There's hope that sodium-ion tech will come to the rescue, here. The energy-density is bordering on 'good enough' but it's not quite there, yet.

There's other technologies that they're trialing for boats that seem silly but works on paper at least. We're currently building a ferry with a massive flywheel to store lots of rotational inertia to convert to electricity, which on the face of it is bonkers but again, the maths says it's good.

Almost as bad as a fuel oil fire on a cruise ship.