Answer: Lithium metal batteries burn spontaneously when broken apart.
Step-by-step explanation:
Most Lithium-Ion batteries have an electrolyte that is flammable. If they have a manufacturing defect they can short internally and suffer a runaway event, heating up and bursting and the electrolyte ignites and burns.
Otherwise, most Lithium batteries have a built in protection circuit that prevents overheating from external shorts or near shorts or overcharging.