Self-assembling 3D Batteries Take a Step Forward

17 May 2018
An artist rendering of the 3D battery architecture with interpenetrating anode, separator and cathode about 20 nanometers in size. Source: Cornell University

More consumers are adopting electric devices and along the way these consumers are demanding a reduction in the time it takes to recharge these devices. The more devices we acquire, the more time is spent charging them with a battery.

Now, a group of researchers from Cornell University has developed a new energy storage device architecture that has the potential to accelerate the time it takes to recharge electronic devices.

The idea is that instead of having batteries’ anodes and cathodes on either side of a non-conducting separator, intertwine the components in a self-assembling, 3D gyroidal structure with thousands of nanoscale pores filled with the components needed for energy storage and delivery.

“This three-dimensional architecture basically eliminates all losses from dead volume in your device,” said Ulrich Wiesner, professor of engineering at Cornell University. “More importantly, shrinking the dimensions of these interpenetrated domains down to the nanoscale, as we did, gives you orders of magnitude higher power density. In other words, you can access the energy in much shorter times than what’s usually done with conventional battery architectures.”

How fast could this new architecture charge devices? Because the battery’s elements are being shrunk down to the nanoscale level, it could take as little as seconds to charge a device.

How They Did It

The battery architecture is based on block copolymer self-assembly. The gyroidal thin films of carbon — the battery’s anode generated by block copolymer self-assembly — feature thousands of periodic pores about 40 nanometers wide. These pores are coated with a 10 nanometer thick, electronically insulating but ion-conducting separator through electropolymerization.

Sulfur is used as the cathode material in an amount that doesn’t quite fill the remainder of the pores. Sulfur accepts electronics but doesn’t conduct electricity. The final step is to backfill with an electronically conducting polymer known as PEDOT, or polyethylenedioxythiophene.

That’s vital, since defects like holes in the separator are what can lead to catastrophic failure giving rise to fires in mobile devices such as cellphones and laptops.

Wiesner said the battery is just a proof of concept at this point and multiple recharging and discharging of the battery gradually degrades the PEDOT charge collector, which doesn’t experience the volume expansion that sulfur does.

“When the sulfur expands you have these little bits of polymer that get ripped apart, and then it doesn’t reconnect when it shrinks again,” Wiesner said. “This means there are pieces of the 3D battery that you then cannot access.”

The full research can be found in the journal Energy & Environmental Science.

To contact the author of this article, email peter.brown@ieeeglobalspec.com

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