"Tesla's /cells/ are also "fundamentally unsafe", but they make the /batteries/ as safe as possible."

While it's certainly true that the Li-ion chemistry used in the Tesla's batteries are flammable, keep in mind the current common alternative to those potentially burning cells is carrying round a metal or plastic tank with 10 or more gallons of gasoline in it. If there weren't a 100+ year history of people doing just that and getting away with it most of the time, you surely wouldn't be allowed to do it in today's safety-conscious society.

Gasoline is not all that dangerous in the vast majority of failure modes. Li-ion is both corrosive and easier to set on fire which is a real issue for hybrids and aircraft.

Vast majority, yes. But I've seen failure modes where it was dangerous on more than one occasion.

Gasoline isn't dangerous? It's ten times as easy to light up a gas tank than a battery pack, and the energy release is instant.

You can drop a lit match into a bucket of gasoline. It needs to be aerosolized to be explosive.

You can indeed, and it ignites the gasoline. Gasoline vapors in air have relatively wide explosive limits which can be attained in a wide variety of ways, not only by aerosolization.

Then the multiple times I've seen that done, by multiple different people, all happened with something other than gasoline.

I'm not saying it can't happen, and I'm well aware that gasoline vapors are extremely dangerous. I'm just saying that the gas tank in your car isn't "10 times as easy to light up" as the newer, super-energy-dense lithium chemistry based batteries.

Diesel fuel and kerosene are good candidates for the "something other than gasoline". They'll both happily put out a lit match.

May I suggest, by the way, that you think twice and double-check your facts before posting potentially fatal fire-safety advice on the internet? You'll probably never know if you've killed somebody. If you want to try the gasoline-bucket experiment, I recommend doing it in a small coffee can on a large concrete pad that you don't mind discoloring.

I think the critical difference is how long the bucket full of gasoline has been sitting there. If you just filled it up, there will be a lot of vapors hovering above the surface. If it's been sitting, undisturbed and uncovered, for a good long while, there won't.

In the former case, you're going to lose your eyebrows, at best. In the latter, the match will go out.

Gasoline vapors are several times heavier than air, so they tend to stay in buckets, crawl across basement floors, and so on. Maybe if you let the bucket sit there long enough, they'll displace enough oxygen that you won't get a fire at the surface.

Another crucial variable is the temperature. If you do the experiment with the bucket sitting in a snowdrift, you probably can get it to snuff out a match, regardless of how long it's been sitting there.

Yup, it works out fine almost every time.