Can I interest you in a microbattery with a power density better than the best supercapacitors—2000 times higher than other microbatteries—and energy density rivaling conventional lithium-ion batteries? Yes? Thought so.
A team of researchers at the University of Illinois report on a Li-ion microbattery composed of "three-dimensional bicontinuous interdigitated microelectrodes," and a University press release and a variety of media coverage has essentially decided the battery can save the world. While it is certainly impressive and may eventually fit a range of applications, there are still problems with the idea, and as of now it mainly exists in a paper in Nature Communications. It could take a while to go from the lab to your cell phone.
To the miracle claims: "The most powerful batteries on the planet are only a few millimeters in size, yet they pack such a punch that a driver could use a cellphone powered by these batteries to jump-start a dead car battery—and then recharge the phone in the blink of an eye." Whew!
Sounds great, right? I emailed Paul Braun, one of the researchers involved, and asked what the catch is. He said that though this battery can charge at speeds resembling capacitors, "a capacitor usually can be cycled millions of times. We have a long way to go in this regard. Almost all Li-ion batteries exhibit capacity fade with cycling, including our system." He added that this isn't a direct replacement for a capacitor, but "rather this is best for systems where the high energy density is particularly useful. Because of the 3-D structure, we can also provide capacitor-like power, but a million cycle life is quite unlikely."
The architecture of the batteries allows very short electron and ion transport distance; the entire fuel battery cell has a volume of 0.03 cubic millimeters. The design does yield impressive performance; as the press release says, "imagine juicing up a credit-card-thin phone in less than a second." The cycling question is definitely up in the air, though: in the paper, the authors write that the battery cell retained 64 percent of its initial energy after only 15 cycles, losing about 5 percent with each "low-rate" cycle. And the BBC reports (in one of the few appropriately skeptical pieces on the tech) that as the technology is scaled up for use in larger applications safety could become an issue thanks to the use of small amounts of a combustible liquid electrolyte.
I also asked Braun about manufacturing and if costs would be prohibitive, but he said the process would actually be relatively simple. "The key will be developing a manufacturing process which is compatible with both the battery and the device one wishes to power," he said.
Don't expect that all our devices will stay powered for a month after a one-second charge anytime soon, but there is clearly a lot of promise here. In the paper, the authors say the microbatteries could have a wide range of applications, "from medical implants to remote sensor networks."
Photo: Beckman Institute for Advanced Science and Technology