Nice work guessing, but if you combine the uncharged ion battery with the battery charger and resupply the gun with it, it will break open the safe and reveal a book explaining not only how to make a bomb, but it has a large quantity of lore as well. Unfortunately, I was not very clear that you had to put the charged one back in, so that's on me. Still though, you guessed, and you lived. Congrats!