Investigation of the dehydrogenation behavior of the 2LiBH4:CaNi5 multicomponent hydride system

Abstract

LiBH4 has gained much attention as a potential hydrogen storage material due to its high hydrogen storage capacity of 18.5 wt%. However, LiBH4 only releases its full hydrogen capacity at temperatures greater than 600 °C and requires hydrogen pressures of at least 350 bar to rehydrogenate the end products. The dehydrogenation temperature can be altered by thermodynamic tuning through the addition of a reactive agent resulting in a lower enthalpy of dehydrogenation. Most multicomponent hydride systems display dehydrogenation temperatures above 300 °C, making them less desirable for automotive applications. In this work we report the solid-state decomposition of LiBH4 in the 2LiBH4:CaNi5 system below the LiBH4 melting temperature of 270 °C. In situ neutron diffraction measurements confirmed the decomposition took place in the solid state at 200 °C, forming LiD, CaD2, Ni3B and Ni2B phases as end products. The solid-state decomposition was further supported by SEM and TEM measurements showing the presence of nano-crystalline particles.