Batteries catch fire. Very large ones, or many cells together can mean a very hot, very dangerous fire, with the occasional violence of a cell bursting.

Being in close contact with something like a phone when that happens would cause burns, but they don’t “explode” with very much force. (Relatively speaking. You wouldn’t get lethal fragmentation for example, I don’t think)

The note 7 batteries didn’t really go boom in the way an actual explosive does, though the reaction is a sudden and fast release of thermal energy, its not that much energy in terms of explosive devices.

So no. You can’t “hack” a phone and turn it into a bomb using just the hardware that is already inside. You could start a fire, and that could be deadly, but as an explosive device the battery in most phones is not that potent.