Why the fixation with Lithium?
Why is there such a fixation with Lithium? Does it really matter what battery technology is used provided it works reliably and does not burst into flames at random intervals?
Suspect that in something weighing over half a million pounds they could have used lead acid (ancient, reliable, tried, tested and not prone to catching fire) in which case Dreamliners might still be in service. Not that I'm suggesting this would be the best choice but it does illustrate the point.
If every Lithium battery is to be attended by a large tank of water the weight advantages will soon disappear.