Why Smartphones May Catch Fire: 9 Reasons Why Battery Is At Fault
https://www.indiatimes.com/technology/news/9-reasons-why-smartphones-catch-fire-548144.html

Using a phone with a swollen battery
Using a physically damaged phone
Liquid damage and short circuits
Using fake or incompatible chargers
Using fake batteries
Charging while gaming, calls
Extension cords and power strips
Overcharging
Getting smartphone repaired from unauthorized service centres

8 reasons smartphones can explode (and how to stop that from happening)
https://www.91mobiles.com/hub/smartphone-battery-explode-reasons-how-to-stop/