Scientists in Canada and France have created a micro-supercapacitor with the same energy density of a modern lithium-ion battery that could potentially last forever. Supercapacitors have long been eyed by scientists and industry leaders like Elon Musk as a replacement for batteries, since they can be recharged nearly infinitely without a loss of capacity. The research does have a "small" catch, though. The capacitor's porous cathode is just a few square millimeters in size, because it's built out of exotic materials like gold and ruthenium oxyde. If it can be scaled up, however, it may lead to capacitors with the same energy density as existing batteries, much lower charging times and longer lifespans.