The ever-increasing demands for energy and environmental concerns due to burning fossil fuels are the key drivers of today's R&D of innovative energy storage systems. This paper provides an overview of recent research progress in graphene-based materials as electrodes for electrochemical energy storage. Beginning with a brief description of the important properties of single-layer graphene, methods for the preparation of graphene and its derivatives (graphene oxide and reduced graphene oxide) are summarized. Then, graphene-based electrode materials for electrochemical capacitors and lithium-ion batteries are reviewed. The use of graphene for improving the performance of lithium–sulfur and lithium–oxygen batteries is also presented. Future research trend in the development of high-power-density and high-energy-density electrochemical energy storage devices is analysed.

Novel hierarchical graphene/polypyrrole (GNS/PPy) nanosheet composites have been successfully fabricated for the first time based on an in situ chemical oxidation polymerization method. Sheet-like PPy with a thickness of 20–50 nm grown on the surface of the composites of the GNS/PPy polymerized at an early stage due to the dominated role of the sheet-like GNS and residue glucose in the synthesis process. Supercapacitors based on the hierarchical composite exhibit large electrochemical capacitance (318.6 F g⁻¹) at a scan rate of 2 mV s⁻¹ . They also show superior electrochemical rate capability and cyclic stability. The capacitance retained ∼95% (132.9 F g⁻¹) after 1000 cycles at a scan rate of 100 mV s⁻¹ . Accordingly, the hierarchical GNS/PPy nanosheet composites are potential electrode materials for electrochemical supercapacitors.