As long as the battery doesn’t break, like a laptop battery should not break open. They should be okay. I mean really, our navy has submarines powered by a nuclear reactor. Did you think about that?!!! I wonder what recharge mechanism the submarines have.
Solar.
Diesel powered subs (discounting aip and others) have always depended on running the diesel (while snorkeling) to recharge the main batteries. Same mode proposed here. Just a much more sophisticated storage battery installation with larger recharge requirements. Larger diesel with larger air intake requirement. A heck of an advance if it can be done safely. Diesel boats right now are so quiet (snorkeling or submerged in battery mode)that this advance narrows the old diesel vs nuke boat debate.
Who knows, this might end any rationale for nukes at some point in the future with continued improvement.