This has nothing to do with the battery. The claim is that they have solid intelligence that someone is trying to fit a bomb inside a laptop/tablet and it would be hard for screeners to tell the difference between legitimate devices and bombs.

However, aviation experts have weighed in and stated that even a full pound of pure explosives detonated in the cabin of a modern airliner is unlikely to bring the plane down. So you could just ban very heavy laptops and leave the rest alone.

You know what HAS brought two 747s down in the last decade? Lithium battery fires in the hold. UPS and FedEx no longer permit bulk shipments of L-Ion batteries by air because of the risk. So they want to move devices from the cabin (where if they catch fire someone will notice and they can be dealt with) and put them all together in the hold where fires are harder to detect and impossible to fight!

Smart, so smart!