High-performance discarded separator-based activated carbon for the application of supercapacitors

• Discarded separator from end-of-life supercapacitors is used as carbon source. • Separator-based activated carbon with good electrochemical properties is prepared. • ACS-3 organic supercapacitor exhibits an energy density of 41.82 Wh/kg. The high-performance activated carbon prepared from low-cost precursors is urgently needed for supercapacitors. In this paper, a novel activated carbon that has excellent electrochemical performance and uses the discarded separators of end-of-life supercapacitors as precursors is proposed. Through high-temperature carbonization and subsequent activation treatments, the obtained separator-based activated carbon had a high specific surface area of 2187.36 m 2 /g. In addition, it had a thin carbon sheet structure and a small amount of microcrystalline structures, which shorten ion transport distance and improve electrical conductivity. These characteristics endowed a high specific capacitance of 208 F/g at 1 A/g in an aqueous electrolyte, which remained at 82.2% even at a high current density of 10 A/g. In addition, after 10,000 cycles, the capacitance still remained at 93.42%, indicating great cycle stability. Furthermore, when a high-voltage organic electrolyte was used, the supercapacitor assembled by the separator-based activated carbon delivered a high energy density of 41.82 Wh/kg at a power density of 1349.2 W/kg, suggesting great application potential. Overall, this work provides an alternative method for recycling discarded cellulose separators from end-of-life commercial supercapacitors, which would be feasible for waste secondary battery recycling.