A novel approach to fabricate carbon sphere intercalated holey graphene electrode for high energy density electrochemical capacitors

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Vol. 317; pp. 461 - 470
• Main Authors: Wu, Shuxing, Hui, Kwan San, Hui, Kwun Nam, Yun, Je Moon, Kim, Kwang Ho
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-06-2017
• Subjects: Carbon sphere; Electrochemical capacitor; High energy density; Holey graphene; Holey graphene; Carbon sphere; High energy density; Electrochemical capacitor
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2017.02.040

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•Self-assembly of holey graphene sheets intercalates with carbon spheres.•The film electrode exhibits 207.1Fg−1 of specific capacitance.•Maximum specific energy and power of 29.5Whkg−1 and 22.6kWkg−1 are achieved.
Desirable porous structure and huge ion-accessible surface area are crucial for rapid electronic and ionic pathway electrodes in high-performance graphene-based electrochemical capacitors. However, graphene nanosheets tend to aggregate and restack because of van der Waals interaction among graphene sheets, resulting in the loss of ion-accessible surface area and unsatisfactory electrochemical performance. To resolve this daunting challenge, a novel approach is developed for the self-assembly of holey graphene sheets intercalated with carbon spheres (H-GCS) to obtain freestanding electrodes by using a simple vacuum filtration approach and a subsequent KOH activation process. Through the introduction of carbon spheres as spacers, the restacking of reduced graphene oxide (rGO) sheets during the filtration process is mitigated efficiently. Pores on rGO sheets produced by subsequent KOH activation also provide rapid ionic diffusion kinetics and high ion-accessible electrochemical surface area, both of which favor the formation of electric double-layer capacitance. Furthermore, a higher degree of graphitization of CSs in H-GCS thin film improves the electrical conductivity of the H-GCS electrode. The H-GCS electrode exhibits 207.1Fg−1 of specific capacitance at a current density of 1Ag−1 in 6MKOH aqueous electrolyte. Moreover, the symmetric electrochemical capacitor assembled with H-GCS electrodes and organic electrolyte is capable of delivering a maximum energy density of 29.5Whkg−1 and a power density of 22.6kWkg−1.