Universal self-assembly of graphene-based composites as free-standing hierarchical electrodes for high-performance aqueous hybrid capacitors

Abstract

For the development of aqueous hybrid capacitors, it is essential to fulfill the role of active materials and concentrate on the device's performance. However, these goals are challenging because the conventional electrodes meet a heterogeneous distribution of active materials and large-portion passive components. We develop a universal method to prepare free-standing hierarchical graphene-based composited electrodes here. Compared to conventional electrodes, this hierarchical electrode can distribute active materials effectively, improve ion diffusion, increase charge transfer, reduce parasitic reactions, decrease passive components, etc., which facilitates fulfilling the role of active materials and increases the device performance. Typically, the hierarchical electrodes show higher capacity for Fe3O4, NiCo-LDH, PANI, and active carbon. In addition, the hierarchical electrodes can generate a high energy density of 43.7 Wh kg−1 (based on the whole electrodes instead of active materials). Also, the preparation method of hierarchical electrodes is facile, energy-saving, eco-friendly, etc., facilitating the practical application. Such a universal preparation method and high electrochemical performance hold great potential for developing high-performance energy storage devices.