You don't need modern lithium batteries to start a fire.
Many years ago,when I was but a stripling lad,I worked at an Electronics/Electrical store.
In the Electronics section we had what used to be called a "tea chest"( a plywood crate that tea was shipped in) for a waste bin.
All sorts of junk,including shredded paper,flat batteries,etc were chucked into this thing,& dumped every couple of days.
On this occasion,the Electrical Dept received a bunch of warranty return Lantern batteries back,& after checking them with a battery tester,they were dumped-----in our bin,as theirs was full.
Sometime later,I noticed a burning smell,& on closer inspection,a small stream of smoke emanating from our bin!
We dumped everything out on the floor,stomped on anything burning,then found the source,-------two Lantern batteries with the contact springs tangled so that the +ve terminal on one contacted the -ve on the other,& vice versa.
The "dead" batteries still had enough "grunt" to make the terminals extremely hot.
This caused the shredded paper to smoulder,& hence the smoke.
Luckily,this all happened mid morning,& not at closing time,as we probably wouldn't have had a job to come to the next morning!
I have since tried this trick with "flat" 9volt batteries (the little ones we all use ).They too,will get seriously hot!
If ever I dump Batteries,I make sure I put some tape across the terminals.
Of course, we are not supposed to dump them any more,so I guess that takes the problem away from me & gives it to the recycling people.
VK6ZGO