Supercapacitors based on graphenenanosheets using different non-aqueous electrolytes

Abstract

In this study, the electrochemical properties of graphene nanosheet (GNS) electrodes are evaluated in depth by cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) and electrochemical impedance spectroscopy (EIS) techniques in [Et₄N]BF₄/acetonitrile electrolyte, [BPy]BF₄/acetonitrile electrolyte, [BMIM]BF₄/acetonitrile electrolyte and [P_4,4,4,4]BF₄/acetonitrile electrolyte, respectively. The electrochemical results exhibit that GNSs show good supercapacitive properties in these aforementioned four non-aqueous electrolytes, especially in [Et₄N]BF₄/acetonitrile electrolyte. It is also observed that the rate performance and the specific capacitance of GNS electrode increase in the order of [P_4,4,4,4]BF₄/acetonitrile < [BMIM]BF₄/acetonitrile ≈ [BPy]BF₄/acetonitrile < [Et₄N]BF₄/acetonitrile in these four non-aqueous electrolytes. The reasons are attributed to the difference of the relative ionic size and the discrepancy in the functional group among these four non-aqueous electrolytes, which result in the differences of equivalent series resistance, charge transfer resistance, and rate performance. In addition, the GNS electrode shows excellent stability in these four non-aqueous electrolytes after 1500 repeating charge–discharge cycles. These results may provide valuable information to explore new electrolytes and illustrate the exciting potential for high performance supercapacitors based on GNSs.