OldnGrounded
There are more than half a dozen litihum ion battery chemistries in fairly common use. All of them, when burning, produce rather copious quantities of hydrogen fluoride and phosporyl fluoride gases in the "smoke." Those gases are significantly toxic.
I have no doubt that battery fires can emit toxic fumes, and that fluorine is particularly nasty.
However I have not seen any evidence that fluorine is present in any commercially available batteries. Could you provide some references for that statement?
Edit: Sorry, my mistake when searching. I looked for fluorine, but the ingredient is fluorophosphate (LiPF6) .