Why do you say that if it's 3x the energy density per volume and "only" 2.5x heavier? That should give it at the same volume as Li-Ion 82.5% of the weight.

I agree this doesn't solve the weight problem for EVs, except only a little it seems, but if these batteries can be made competitive on price with Li-Ion (Eventually), and unless we find a much better alternative weight-wise, then this sort of battery would still be very useful for EVs because of the safety they give.