what are the differences between an iPhone battery and an iPad battery?

Hi. As the subject line may say, I’m interested in knowing as specifically and as detailed as possible what are the differences between the battery for a iPhone SE first generation made in 2016 and an iPad mini?

I use both devices basically the same but I noticed big differences in how the batteries last. Any information could be provided and nitty-gritty details would be appreciated.

thank you for your help.