If we're talking about mining lithium from elsewhere in the solar system or even galaxy, I'm willing to be that fusing hydrogen and helium to get there is a muc

If we're talking about mining lithium from elsewhere in the solar system or even galaxy, I'm willing to be that fusing hydrogen and helium to get there is a much more energy efficient route. Maybe this is something you do where you don't need as dense a form of energy, but still. It's only the 3rd element. Rare earth metal mining in the asteroid belt is the one most likely to be necessary.