Compressed and Crumpled Porous Carbon Electrode for High Volumetric Performance Electrical Double-Layer Capacitors

The 2D carbon sheets have great potential for the construction of compact electrodes with high volumetric performance for electrical double-layer capacitors (EDLCs), by virtue of their excellent electrical conductivity, high exposed surface area, free of interpores, and unimpeded ion-diffusion channels. However, 2D nanosheets restack and aggregate during the preparation processes of electrodes, reducing available surface area, and limiting transport of ions. Herein, a facile and scalable method is presented to prepare highly porous crumple carbon balls (PCCBs) assembled by 2D carbon nanosheets. Such a unique nanostructure endows the PCCB electrode with large electrolyte-accessible surface area and short ion-diffusion pathways even when compressed at 40 MPa. Electrochemical evaluations in 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4) electrolyte indicate that the compressed PCCB electrodes still show superior gravimetric (103 F g(-1)) and volumetric capacitances (127 F cm(-3)) at 1 A g(-1). The highest volumetric energy density of symmetrical EDLC based on compressed PCCB-based electrode is 53.9 Wh L-1. This work provides a new direction for the development of high volumetric energy density carbon-based EDLCs.