If they overheat or are damaged, the result can be a fierce, high-temperature fire.

WSJ: Boeing Dreamliner Makes Emergency Landing in Japan

Laboratory tests have shown that such events can prompt nearby cells to quickly heat up and result in a fierce, high-temperature fire engulfing the battery and anything nearby.

WSJ: All Boeing Dreamliners Are Grounded

To make a package out of ceramics you have to fire it, like a clay pot, at an extremely high temperature.

FORBES: It's all in the packaging