New 3-D Battery Is a Wait-Reduction Device

Now there’s a battery that will literally charge phones in seconds and charge laptops in minutes. The implications for electric vehicle infrastructure, as well as medical devices and military applications are sure to be considered next.

The Paul Braun Research Group at the University of Illinois at Urbana-Champaign has developed a “three-dimensional nanostructure” for batteries that facilitates dramatically faster charging and discharging, without sacrificing energy storage capacity.

“This system that we have gives you capacitor-like power with battery-like energy,” said Braun, a professor of Materials Science and Engineering. “Most capacitors… can release energy very fast, but they can’t [store] much. Most batteries store a reasonably large amount of energy, but they can’t provide or receive energy rapidly. This does both.”

The researchers set out to improve the performance of lithium-ion (Li-ion) or nickel metal hydride (NiMH) rechargeable batteries, which typically degrades significantly when they are rapidly charged or discharged. However, they said, the structure they have developed “is general, so any battery material that can be deposited on the metal frame could be used.”

“We like that it’s very universal, so if someone comes up with better battery chemistry, this concept applies,” commented Braun, who is also affiliated with the Materials Research Laboratory and the Beckman Institute for Advanced Science and Technology at Illinois. “This is not linked to one very specific kind of battery, but rather it’s a new paradigm in thinking about a battery in three dimensions, for enhancing properties.”

Making the active material in the battery a thin film allows for very fast charging and discharging, but reduces the capacity to nearly zero because the active material lacks volume to store energy.Braun’s group wraps a thin film into a three-dimensional structure, achieving both high capacity and large current. They have demonstrated battery electrodes that can charge or discharge in a few seconds—10 to 100 times faster than equivalent bulk electrodes—yet can perform normally in existing devices

Braun is particularly optimistic for the batteries’ potential in electric vehicles. Battery life and recharging time are major limitations of EVs—engendering “range anxiety” in drivers and potential buyers. Long-distance road trips can require patience and planning, if the battery only lasts for 100 miles and then requires an hour to recharge.

Using the new type of battery that Braun’s group has developed, it could potentially take as long to recharge an EV as it would to refill a gas guzzler at a conventional station. According to Braun, “If you had five-minute charge capability, you would think of this the same way you do an internal combustion engine. You would just pull up to a charging station and fill up.”

The key to the group’s novel 3-D structure is self-assembly. They begin by coating a surface with tiny spheres, packing them tightly together to form a lattice. Trying to create such a uniform lattice by other means is time-consuming and impractical, but the inexpensive spheres settle into place automatically.

Then the researchers fill the space between and around the spheres with metal. The spheres are melted or dissolved, leaving porous 3-D metal scaffolding, like a sponge. Then a process called electropolishing uniformly etches away the surface of the scaffold to enlarge the pores and make an open framework. Finally, the researchers coat the frame with a thin film of the active material.

The result is a bicontinuous electrode structure with small interconnects, so the lithium ions can move rapidly; a thin-film active material, so the diffusion kinetics are rapid; and a metal framework with good electrical conductivity.

All of the processes the group used are also used at large scales in industry so the technique could be scaled up for manufacturing.

The U.S. Army Research Laboratory and the Department of Energy supported this work. Visiting scholar Huigang Zhang and former graduate student Xindi Yu were co-authors of the paper. The researchers’ findings have been published in the online edition of Nature Nanotechnology.