N-doped hollow carbon spheres intercalated graphene film induced macroporous frameworks for ultrahigh volumetric energy density supercapacitor

Ideal electrodes should hold well-defined pore size distribution, high electrical conductivity and superior compatibility. Herein, we present a scalable strategy for the design and generation of macroporous frameworks based on N-doped hollow carbon spheres intercalated graphene film (GNC). In the unique structure, hollow carbon spheres separate the graphene nanosheets and provide convenience for ion entering the film and maximize the ion-accessible surface area. In situ deposition high performance MnO2 on the surface of GNC film can help to enhance the specific capacity of the compounds. The obtained GNC/MnO2 binder-free supercapacitor electrode exhibits ultrahigh volumetric capacitance 532.7 F cm(-3) at 2 mV s(-1). An asymmetric supercapacitor based on GNC/MnO2//GNC shows an ultrahigh volumetric energy density of 45.9 Wh L-1 at 1024 W L-1, which is much higher than the reported carbon based materials in aqueous electrolytes. The device also shows an excellent cycling stability with 93.1% initial capacitance after 5000 charge/discharge cycles. The device can light two LEDs, which indicates the potential of the composite for practical application. (C) 2019 Published by Elsevier B.V.