Batteries store the bulk of the electrical energy that powers electric vehicles today, but they’re limited by how quickly they wear out. Batteries are helped along by capacitors--electrical devices that charge up and drain quickly and can be recharged over and over again, but hold comparatively much less charge. So for some years now, the hunt’s been on for an ideal crossbreed of batteries and capacitors--an electrical device that will store a lot of charge, like a deep bowl of soup, but is also swift to fill up and drain. Scientists found it--they just had to break a few eggs.
That’s because, it turns out, chicken eggshells may offer a solution. A group of Canadian scientists have tested and shown that the membranes from eggshells, toasted to 800 degrees, make for surprisingly efficient supercapacitors that could one day be used in electric vehicles, maybe even in cell phone and laptops.
"What we were able to achieve is [a capacitor] that looks a lot more battery-esque," said David Mitlin, the lead on the eggs-periment. "What we showed is our material can hold three times as much charge as activated carbon but last just as long." That’s three to four times as much charge as a commercial electrode. And, unlike expensive carbon nanotubes and graphene sheets that are also being turned into capacitors, eggshells are usually thrown away as trash. "People will actually pay us to take them away." Mitlin says.
It has to do with the atomic and microstructure of the heated eggshell membranes. The membrane’s chock full of nitrogen groups which can soak up and store extra charge. Plus, the interconnected mesh of carbon fibers make for a great conducting highway, letting the charge flow in and out of the capacitor rapidly.
Oddly enough, other chicken bits have been found to be suited to the task of energy storage. A little over years ago, scientists at the University of Delaware discovered that roasted chicken feathers made great hydrogen storage materials for fuel cells, again, because of their unique porous micro architecture.
Mitlin’s group has plans to develop their discovery towards commercial application. After all, high storage capacitors in our electronics could make a world of difference to our daily lives. "If your cell phone ran on a capacitor you could charge it in 45 seconds," Mitlin says. Just make sure your capacitor is cage free.