Micro-corrugated graphene sheet enabled high-performance all-solid-state film supercapacitor

Abstract

All-solid-state flexible graphene-based film supercapacitors have been widely studied thanks to the extraordinary features of graphene and ever-growing interest in wearable electronics. However, strong π-π interactions between graphene sheets decrease the accessible surface area for electrolyte ions, which impairs the electrochemical performance. To address this issue, a graphene oxide (GO)-based gel film precursor was directly reduced in a liquid, and the water molecules between the GO sheets behave as interlayer spacers, which significantly lowers the interlayer attractive force and the frictional force. The graphene sheets shrink as the result of the in-plane contraction forces because of the removal of functional groups on the GO sheets during reduction, leading to a freestanding and corrugated graphene-based film. This corrugated morphology effectively mitigates the compact stacking of the sheets, causing more surface area be exposed to the electrolyte ions. Electrochemical measurements show that a flexible film supercapacitor using such corrugated graphene-based films as the active electrodes shows large specific capacitances (127 mF cm−2, 107 F cm−3), ultrahigh volumetric energy density (14.8 Wh L−1 at 53.6 W L−1, 10.4 Wh L−1 at 1.134 kW L−1), and excellent capacitance retention, far exceeding that of many previously reported freestanding graphene-based film supercapacitors.