Becoming a spicy pillow is the inevitable fate of almost all small lithium electronics batteries. Keeping them in the 60-80% range will slightly help extend life, but that's about it, unfortunately.
Free version: https://github.com/davidwernhart/AlDente-Charge-Limiter
Pro version: https://apphousekitchen.com/
British English speaker here. I've not come across that expression before. The "pillow" part seems obvious, but not "spicy". What am I missing?