Its not the Lithium that is a problem. Its the Colbolt-59 that's next to it. A typical Tesla has about 15 pounds of Colbolt-59. If a small tactical weapon would be used near the location of a single parked Tesla, the Colbolt-59 will transmute to Colbolt-60, the deadlist substance known to earth. 15 pounds of Colbolt-60 is enough to kill 24 million people. Imagine a parking lot of them. 4 tons of it is enough to annihilate all life on earth. These Tesla cars are the biggest extensional threat to human kind. Anyway, have a nice day!
The entire cross section of a Cobalt 59 atom is only about a barn. Since a nuclear weapons dispersion of neutrons is in three dimensions and therefore the concentration of neutrons drops quite quickly as a measure of distance the car will have to be uncomfortably close to transmute a meaningful amount of Cobalt 60.
Since this phenomena is very much geographically constrained by the properties and physics of the blast, using over the top comparison of "15 pounds could kill 24 million people" should instead read "15 pounds generated from 240,000 micronuclear explosions generating this material near 100 people each could kill 24 million people if they decide to linger near the Cobalt 60 on the order of years due to its long half life".
Edit: It is important to understand the underlying physics to make an accurate characterization of the risks involved. Cobalt 60 is not the most deadly substance to humans; I would argue alcohol is higher than Cobalt 60.
Nuclear wars would mostly involve thermonuclear weapons detonating high enough up that their neutron flux will essentially dissipate before reaching the ground where all the cars are. That will maximize the area destroyed by the shock wave.
It's true that a neutron bomb used tactically against ground targets could transmute car batteries. But those would tend to be used in the countryside against armor formation rolling through rather than against cities where all the cars are. And they have a fairly small radius of effect anyways.
EDIT: And in any event, I'm sure that the transmuted cobalt will be the least of our problems if it ever becomes relevant.
This is probably based on the idea of Cobalt bombs (https://en.wikipedia.org/wiki/Cobalt_bomb) intended to make areas uninhabitable due to radiation. But in that case the Cobalt 59 is placed directly around the nuclear bomb, and spread across the area by the explosion.
It doesn't seem plausible to me that this would be a real danger. If I'm close enough to a nuclear explosion that can affect the Cobalt-59 in my car, I'm probably vaporized anyway.
