A microsupercapacitor designed by scientists at Rice University that may find its way into personal and even wearable electronics is getting an upgrade. The laser-induced graphene device benefits greatly when boron becomes part of the mix.
The Rice lab of chemist James Tour uses commercial lasers to create thin, flexible supercapacitors by burning patterns into common polymers. The laser burns away everything but the carbon to a depth of 20 microns on the top layer, which becomes a foam-like matrix of interconnected graphene flakes.
By first infusing the polymer with boric acid, the researchers quadrupled the supercapacitor’s ability to store an electrical charge while greatly boosting its energy density.
Rice scientists made this supercapacitor with interlocked “fingers” using a laser and writing the pattern into a boron-infused sheet of polyimide. Courtesy of the Tour Group
Heteroatom-doped graphene materials have been intensely studied as active electrodes in energy storage devices. Here, we demonstrate that boron-doped porous graphene can be prepared in ambient air using a facile laser induction process from boric acid containing polyimide sheets. At the same time, active electrodes can be patterned for flexible microsupercapacitors. As a result of boron doping, the highest areal capacitance of as-prepared devices reaches 16.5 mF/cm2, 3 times higher than nondoped devices, with concomitant energy density increases of 5–10 times at various power densities. The superb cyclability and mechanical flexibility of the device are well-maintained, showing great potential for future microelectronics made from this boron-doped laser-induced graphene material.
The simple manufacturing process may also be suitable for making catalysts, field emission transistors and components for solar cells and lithium-ion batteries, they said.
The two-step process produces microsupercapacitors with four times the ability to store an electrical charge and five to 10 times the energy density of the earlier, boron-free version. The new devices proved highly stable over 12,000 charge-discharge cycles, retaining 90 percent of their capacitance. In stress tests, they handled 8,000 bending cycles with no loss of performance, the researchers reported.
Tour said the technique lends itself to industrial-scale, roll-to-roll production of microsupercapacitors. “What we’ve done shows that huge modulations and enhancements can be made by adding other elements and performing other chemistries within the polymer film prior to exposure to the laser,” he said.
“Once the laser exposes it, those other elements perform new chemistries that really increase the supercapacitor’s performance. This is a step in making these even more amenable for industrial applications.
SOURCES – Rice University, ACS Nano