EVs in general aren't old enough to have old-vehicle-fire issues yet, very much. And absent a serious collision, their main exposure to a battery issue that's not due to a manufacturing defect is from road hazards. Tesla had several fires related to underbody damage causing battery penetration early on, and added skid plates and redesigned battery cases to mitigate that. Arguably, those were collision related, though there was little the driver could do to avoid them.

In theory, a Li battery can develop dendrites over time that eventually short-circuit the battery. Again, EVs haven't been around long enough to see whether that's happening, and avoiding that is a major effort in battery design. The heat a short can light off the flammable electrolyte in the most popular Li battery chemistries, and the resulting fire really can't be put out; all the FD can usually do is protect the surroundings and let the car melt down. If enough water is available, they might be able to cool things down and the fire may stop ... for a while ... possibly reigniting in the salvage yard. LiFePhosphate batteries are preferred for trucking and buses for several reasons, and one of them is that they don't have the flammable electrolyte of the more common car batteries; they also hold less charge, unfortunately, and are heavier. Luckily, the batteries don't really explode like gasoline; the cars give the occupants warning if something happens while they're driving. Main issue is what happens when they're locked up somewhere unmonitored, and a few have resulted in serious building damage. In a way, they're like diesel: once they start burning, they're difficult to put out and liberate a lot of heat.