By normal conditions I mean charging and discharging and even overcharging if the controller is defective.

Burning the battery is something that I define as not normal conditions.

Many plastics produce toxic fumes when burnt and many such plastics may be used in a car. Burning the battery is not the greatest risk of toxic fumes during a fire. If the fire is intense enough, any released cyanide might also be burned.

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WarmWash 8 hours ago | parent [-]

The battery heats itself in these failure modes.

	▲	adrian_b 6 hours ago \| parent [-]
		Not to 300 Celsius degrees. A battery of any kind can overheat with the output shorted or during excessive overcharging, but normally whenever a battery is used in a device there are protective devices that prevent such events. If there are no protections, the designer is guilty, not the battery. Moreover, such risks are greater for Li-ion batteries, which have flammable electrolyte. Na-ion batteries will replace Li-ion only in certain applications, like stationary energy storage, cars for cold climates and cheaper cars, while Li-ion will remain the choice for maximum energy per kilogram. But it is weird to be concerned about the safety of Na-ion when that is certainly not worse than for Li-ion and most likely it is better.