It just dawned on me that you can simply store positively and negatively charged particles separately (e.g., electrons and protons), just like cells do, to generate a difference in electrostatic charge, and therefore motion / electricity. I’m fairly confident space near Earth, is filled with charged particles, since my understanding is that the atmosphere is our primary defense against charged particles, and the source of the Aurora Borealis. So, by logical implication, you can collect and separate positively and negatively charged particles in space, bring them back down to Earth, and you have a battery. Moreover, because it’s subatomic particles, and not compounds, you have no chemical degradation, since you’re dealing with basically perfectly stable particles. As a consequence, you should be able to reverse the process indefinitely, assuming the battery is utilized by causing the electrons / protons to cross a wire and commingle. Said otherwise, there’s no reason why we can’t separate them again, producing yet another battery, repeating this indefinitely. I’m not an engineer, and so I don’t know the costs, but this is plainly clean energy, and given what a mess we’ve made of this place, I’m pretty sure any increased costs would be justified. Just an off the cuff idea, a negatively charged fluid could be poured into the commingled chambers, and drained, which should cause the protons to follow the fluid out, separating the electrons from the protons again.