The 300-meter-long cruise ship AIDAperla receives in 2020 a battery pack capable of generating a total output of 10 MWh. As of today this will be the largest battery storage system worldwide to be ever installed on a passenger ship.
A few questions remain like the rather short typical estimated life of a Lithium-Ion battery of about two to three years or 300 to 500 charge cycles, whichever occurs first. IMO the replacement will be a very costly affair, unless the possible savings will allow this. Time will tell.
I donot know how safe these batteries are but you should not think what could happen in case of a short circuit.