[aksss]

I recall Vaclav Smil saying batteries are consistently about 2-3% per year over the long haul. It's not a Moore's law scenario, but a very slow crawl. "Miracles might happen," he says, "but would I bet on a miracle happening? No."

This link is to the point in the video where he says this, but the whole talk is quite interesting. https://youtu.be/gkj_91IJVBk?t=1705

Edit: here's a more recent video of Smil talking about energy density of batteries and the problems there, specifically mentioning the unlikelihood of flying on battery anytime soon. https://www.youtube.com/watch?v=91Cs-ZkAjCg