LITHIUM BOROHYDRIDE AS A HYDROGEN STORAGE MATERIAL: A REVIEW

Abstract

The major obstacle in transition to the hydrogen economy is the problem of onboard hydrogen storage. Solid-state hydrogen storage is the safest and most efficient method for hydrogen storage. Most of the metal hydrides exhibit very large volumetric storage density but less than 5 wt % gravimetric hydrogen density. Light metals such as Al, B bind with four hydrogen atoms and form together with an alkali metal an ionic or partially covalent compound called complex hydride. LiBH4 is a complex hydride with 18.5 mass % gravimetric hydrogen density and 121 kg/m3 volumetric hydrogen storage capacity. The desorption temperature of LiBH4 is greater than 470°C, thus making it difficult to use for storage applications. In addition, the conditions for reversible reaction are unfavorable. Modification of thermodynamics of the hydrogenation and dehydrogenation reaction is possible by using additives which could destabilize LiBH4 by stabilizing the dehydrogenated state. This could decrease the heat of reaction and reduce the desorption temperature at the same time, making the conditions for reversible reaction more optimum. Several additives which could destabilize LiBH4 have been reviewed.