So, as someone who's actively thinking about what our future looks like because I'm getting ready to write a speculative fiction novel, this is something I'd thought about as a potential solution, and it's interesting to look at the ways in which people are starting to work around fossil fuel without batteries.
Oouu, biopunk. will check out, for sure, if only to see what he thinks about energy storage. Flywheels, gravity batteries, springs, it's all interesting but none of them solve the problem as effectively as chemical batteries do. I could create some sort of magic to do it, but I'd rather see what I can extrapolate from first.
"Flywheels" made me think of an interesting test that was done with city buses in Germany, I think. A giant flywheel was mounted horizontally under the floorboards of the bus, and "charged up" when the bus was in motion. As the bus pulled away from each stop, it used the stored power of the spinning flywheel to do the hard work of getting the bus up to speed. Which allowed the bus to have a tiny engine (like a 3-cylinder, or something crazy like that!), and still carry a full load of passengers. Of course, a spinning flywheel has a LOT of potential energy stored, and any little problem can cause them to come apart, and destroy everything around them. So they developed a flywheel that was entirely spun of fiber (maybe carbon fiber? kevlar? can't recall), so if anything went wrong, the whole thing instantly turned itself into a giant ball of fluff! All the potential energy was released in one massive discombobulation that resulted in a cavity full of cotton candy, rather than pieces of metal flying everywhere in the cabin of the bus. I assume this didn't work out in the end, because I heard of this maybe 20 years ago? And haven't heard peep of it since then.
So, Baader-Meinhoff, I just saw a video on this the other day, maybe even yesterday. They were also used in the Phillipines. I think the idea was ... "fine"? But not good enough to keep improving as the cost of gas was cheap. Definitely something swipeable for future-tech.