Binder Free Graphene- Based Electrodes with Excellent Pseudocapacitive Performance

Owing to the high impact of the electrode’s architecture on the energy storage and power performance, it is very important to create optimum structures that provide efficient short paths for ion and charge transportation. Given excellent advantages of graphene, e.g. very high surface area, and excellent mechanical properties, this material is an ideal candidate to serve as an electrode matrix to stabilise electroactive materials for the charge-discharge process [1].  

In this study, three dimensional (3D) binder free graphene composites have been synthesised by a two-step process, a chemical vapour deposition of the graphene followed by a chemical or electrochemical deposition of the redox counterpart. Pure graphene (GN), Polyaniline-graphene (PANI-GN), Polypyrrole-graphene (PPY-GN) and some other electrodes will be described in this work, and their electrochemical performance  will be studied by using  combined cyclic voltammetry, impedance spectroscopy and galvanostatic charge discharge techniques. Effects of the electrode dimensionality (3D vs 2D) and the binder on the performance will be investigated and explained.

Figure 1 (a) is a SEM image of 3D graphene foam. The open porosity feature of the foam facilitates effectively the ion intercalation and extraction. Figures 1 (b) and 1 (c) are the cyclic voltammetry and Nyquist curve of the 3D PANI-GN. In contrast to the pure graphene and PANI, the composite electrode showed a much better electron conductivity and higher performance.

The performance data have also revealed that using the porous 3D graphene foam as the electrode matrix and eliminating the insulating binder from the electrode structures result in an improved conductivity of the electrode, with excellent cycle life. The improved electrochemical performance efficiency is due to the dual energy storage mechanism and the synergetic effect of the graphene foam and redox counterpart.

Reference:

1.            Chabi, S., et al., Ideal Three‐Dimensional Electrode Structures for Electrochemical Energy Storage. Advanced Materials, 2014. 26(15): p. 2440-2445.

Figure caption

Figure 1: SEM image of graphene foam (a) cyclic voltammetry of 3D PANI-GN (b) and Nyquist curve of 3D PANI-GN in 0.5 M H2SO4.