Investigation of the dehydrogenation behavior of the 2LiBH_4:CaNi_5 multicomponent hydride system

摘要

LiBH_4 has gained much attention as a potential hydrogen storage material due to its high hydrogen storage capacity of 18.5 wt%. However, LiBH_4 only releases its full hydrogen capacity at temperatures greater than 600 ℃ 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 ℃, making them less desirable for automotive applications. In this work we report the solid-state decomposition of LiBH_4 in the 2LiBH_4:CaNi_5 system below the LiBH_4 melting temperature of 270 ℃. In situ neutron diffraction measurements confirmed the decomposition took place in the solid state at 200 ℃, forming LiD, CaD_2, Ni_3B and Ni_2B phases as end products. The solid-state decomposition was further supported by SEM and TEM measurements showing the presence of nano-crystalline particles.