LiAlH4 would be one of the very few credible compounds improving performance a little bit over Rp-1 (~kerosene) or solid fuels in rocket engines... IF:
- It could be made SAFE in 100t amounts: no detonation, no easy ignition etc etc
- It could be pumped somehow, for instance as a slurry in kerosene (for liquid engines)
- It were reasonably insensitive to humidity
- It remained stable when polybutadiene polymerizes (for hybrid engines)
mixed with aluminium perchlorate additionally (for solid engines)
- It were affordable
One path might be to encapsulate fine powder in thin aluminium. This has been tried with AlH3, but LiAlH4 looks preferable.
LiBH4 is too toxic and expensive, probably no option.