Robust Production of Ultrahigh Surface Area Carbon Sheets for Energy Storage

Nanostructured carbon materials play essential roles in electrochemical energy storage devices. However, scalable production of high surface area carbon with a cost-effective process while controlling the morphology is challenging. Herein, a one-step procedure to produce carbon sheets with very high specific surface area up to 3411 m² g^-1 by direct pyrolysis of dipotassium ethylene diamine tetraacetate is reported. Unlike that of biomass-pyrolyzed carbons, the surface area of prepared carbon sheets is not sensitive to pyrolysis conditions (e.g., heating temperature and time), which makes the production robust and scalable. Moreover, the pore structure is stable against posttreatments, including solvent washing, which are detrimental to that of graphene-based soft sheet assemblies. When used as supercapacitor electrodes, the ultrahigh surface area carbon sheets (HSACS) show a high specific capacitance of 268 F g^-1 at 5 mV s^-1 , and retain 70% of the capacitance at 100 times higher scan rate in 6 m KOH aqueous electrolyte. Furthermore, the HSACS also exhibit a high specific capacitance of 266 F g^-1 within a 1.6 V symmetric supercapacitor potential window in 2 m Li₂ SO₄ aqueous electrolyte. The symmetric supercapacitor delivers a maximum specific energy of 23.6 W h kg^-1 and high power density of 6.4 kW kg^-1 .