Battery tech is a big stumbling black for all green energy technologies. Its a stumbling block for geen power soruces because they are mostly intermittent and need to store most of their energy to be useful. Its a stumbling block for electric vehicles because gasoline is just that much more mass efficient than batteries. Its a stumbling block for hydrogen power... because hydrogen power is just an exotic and inefficient battery.
everything cool and awsome that we want is being held back by shitty batteries.
Your hover board? Shit batteries.
That sick cyborg arm shit batteries.
That cool lazer gun you want shit batteries
The future is here, the tech is here but its batteries required and the batteries are shit.