Is it true that lithium-ion batteries explode because of heat?

Lithium-ion batteries don't explode just because of heat, it's more nuanced than that. Heat speeds up the chemical reactions inside them, but it's mainly when there's a short circuit or overcharging that things get dangerous - that's when they can catch fire or explode. Manufacturers put safety systems in place to prevent that, but a damaged or defective battery still poses a risk, especially if it overheats at the same time.