Graphene and carbon nanotube composite electrodes for supercapacitors with ultra-high energy density

TLDR

The study presents a graphene/SWCNT composite film fabricated by blending for high‑energy‑density supercapacitor electrodes. The composite is made by mixing graphene with SWCNTs, which act as conductive additive, spacer, and binder to enhance electrode performance. The graphene/SWCNT electrodes achieve specific capacitances of 290.6 F g⁻¹ (aqueous) and 201.0 F g⁻¹ (organic), delivering an energy density of 62.8 Wh kg⁻¹ and power density of 58.5 kW kg⁻¹ in organic electrolyte, and reaching 155.6 Wh kg⁻¹ in ionic liquid; SWCNT addition boosts energy by 23 % and power by 31 %, with a 29 % capacitance increase after 1000 cycles, making them comparable to NiMH batteries for hybrid and electric vehicles.

Abstract

We describe a graphene and single-walled carbon nanotube (SWCNT) composite film prepared by a blending process for use as electrodes in high energy density supercapacitors. Specific capacitances of 290.6 F g−1 and 201.0 F g−1 have been obtained for a single electrode in aqueous and organic electrolytes, respectively, using a more practical two-electrode testing system. In the organic electrolyte the energy density reached 62.8 Wh kg−1 and the power density reached 58.5 kW kg−1. The addition of single-walled carbon nanotubes raised the energy density by 23% and power density by 31% more than the graphene electrodes. The graphene/CNT electrodes exhibited an ultra-high energy density of 155.6 Wh kg−1 in ionic liquid at room temperature. In addition, the specific capacitance increased by 29% after 1000 cycles in ionic liquid, indicating their excellent cyclicity. The SWCNTs acted as a conductive additive, spacer, and binder in the graphene/CNT supercapacitors. This work suggests that our graphene/CNT supercapacitors can be comparable to NiMH batteries in performance and are promising for applications in hybrid vehicles and electric vehicles.