Lithium batteries immediately burst into flames if their guts get exposed to oxygen. Not candle flames either, road flare flames. Think about that the next time you sleep with your phone next to your pillow. To illustrate that point, the folks at Experiment at Home have put a variety of batteries in a hydraulic press so you don't have to! The video starts with some bland AAs, but the fire really starts buring when they switch to the LiPo batteries around the 2:20 minute mark.