Freestanding flexible graphene foams@polypyrrole@MnO2 electrodes for high-performance supercapacitors

A new composite electrode design was successfully fabricated based on 3D flexible graphene foams (GF) with interconnected macropores as the freestanding substrate and a composite of MnO2 nanoparticles and polypyrrole (PPy) as an integrated electrode. Under assistance of PPy, the microscopic morphology of MnO2 changed from flower-like to nanoparticles, and correspondingly, a high specific capacity of 600 F g(-1) at a current density of 1 A g(-1) was obtained from the GF@PPy@MnO2 nanoparticles composite electrode. Moreover, over 92% of the initial capacity was retained after 5000 cycles at 30 A g(-1). Also, the role of PPy in improving the electrochemical performance of the composite electrode was investigated. We also tested a full symmetric supercapacitor of GF@PPy@MnO2//GF@PPy@MnO2 obtaining the maximum energy density of 28 W h kg(-1) at 508 W kg(-1) and the maximum power density of 13 kW kg(-1) at 14 W h kg(-1). This well-designed nanostructured composite electrode could be a promising electrode material for high-performance supercapacitors.