Self-assembling 3D battery would charge in
May 18, 2018
The world is a big place, but it's gotten
smaller with the advent of technologies that put people from across the
globe in the palm of one's hand. And as the world has shrunk, it has
also demanded that things happen ever faster - including the time it
takes to charge an electronic device.
A cross-campus collaboration led by Ulrich Wiesner, professor of
engineering in the at Cornell University, addresses this demand with a
novel energy storage device architecture that has the potential for
The group's idea: Instead of having the batteries' anode and cathode on
either side of a nonconducting separator, intertwine the components in a
self-assembling, 3D gyroidal structure, with thousands of nanoscale
pores filled with the elements necessary for energy storage and
"This is truly a revolutionary battery architecture," said Wiesner,
whose group's paper, "Block Copolymer Derived 3-D Interpenetrating
Multifunctional Gyroidal Nanohybrid for Electrical Energy Storage," was
published May 16 in Energy and Environmental Science, a publication of
the Royal Society of Chemistry.
"This three-dimensional architecture basically eliminates all losses
from dead volume in your device," Wiesner said. "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 is that? Wiesner said that, due to the dimensions of the battery's
elements being shrunk down to the nanoscale, "by the time you put your
cable into the socket, in seconds, perhaps even faster, the battery
would be charged."
The architecture for this concept is based on block copolymer
self-assembly, which the Wiesner group has employed for years in other
devices, including a gyroidal solar cell and a gyroidal superconductor.
Joerg Werner, Ph.D. '15, lead author on this work, had experimented with
self-assembling photonic devices, and wondered if the same principles
could be applied to carbon materials for energy storage.
The gyroidal thin films of carbon - the battery's anode, generated by
block copolymer self-assembly - featured thousands of periodic pores on
the order of 40 nanometers wide. These pores were then coated with a 10
nm-thick, electronically insulating but ion-conducting separator through
electropolymerization, which by the very nature of the process produced
a pinhole-free separation layer.
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.
next step is the addition of the cathode material - in this case, sulfur
- in an amount that doesn't quite fill the remainder of the pores. Since
sulfur can accept electrons but doesn't conduct electricity, the final
step is backfilling with an electronically conducting polymer - known as
While this architecture offers proof of concept, Wiesner said, it's not
without challenges. Volume changes during discharging and charging the
battery gradually degrade the PEDOT charge collector, which doesn't
experience the volume expansion that sulfur does.
"When the sulfur expands," Wiesner said, "you have these little bits of
polymer that get ripped apart, and then it doesn't reconnect when it
shrinks again. This means there are pieces of the 3D battery that you
then cannot access."
The group is still perfecting the technique, but applied for patent
protection on the proof-of-concept work.