Oof, sorry to hear that. And yeah I think folks in the Leaf subreddit were calling them "crocodile" cells/packs, and I'm completely blanking on the internal name, only vaguely remembering one translation as 'high heat' which was incorporated into the warranty packs and the cell upgrades in 2015 for the 40kWh "HC1" version.

And yeah, originals were 24kWh and there's no getting around that being just for short commutes. I'm assuming at this point on the newest models, that they're beyond the 63kWh, but those did have a different pack design. The 40s would absolutely physically fit on an older leaf, but the battery controller wouldn't be compatible with the computer without 3rd party changes, though I'm sure people have done that and probably more by now.