I'm wondering the same! I have an old Android tablet that just boot-loops and has a swollen battery. I'd like to get rid of it but not sure how to wipe it first!
Break it open and shred the Mainboard.
If you can still open the recovery menu, you could wipe it from there. Otherwise, you should probably destroy the device/memory.
if I could pinpoint the eMMC I could just drill a hole in it