I posted this earlier but I will try again.
Here are 2 different type of dry batteries not in thermal runaway when exposed to water. Halon is known to do the same thing:
YouTube - danger, flames, water and lithium? interested yet?
YouTube - Lithium Ion battery fire
I did find this FAA video which suports what everyone was referring to:
YouTube - Tests on lithium battery fire
It was not a comforting video. I found issues in several areas.
1. most lithium fires to not start under a fire thus the thermal runaway is not as abrupt.
2. They did not show cooling a cell before exploding only after catastrophic failure which much of the energy of the cell is consumed. With a slower process not triggered by a flame, the cells ruptured long before they ignited. Halon or water would ensure their ignition.
3. When the first halon fire extinguisher was sprayed noticed how one of the cells immediately blew.
4. Everything they did seem to keep the fire burning till it was cooled. It was subdued by overkill. Throw enough gas on a fire and it will go out.
5. This seemed to have an aircraft seat and a side wall but it was not in a confined aircraft.
6. They said don't smother the fire which makes sense but they smothered it in ice. If you look at what happen, the fire was out then the batteries began reacting with the water even after cooled to a safe temp!!!!
At the very least the film does nothing to comfort me. This is why I have shown interest in metal containment devices. A trash can can easily be converted on most aircraft to become a metal containment container to close off oxygen and contain smoke. Lithium may not need much oxygen to burn but once they have consumed their batteries, which happens fairly quickly, the only thing left to burn is the platics in the laptop. A well built container with air tight lids will contain this; without near the amount of smoke which was shown on the approve video.
I recognize there is more then one scenario. In an airplane over charge is not as much as a problem as overheat (laptop on lap with blanket blocking fans), and damage.
What I see is people with a blanket on their lap blocking fans overheating laptops. I have done it dozens of times in motels. Mine shuts off, but in the adverse case the batteries start to swell. One may rupture with out a lot of fire or fanfair...to start (unlike the video with the fire driven by another fire below the laptop). At that point you know you have a problem and you get the flight attendant or crews attention.
The crew, already knowing what to do grabs the trashcan, pulls out the trash bag, throws the laptop in the can. The crew grabs the sealable lid and takes the can to the rear of the aircraft nearest the outflow valves. If all goes well, your done! Compare that to the games they were playing in the video, in a confined space. One must realize just how toxic the gas given off is and ...when they do begin to bust how they ignite everything they touch within a 4 foot radius.
But I am no expert....but this is where I would go in testing. I would also test non-halon and non water extinguishing agents. Many have found a pile of sand to nearly contain these kind of battery fires; not that anyone is going to carry 50lbs of sand....but it opens the doors to alternative ideas.