The Effect of CVD-Graphene at the Active-Layer/Current-Collector Interface for High-Performance Supercapacitor

Abstract

Supercapacitors, that is to say, electrochemical double-layer capacitors are considered very promising candidates for energy storage device due to their high specific energy and power densities, long cycle life, and fast charge and discharge rates. Typically, the specific capacitance of the ultra-capacitor with high rate capability is much less affected by the charge/discharge rates and thus is particularly attractive for high power applications such as heavy transport and electric vehicles. For such a high performance supercapacitor, it is important to consider the interface of active layer/electrolyte and the interface of the active layer/current collector. In the paper, we report that the presence of graphene layer between the active material and current collector has made it possible to improve the performance of supercapacitor. To demonstrate the advantages of Chemical vapor deposition (CVD) grown graphene, three types of working electrodes were fabricated for comparison by applying graphene films as the active materials in a symmetric two-electrode supercapacitor: 1) without CVD graphene, 2) with transferred CVD graphene on current collector, and 3) with direct-grown CVD graphene on current collector. The effect of graphene on current collector is analyzed by performing cyclic voltammetry (CV), galvanostatic charge/discharge measurement, and electrochemical impedance spectroscopy.