OT: Kids got an E-scooter?

Electric trains and electric trolley buses seem to manage it.

Putting recharging coils under stretches of road (as is done for some - very few - battery powered buses) does limit the amount of fuel stored in the vehicle.

A lunch box is probably made from very thin steel (or even aluminium), and the flame from a LiPo fire is quite hot, so this might be true.

Those LiPo bags, however, actually work. They have fibreglass layers in them. They are specifically made to not be air tight. That way, the smoke and gases can escape without risk of the bag popping open.

A Li-Ion (including LiPo) cell does not contain metallic lithium, so there will not be a metal fire. It is the volatile components of the electrolyte that burn.

But the vehicle would get progressively heavier as the reaction products built up. I mean, surely no-one would simply dump them to atmosphere?

Good point. The used reactants would be bigger than the fuel, so the waste tank would be bigger and heavier than the fuel tank. It might need a pump to compress the used reactants, which would wreck efficiency.

A fueling station would need big underground tanks for the waste too.

But we could use wind and solar power to reprocess the waste back into fuel and air.