Layer-Stacking Activated Carbon Derived from Sunflower Stalk as Electrode Materials for High-Performance Supercapacitors

Recently, interest in the use of carbonaceous materials derived from sustainable biomass wastes for supercapacitors (SCs) has grown. The sustainable sunflower stalk is selected as the raw material for preparing activated carbon (AC), using a simple hydrothermal carbonization (HTC) combining an effective activation method. The as-prepared AC sample possesses a unique mesoporous layer-stacking structure which has an unexpected surface area up to 1505 m2 g–1 as well as a pore size of 3.6 nm on average. As an electrode material for SCs, the AC demonstrates high electrochemical storage capacity, with the excellent capacitances of 365 and 263 F g–1 measured by three-electrode and symmetrical SCs systems, respectively. An outstanding capacitance retention rate and a good stability value maintained after 15 000 cycles are close to 81 and 95%, respectively, which are obtained at a current density of 20 A g–1. Further, the symmetrical SCs exhibits an energy density as high as 35.7 Wh kg–1 under the condition of a p...