[twoslide]

That's a good point, although I am not sure whether the "six times" claim was based on the first cycle or the subsequent cycles (partly because the authors didn't make it themselves). Even if subsequent cycles are 1/3 as the first, that could still mean twice as much charge as li-ion.

[oliwarner]

But with materials you can extract from seawater (with the valuable by-product of potable water).

All other things being equal (unlikely to begin with), these would be furiously cheaper to make, and wrest production from China.

Even at half the performance of lithium, this would look tempting.