Li-ion batteries store high quantities of energy in form of Chemical-electrical energy... chemically speaking, they can become '''unstable '''due to a number of factors, get more info here:
It is best to take care of your batteries and buy only from established battery manufacturers (they have better manufacturing process and stricter Quality control). Watch out for bloated batteries as they indicate some unwanted reactions inside (bloating due to gas production)
Li-ion batteries store high quantities of energy in form of Chemical-electrical energy... chemically speaking, they can become '''unstable '''due to a number of factors, get more info here:
https://www.livescience.com/50643-watch-lithium-battery-explode.html