24 September 2018
3D films for better supercapacitors
Published online 15 June 2016
Three-dimensional graphene films can store charge and even hydrogen.
Materials scientists have created a new brand of three-dimensional, porous graphene film that is potentially useful for making high-performance supercapacitors1.
This film can also be used in gas absorption, batteries and hydrogen storage.
Current techniques produce graphene films that have lost much of their original surface area and lack ion-transporting pores.
But Maher El-Kady and his colleagues from Cairo University, Egypt, and University of California, USA, have overcome this by dispersing and freezing aqueous graphene in liquid nitrogen. The ice crystals formed in liquid nitrogen prevent the graphene films from sticking together.
Evaporating the ice crystals leaves behind porous, three-dimensional honeycomb-like graphene films.
Unlike graphene paper, both sides of each graphene film are accessible to electrolytes and can thus store a huge amount of charge. The films are low resistance to charge transport — reducing charge losses during long-term use.
All-solid-state supercapacitors made of the graphene films retain their ability to store energy even after 500 cycles of repeated bending and unbending, the researchers say.
“Besides supercapacitors, the graphene films could potentially be used as catalysts and electrode materials for batteries,” says Yuanlong Shao, the lead author of the study.
Shao, Y. et al. 3D freeze-casting of cellular graphene films for ultrahigh-power-density supercapacitors. Adv. Mater. http://dx.doi.org/10.1002/adma.201506157 (2016).