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With the intensifying energy crisis, it is urgent to develop green and sustainable energy storage devices. Supercapacitors have attracted great attention for their extremely high power, ultra-long lifetime, low-cost maintenance, and absence of heavy metal elements. Electrode materials are the kernel of such devices, and graphenes are of great interest for use as electrodes for their tremendous potential. The three-dimensional (3D) network structure of graphenes have been recently highlighted as potential electrode materials of supercapacitors. In this review, supercapacitors based on the 3D graphene networks are surveyed in terms of aqueous and non-aqueous systems. The powdery and bulky 3D graphene materials are discussed for fabricating the electrodes. Lastly, challenges and perspectives of the graphene-based supercapacitors are presented. [ABSTRACT FROM AUTHOR]

Potassium ion batteries are promisingly proposed for the large cale energy storage. However, potassium with large ion radius causes severe volumetric expansion of anodes during charging, which deteriorates the rate and the cycling performances of batteries. Herein, a honeycomb-like graphene monolith with rich micropores is prepared. The monolith is further applied as the binder-free anode for potassium ion batteries. It shows the remarkable rate performance with a capacity of 180 mAh g−1 at a current density of 10 A g−1, and it can stably run for 4000 cycles at 1 A g−1. Kinetic studies and theoretical analyses reveal that the large graphitic interlayer spacing, the nitrogen doping, and the 3D network structure can significantly promote the diffusion rate, the absorption of potassium ions, as well as the transports of electrons and ions. The graphene-based potassium ion batteries can thus boost the development of renewable energies. [Display omitted] • Defect-rich monolithic graphene with high specific surface area was prepared. • Zinc-guided graphene monolith was used as a binder-free potassium-storage anode. • Large interlayer spacing, nitrogen doping and 3D network improved performances. [ABSTRACT FROM AUTHOR]