Electric Vehicles

There may also be some energy released from the battery materials themselves burning (like, an uncharged battery might have a significant amount of energy to release when combusting)

No, it's not and you probably intuitively know this already, but an uncharged battery burns almost exactly the same as a charged one.

Here is a other way to think about it. Let's trade "gallons of gas" for "bowling ball at the top of the slide" both object represent an amount of stored potential energy.

Let's arbitrarily say that you gallon of gas is equivalent to a bowling ball sitting on top of a 1ft tall slide. The gas tank is the equivalent of a ball sitting on top of an 18ft tall slide, and the battery is roughly a 3ft tall slide. If someone asked you which slide had more potential energy, you might say "the gas one", but what we have missed is that the gas slide was built at sea level, and the battery slide is sitting on top of a mountain. Normally, that whole mountain's height isn't considered in the potential energy of the ball on the slide, but the battery fire is a catastrophic event where the ball flies off the end of the slide and falls down the side of the mountain.

Basically, the battery has a ton of potential chemical energy in it, which is used to store a little bit of electrical potential.