None of those exploded. If you claim exploded, prove it!
Energy density is still useful for hybrids, especially PHEV. Earlier Prii use a very small lead-acid as 12V battery, but have a very large and heavy NiMH as the main pack. Doubling that weight is not a useful thing.
Telsa battery costs $20k because it goes >200 miles. What cost and weight would these batteries have in that same circumstance? (oh, it doesn't matter because they're only useful for hybrids, so why bring up Tesla?)
Most Priuses still use NiMH (all except the plugin one). In mine, it's around 120lbs, out of about 3200lbs total vehicle weight. Doubling the weight of the battery wouldn't make that much of a difference.
Plugin hybrids and pure electrics need much larger batteries, so it certainly matters there, but for plain hybrids it's not such a big deal.
Though there's certainly a difference, I'm not sure it's all that important here. A fire followed by a mild explosion isn't necessarily that much more dangerous or harmful than a fast fire. You don't really want either.
Energy density is still useful for hybrids, especially PHEV. Earlier Prii use a very small lead-acid as 12V battery, but have a very large and heavy NiMH as the main pack. Doubling that weight is not a useful thing.
Telsa battery costs $20k because it goes >200 miles. What cost and weight would these batteries have in that same circumstance? (oh, it doesn't matter because they're only useful for hybrids, so why bring up Tesla?)