Morphology Effect of Vertical Graphene on the High Performance of Supercapacitor Electrode

Abstract

Graphene and its composites are widely investigated as supercapacitor electrodes due to their large specific surface area. However, the severe aggregation and disordered alignment of graphene sheets hamper the maximum utilization of its surface area. Here we report an optimized structure for supercapacitor electrode, i.e., the vertical graphene sheets, which have a vertical structure and open architecture for ion transport pathway. The effect of morphology and orientation of vertical graphene on the performance of supercapacitor is examined using a combination of model calculation and experimental study. Both results consistently demonstrate that the vertical graphene electrode has a much superior performance than that of lateral graphene electrode. Typically, the areal capacitances of a vertical graphene electrode reach 8.4 mF/cm(2) at scan rate of 100 mV/s; this is about 38% higher than that of a lateral graphene electrode and about 6 times higher than that of graphite paper. To further improve its performance, a MnO2 nanoflake layer is coated on the surface of graphene to provide a high pseudocapacitive contribution to the overall areal capacitance which increases to 500 mF/cm(2) at scan rate of 5 mV/s. The reasons for these significant improvements are studied in detail and are attributed to the fast ion diffusion and enhanced charge storage capacity. The microscopic manipulation of graphene electrode configuration could greatly improve its specific capacitance, and furthermore, boost the energy density of supercapacitor. Our results demonstrate that the vertical graphene electrode is more efficient and practical for the high performance energy storage device with high power and energy densities.

Vertically Aligned Graphene Nanosheet Arrays: Synthesis, Properties and Applications in Electrochemical Energy Conversion and Storage

“…Reproduced with permission. [26] Copyright 2016, American Chemical Society. grow directly on conductive substrates, and thus the non-conductive polymeric binders that inevitably leads to the increase of electrical resistance for charge transport and the reduction of power and energy densities can be avoided.…”

“…The effects of graphene orientation and shape on the electrochemical properties of graphene-based electrodes have been investigated. [26] Figure 5d-i present the morphologies of graphene sheets with different orientations and their impact on the ion transport capability and the charge storage capacity. As compared with the horizontally packed graphene layers, VAGNA electrodes provide rich open channels for the access of electrolyte, enable the shortest straight path for ion exchange, and maximize the utilization of surface area.…”

“…[27] With a thickness of several to tens of graphite carbon layers, VAGNAs are also named as carbon nanoflake arrays or carbon nanowall arrays elsewhere. [26,28] VAGNAs are generally synthesized by PECVD with gaseous carbon sources, in which 2D graphene nanosheets are grown perpendicularly to the substrates to construct a 3D ordered and interconnected array structure with enriched edges of graphene sheets exposed (Figure 1g,h). Compared with the graphene prepared in conventional CVD systems, reactive species in the non-equilibrium plasma conditions enable the growth of graphene on various substrates without using metal catalysts and at relatively low temperature.…”

Recent progress in carbon-based nanoarchitectures for advanced supercapacitors

“…As-fabricated VArGO electrodes showed excellent volumetric (171 F cm −3 ) and areal (1.83 F cm −2 ) capacitances in 6 M KOH due to its appropriate interlayer distances and pores. Deng et al [115] adopted model calculation and experimental test to investigate the relation of electrode structure and capacitive performance with respect to the different orientation of graphene sheets. Simulation results indicated that the oriented structure and morphology of graphene sheets have strong influence on the ion transfer ability and the charge accumulation capability.…”

Sonochemical Preparation and Subsequent Fixation of Oxygen‐Free Graphene Sheets at N,N‐Dimethyloctylamine‐Aqua Boundary

“…In the same time, obtaining 3D graphene particles as versatile building blocks for bottom-up assembly of advanced functional materials is a very difficult problem, according to many researchers [50][51][52]. e development of cost-effective method for producing 2D and 3D graphene stacks with specified dimensions is promising for obtaining van der Waals heterostructures containing different semiconductors in the interlayer space [53,54].…”