Exploding Headphones Onboard Flight

[fairbasa]

Which is exactly how Boeing overcame the problem with the lithium batteries on the B787. They enclosed them in a case and built a venting mechanism into it.

Lithium Ion batteries don't vent like lead acid batteries...well, unless they've already failed!

The failure mode is thermal runaway induced by a short circuit. This is caused by issues with design, manufacturing or just physical damage incurred in use. Once one cell overheats and can't cool down, it starts a chain reaction until the whole battery goes up.

No doubt the headphone batteries in question were either poorly designed/manufactured (an accident waiting to happen) or were knocked about.