Battery burst into flames after removal!

The attached photos, ( if you can see them) show the destructive power stored in an iPhone 6 battery with approx 70% charge on it. After removing it from the phone, I was straightening it back out, when suddenly it started to flare up ! I had to throw it, it bounced off a door and onto the floor where it continued to burn intensely like a signal flare for what seamed like a 10 seconds or so. This would have destroyed the phone had it gone off while removing it, or seriously burnt my hand for sure in a split second ! Set off the smoke detector, filled the shop with soot and fumes, smelt like a welding shop after, just want to say be very careful with these, I have probably swapped out 100 or more batteries over the last 4 years and never had one go off , now I have a metal can full of water right beside me when doing any iPhone battery swap.