Decomposition and formation of magnesium borohydride

•Polymorphism of magnesium borohydride is described.•The mechanism of decomposition strongly depends on the conditions.•Different syntheses of magnesium borohydride are summarized.•Nanoconfinement is found as a promising method for reversibility.•Application of magnesium borohydride in fuel cell and secondary battery is started.

Nowadays, among all known borohydrides magnesium borohydride, Mg(BH4)2, is the only one that demonstrates a partial reversible hydrogen sorption in moderate conditions. This is a clear reason why composites based on Mg(BH4)2 are extensively studied fundamentally and are applicable as hydrogen storage materials. The review summarizes the main challenges still present for Mg(BH4)2 that are decomposition and formation providing for the practical use of hydrogen mobility. Some technological approaches to the development of nanocomposites based on Mg(BH4)2 are considered and discussed. Profound conclusions and future application of nanocomposites in fuel cells and secondary batteries is the final item of the proposed work.

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