Scalable Holey Graphene Synthesis and Dense Electrode Fabrication toward High-Performance Ultracapacitors

Abstract

Graphene has attracted a lot of attention for ultracapacitor electrodes because of its high electrical conductivity, high surface area, and superb chemical stability. However, poor volumetric capacitive performance of typical graphene-based electrodes has hindered their practical applications because of the extremely low density. Herein we report a scalable synthesis method of holey graphene (h-Graphene) in a single step without using any catalysts or special chemicals. The film made of the as-synthesized h-Graphene exhibited relatively strong mechanical strength, 2D hole morphology, high density, and facile processability. This scalable one-step synthesis method for h-Graphene is time-efficient, cost-efficient, environmentally friendly, and generally applicable to other two-dimensional materials. The ultracapacitor electrodes based on the h-Graphene show a remarkably improved volumetric capacitance with about 700% increase compared to that of regular graphene electrodes. Modeling on individual h-Graphene was carried out to understand the excellent processability and improved ultracapacitor performance.

Densely packed graphene nanomesh-carbon nanotube hybrid film for ultra-high volumetric performance supercapacitors

“…However, the GNCN//GNCN symmetric supercapacitor in 6 M KOH electrolyte delivers a low energy density of 7.2 Wh kg À 1 due to its low voltage window (1 V). More interestingly, the GNCN//GNCN symmetric supercapacitor also exhibits a high volumetric energy density of 26 Wh L À 1 in 1 M Na 2 SO 4 aqueous electrolyte, higher than most previously reported carbon based supercapacitors in aqueous electrolyte (Figure 4b) [60,63,[67][68][69][70].…”

Holey Graphene as a Weed Barrier for Molecules

“…Our choice was also influenced by the number of techniques that enable the introduction of nanoscale pores of arbitrary size and location to graphene, including both electron-beam bombardment and chemical approaches. [30][31][32][33][34][35][36][37][38][39] These techniques will ultimately provide flexibility and precision in pattern shape and scale, including precise hole size and pitch.…”

Highly densified carbon electrode materials towards practical supercapacitor devices

“…Introducing pores in graphene platelets may facilitate ion/solvent diffusion across the graphene layers, enabling the assembly more ion-accessible even when the layers are densely stacked. The difference between the thermal stabilities of the crystalline and the non-crystalline regions in thermally exfoliated graphite oxide (TEGO) has been exploited to create holes by carefully controlling the temperature of the annealing atomosphere [61]. It was found that such a holey-graphene is easier to disperse in N-methyl-2-pyrrolidone (NMP) when compared to the original TEGO, since the mesopores created during the processing facilitated the penetration of NMP molecules.…”