Nanocellular graphene (NCG) is a specialized form of graphene that achieves a large specific surface area by stacking multiple layers of graphene and controlling its internal structure with a nanoscale cellular morphology. Although the material has the potential to improve the performance of electronic devices, energy devices and sensors, its development has been stymied by defects that occur during the manufacturing process. Cracks often appear when forming NCG, and scientists are looking for new processing technologies that can fabricate homogeneous, crack-free and seamless NCGs at appropriate scales.
A promising new method that produced crack-free NCG has been reported by researchers at the Institute of Materials Research, Tohoku University (Japan; www.nem2.imr.tohoku.ac.jp) in a recent issue of Advanced Materials. The method uses a process known as dealloying, which exploits the varying miscibility of alloy components in a molten-metal bath. This process selectively corrodes certain components of the alloy while preserving others.
“We discovered that carbon atoms rapidly self-assemble into crack-free NCG during liquid metal dealloying of an amorphous manganese-carbon precursor in molten bismuth [diagram],” says Won-Young Park, a graduate student at Tohoku University.
Park and his colleagues demonstrated that NCGs developed by this method exhibited high tensile strength (34.8 MPa) and high electrical conductivity (1.6 × 104 S/m) after graphitization. Moreover, they put the material to the test in a sodium-ion battery (SIB). “We used the developed NCG as an active material and current collector in a SIB, where it demonstrated a high rate, long life and excellent deformation resistance,” says Park. “Ultimately, our method of making crack-free NCG will make it possible to raise the performance and flexibility of SIBs — an alternative technology to lithium-ion batteries for certain applications, particularly in large-scale energy storage and stationary power systems where cost, safety and sustainability considerations are paramount.”