Was the exploding cellphone actually a home-made bomb?

New Express interviewed an expert on battery technology, Mr. Cai, who said it was unlikely that a cellphone battery would explode under those circumstances:

r Cai said that although exploding cell phone battery incidents happen from time to time, most of them happen during charging or when the phone is used for a long period and becomes hot. But this time this man had not charged the phone or used it for an extended period. Also, the shop he works in is warm in the winter and cool in the summer and doesn't possess any conditions that might cause an explosion.

Mr Cai said currently the majority of cell phones use lithium batteries and the direct reason for a lithium battery to explode is if it gets too hot and expands. Mr Cai said, "There are many reasons that a battery could overheat. Charging or long use can easily cause the battery to overheat, and this is produced by a chemical reaction. Additionally, warm environments can cause batteries to get too hot, so lithium battery instructions all warn 'do not place the battery in a warm environment or throw on fire'."

Mr Cai said all media reports said that the man put the phone in his pocket and was not using it. Also the location of the incident was not a high temperature place, therefore the likelihood that the battery could explode is very small, "unless there is some outside danger that caused the battery to explode."

While we can all breath a sigh of relief and return to using our cellphones without fear, these reports bring up more questions than answers. What in the world was someone doing with an explosive in their chest pocket in the first place?