage density (15.0 mass%). We intended to synthesize Mg(BH(4))(2) by decomposition reaction of LiBH(4) with MgCl(2) by heat treatment without using a solvent, where the product consists of LiCl and a compound of magnesium, boron and hydrogen. Hydrogen desorption temperature of the product is approximately 100 K lower than that of LiBH(4) and the decomposition consists of a two-step reaction. The products of the 1st and 2nd decomposition reactions are MgH(2) and Mg, respectively. This result indicates the following two-step reaction (1st reaction: Mg(BH(4))(2) --> MgH(2) + 2B + 3H(2), 2nd reaction: MgH(2) --> Mg + H(2)). The first decomposition peak is dominant and is around 563 K. The 2nd decomposition occurs at the temperature greater than 590 K. (C) 2007 Elsevier Ltd. All rights reserved.