In this case though it is a little interesting, because it isn't really "storage" in the normal sense. It is more about how to maximize volume/weight and then be able to empty it out, like a jug of water, all at once.

Though, I suppose you could go more classic and just have two sets of batteries and you swap them with each shipment. Deliver full batteries and return the empties to get refilled.

The whole great battery race though is really interesting. Hopefully, eventually, some of the more fantastical claims will start bearing fruit outside of a lab. =)