Scientists use graphene-based inks to 3D print ultralight supercapacitors

Researchers from the Lawrence Livermore National Laboratory and UC Santa Cruz have created the first ever 3D printed supercapacitors using an ultra-lightweight graphene aerogel. The technology could greatly improve energy storage in smartphones, electric cars, and wireless sensors.

Although supercapacitors were first built in the late 1950s, they remain a less common method of energy storage for portable electrical devices than batteries. Batteries provide power through chemical reactions, which take place between two electrodes and a chemical substance called an electrolyte. Capacitors (non-super ones) work in a completely different manner, using static electricity (electrostasis) to store energy. They also provide a few advantages over batteries, weighing less and containing no harmful chemicals or toxins.

Supercapacitors differ from capacitors, as they have much bigger conductive plates, both of which are soaked in an electrolyte, making supercapacitors a kind of capacitor-battery hybrid. These devices have capacitance values much higher than ordinary capacitors, and are used to supply rapid charges and discharges across a range of applications, such as within vehicles and elevators, where they are used for regenerative braking and short-term energy storage.

The LLNL team successfully 3D printed its supercapacitors in a graphene-oxide composite ink using a 3D printing process called direct-ink writing. The 3D printed supercapacitors are able to retain energy at a similar standard to those made with electrodes 10 to 100 times thinner. The complete findings of the study have been published in Nano Letters, January 20, under the title “Supercapacitors Based on Three-Dimensional Hierarchical Graphene Aerogels with Periodic Macropores.”

“This breaks through the limitations of what 2D manufacturing can do,” said engineer Cheng Zhu, the paper’s lead author. “We can fabricate a large range of 3D architectures. In a phone, for instance, you would only need to leave a small area for energy storage. The geometry can be very complex.”

Since supercapacitors can charge incredibly quickly compared to batteries, Zhu and co. believe their 3D printed supercapacitors could someday be used to create a whole new generation of electronic devices that could not be made using other synthetic methods. These devices could include fully customized smartphones and paper-based or foldable devices.

“We’re pioneering the marriage of 3D printing and porous materials,” said material and biomedical scientist Fang Qian, a co-author on the paper. “Think of a supercapacitor as a portable energy device, so anything that needs electricity would benefit from such a supercapacitor. If we can replace the standard (technology) with our lightweight, compact and high-performance supercapacitor, that would be a radical change.”

To 3D print the special supercapacitors, a regular 3D printer and filament would not have sufficed. Instead, the team used a graphene-based ink, which has an advantage over carbon-based alternatives because of its lightness, elasticity, and superior electrical conductivity. The graphene also contributes to the stability of the supercapacitors, which can retain their energy capacity even after 10,000 consecutive charging and discharging cycles.

“Additively manufactured 3D architectures for energy storage will improve energy and power characteristics for supercapacitors, enabling lightweight, miniaturized power sources,” said LLNL materials engineer Eric Duoss. “Graphene is a really incredible material because it is essentially a single atomic layer that can be created from graphite. Because of its structure and crystalline arrangement, it has really phenomenal capabilities.”

Over the next twelve months, the 3D printed supercapacitor team plans to develop new 3D designs which use different inks and which will improve the performance of existing materials.

“This is definitely a first step toward the future,” Zhu said. “There will be more to come.”