A japanese startup is working on a (surprisingly small) battery energy "tanker":

https://power-x.jp/en/newsroom/Introducing-the-world%E2%80%9...

I think there are some startups working on cargo train "tankers" in the US too.

An idea I had after seeing the tanker concept was to have the battery carrier also serve as a generator via wind power. If its a huge ship I suppose you could just stick a turbine on it and go where the wind is blowing. I think a more fun concept is generating power off of a smaller scale cat- or trimaran generating both propulsion and power by sailing conventionally.