Lithium batts in laptops, cameras, etc. are usually manufactured in plastic casings. The generic RC lipos used in RC aircraft and most lightweight platforms use lipos with the cells exposed. The cells are encased in something similar to a potatoe chip bag, or mylar. It's thin and easily punctured if a sharp wheel on a hand carry bag is smushed into it, for example. If punctured expect lots of smoke and likely sparks and flames. That's why the packing of lipos is so critically important, whether it's hundreds of pounds of lipos or just a single lipo pack strapped to a quadcopter.