Over two-and-a-half years ago, researchers at Sandia National Laboratories developed what they claimed was the smallest battery yet produced. The lithium-based battery they produced was no bigger than a grain of sand, so small that one of its anodes consisted of nothing more than a single nanowire.
There didn’t seem to be any real-world applications for the battery, because it was created inside a transmission electron microscope (TEM). Instead it was intended to demonstrate a way forward in the miniaturization of batteries to satisfy a market in which gadgets are becoming smaller and smaller but the batteries used to run them remain rather large.
Now researchers at Harvard University are following up on Sandia's battery miniaturization by using a 3-D inkjet printing process enabled by nanoparticles made from lithium metal. This research brings 3-D printing to a new level, according to the researchers.
“Not only did we demonstrate for the first time that we can 3D-print a battery; we demonstrated it in the most rigorous way,” said Jennifer A. Lewis a professor at the Harvard School of Engineering and Applied Sciences (SEAS), in a press release.
The research, which was published in Advanced Materials (“3D Printing of Interdigitated Li-Ion Microbattery Architectures”), updates the traditional method of building electrodes that involves depositing thin films of solid materials. On it's own, this long-used technique results in solid-state micro-batteries that don’t store enough energy for today’s devices.
Instead the process Lewis and her colleagues employed used 3-D printing to build tightly interlaced, ultrathin electrodes. To do this, the team had to develop a special type of ink that would be electrochemically active and harden into layers as narrow as those produced by the thin-film manufacturing methods. The researchers developed ink for the anodes made from one compound of lithium metal oxide nanoparticles and from a different compound for the cathodes.
After depositing the inks onto two gold combs (a process you can watch on the video below), the stacks of interlaced anodes and cathodes were packaged into a container filled with electrolyte. The researchers were impressed with the performance measurements of the resulting battery.
“The electrochemical performance is comparable to commercial batteries in terms of charge and discharge rate, cycle life, and energy densities,” said Shen Dillon, an assistant professor of materials science and engineering at Harvard and one of Lewis' collaborators, in the press release. “We’re just able to achieve this on a much smaller scale.”
If the miniature batteries can be produce on a bulk scale, this could change the way in which small devices are powered and open up entirely new possibilities for electronic devices in both medial and non-medical applications.
Image: Jennifer A. Lewis, Harvard University