If the amount of oxygen exchanged between the battery and atmosphere is enough to make the battery "much lighter" in its charged/non-oxygenated state, wow, that

If the amount of oxygen exchanged between the battery and atmosphere is enough to make the battery "much lighter" in its charged/non-oxygenated state, wow, that's got to be a lot of oxygen! I didn't see any numbers in the article, but a commenter (name, moishep) on the site posted the relative atomic masses of the elements and compounds involved: Li ~7, O ~16, LiO2 ~39 If someone with a better understanding of the chemistry could answer, does this mean that a discharged battery would have over five times the mass of a charged one? And if that much oxygen is being released in the charging process, that's quite a fire hazard that will need to be designed around. Or am I missing part of the physics/chemistry involved?