CVD-graphene for low equivalent series resistance in rGO/CVD-graphene/Ni-based supercapacitors.

Reduced equivalent series resistance (ESR) is necessary, particularly at a high current density, for high performance supercapacitors, and the interface resistance between the current collector and electrode material is one of the main components of ESR. In this report, we have optimized chemical vapor deposition-grown graphene (CVD-G) on a current collector (Ni-foil) using reduced graphene oxide as an active electrode material to fabricate an electric double layer capacitor with reduced ESR. The CVD-G was grown at different cooling rates-20 °C min-1, 40 °C min-1 and 100 °C min-1-to determine the optimum conditions. The lowest ESR, 0.38 Ω, was obtained for a cell with a 100 °C min-1 cooling rate, while the sample without a CVD-G interlayer exhibited 0.80 Ω. The CVD-G interlayer-based supercapacitors exhibited fast CD characteristics with high scan rates up to 10 Vs-1 due to low ESR. The specific capacitances deposited with CVD-G were in the range of 145.6 F g-1-213.8 F g-1 at a voltage scan rate of 0.05 V s-1. A quasi-rectangular behavior was observed in the cyclic voltammetry curves, even at very high scan rates of 50 and 100 V s-1, for the cell with optimized CVD-G at higher cooling rates, i.e. 100 °C min-1.