Same ways as with any lithium-ion battery, of any size.
Lithium-ion battery safety 101
In brief — there are two chemicals inside the cell, separated by some kind of thin membrane ( many variations have been tried)
Any number of mistreatments, or simple aging, can cause breaches in that membrane, followed by rapid chemical reaction producing heat and, if there are flames, toxic gases.
Don’t ever throw a bad li-ion cell into ordinary garbage; make sure you know where your local battery recycler is.