Spicy pillows are lithium-ion batteries from common devices (phones, tablets, laptops sometimes, even headphones) where the battery has chemically deteriorated over the years until it starts to swell up and expand its housing. Most LiOn batteries are actually just black plastic sheaths over the working parts, so the battery swells up like a pillow. Apparently batteries in this state are a severe fire hazard and LiOn batteries burn extremely hot.

The spicy pillow happens all of the time, and it has likely happened on almost every older device that you own over time. I have a few devices > 10 years old that haven't had this deterioration but most devices will have this happen.

Educational article: https://www.ufinebattery.com/blog/spicy-pillows-uncovered-everything-about-swollen-battery/

I had older Moto G7 Power phone that developed a spicy pillow. The clue was that I couldn't fit the phone into its case anymore, and then I realized that the phone was basically convex on the bottom instead of flat. Ruh-roh.

I replaced the battery with a cheap kit from Amazon (charges like new). Replacing a cell phone battery on a smart phone is fussy and destructive (you have to slit the glue seam in most phone cases to get the phone apart but OTOH there are a plethora of how-to videos online on the procedure for most phones.)

I harvested the bad battery and placed it on top of wood scraps in a burn barrel in our yard and set the wood on fire. When the fire finally penetrated the battery, there was a whooshing sound and for about 15 seconds it looked like someone was aiming a torch up from the fire. For a small object about 1/8 inch thick and 3 inches square it burned pretty hot.

So, please, from a first hand eye witness, respect the nastiness of spicy pillows. I don't think you are supposed to trash them... Supposedly take them to some retailer who has a battery drop off, like the "Batteries Plus" chain, and they will recycle them for free.

Or, if you are a polluting asshole like me and no neighbors know or care, burn it in the backyard in a container and dump the cold ashes into your trash. Stand back and don't breath the toxic smoke.

Anyway... the inventor of the cathode technology for LiOn batteries was... drum roll....

https://en.wikipedia.org/wiki/John_B._Goodenough

John B. Goodenough

There's a viral video of some poor Chinese guy carrying his e-bike battery onto an elevator in his apartment building. There's the view inside the elevator cab after he gets on where the battery ignites. Suddenly the video just goes black with smoke and flames and the guy is trapped between floors with this going on. Cut to the EMS arriving at the elevator and pulling the guy out, who is basically immolated.

Yes, plenty Goodenough.