Heterogeneous stacking carbon films for optimized supercapacitor performance

Abstract

Porous carbons are widely used as electrode materials for supercapacitors but the further increase in the performance is restricted by the challenge of tuning the porosity in the single type of carbons. The deteriorated ionic dynamics is a bottleneck for thick or high-mass-loading electrodes in the practical applications, requiring a rational design of electrodes. Herein, we demonstrate that, by simply stacking films made of carbons with differential pore features, the specific capacitance and ionic transport can be optimized based on the stacking order in the electrodes. Specifically, we find out that reduced graphene oxide (rGO) with large mesopores can efficiently improve the ionic transport when being placed in the middle, which is further supported by the finite element and molecular dynamics simulations. When an activated carbon YP50F, rGO and activated microwave exfoliated graphite oxide (aMEGO) are sequentially stacked with aMEGO nearby the separator, a high loading (∼210 μm, ∼10 mg, ∼12.7 mg cm–2) of active materials in the electrode delivers the higher capacitances (171.4 F g–1, 102.8 F cm–3, 2.2 F cm–2) compared to other stacking orders or single types of electrodes, in an electrolyte of ionic liquid in acetonitrile at a voltage of 2.7 V.