It’s not the lithium which is dangerous with li-ion batteries though. It’s the flammable liquid electrolyte. That’s what gives you explosions and fire. I think the lithium does make it harder to put out after it has caught fire though, but it’s not generally the reason why they catch fire.

With next generation batteries, some have been shown to be completely fire proof, as they don’t all use the same flammable electrolyte as Li-ion. With some, you can cut them in two without anything happening.

I’m not at all worried about the lithium in lithium metal batteries. The key is reaction rate. A pure chunk of lithium metal can be dangerous because all the metal is available for reacting to happen nearly instantly. A microsopically thin slice sandwich between non-reactive materials is not a big concern. With catastrophic damage you may have thermal run-away. But fire departments in countries with high share of EVs, like Norway, have already shown they can handle it well, and they consider EVs far safer than gasoline cars.