My immediate thought is, why not store it as peroxide? It takes more energy to make too, but at least it's liquid rocket fuel instead of gaseous rocket fuel.
> Efficiency Admittedly, the current, non-optimized, technical trial-level efficiency of the here-built system was very low, with an overall storage efficiency of 11.4%,
So far their is even lower, though they claim a theoretical max of 79%. Storing large amounts of energy that's ready to be used is rarely not dangerous in any case. Except maybe potential energy of a tank of water on a mountain.