MIT engineers produce the world’s longest flexible fiber battery

https://news.mit.edu/2021/fiber-battery-longest-1220

"The rechargeable battery can be woven and washed, and could provide power for fiber-based electronic devices and sensors... might even be used to make 3D-printed batteries in virtually any shape... could also double as structural parts... 140 meters long, to demonstrate that the material can be manufactured to arbitrarily long lengths"