Cork-Derived Carbon Sheets for High-Performance Na-Ion Capacitors

S-doped carbon sheets have been easily prepared by deconstructingthe 3D cellular structure of a fully sustainable and renewable biomassmaterial such as cork through a mild ball-milling process. S-dopingof the material (>14 wt % S) has been achieved by using sulfurasan earth-abundant, cost-effective, and environmentally benign S-dopant.Such synthesized materials provide large Na storage capacities inthe range of 300-550 mAh g(-1) at 0.1 A g(-1) and can handle large current densities of 10 A g(-1), providing 55-140 mAh g(-1). Their increased packing density compared to the 3D pristine structureallows them to also provide good volumetric capacities in the rangeof 285-522 mAh cm(-3) at 0.1 A g(-1) and 53-133 mAh cm(-3) at 10 A g(-1). In addition, highly porous carbon sheets (S (BET) > 2700 m(2) g(-1)) have beenproducedfrom the same carbon precursor by rationally designing the chemicalactivation approach. These materials are able to provide good anionstorage capacities/capacitances of up to 100-114 mAh g(-1)/163-196 F g(-1). A sodium-ioncapacitor assembled with the optimized S-doped carbon sheets and thehighly porous carbon sheets with mass matching ratios provided thebest energy/power characteristics (90 Wh kg(-1) at29 kW kg(-1)) in combination with robust cycling stabilityover 10,000 cycles, with a capacity fade of only 0.0018% per cycle.