Cyberpunk

This - once we've got small, dense power storage we can do all the cool scifi stuff: man-portable lasers/coilguns, strong augmentics with long battery life, chainswords, autonomous robots that operate for long spans of time.

I saw something once that said when you're writing scifi to pick one technology to improve/add, and have all the changes in the setting flow from that. I almost always pick batteries.

In a cyberpunk setting, I feel like the new tech should be stuff that demonstrates the wealth disparity, being used everywhere, wastefully in rich people's domain, while regular people are dependant on clunky, heavy, maybe unsafe older stuff. Batteries could be a good one for that, easy to build a plot around people stealing the new batteries from advertising drones or electric scooters from uplevel and selling them to shops that retrofit them into augmentic limbs or robots who otherwise need to recharge every couple hours.