Tassel tree flowers-derived hierarchically porous carbons with high surface area for high-performance flexible all-solid-state symmetric supercapacitors

•Tassel tree flowers-derived carbon materials own a honeycomb-like porous structure.•Such carbon materials own high surface area, rich microporosity with a high N level.•Such carbon materials exhibit a superior capacitive behavior for all-state-solid capacitor. Waste biomass is a naturally abundant and sustainable resource, and however their unreasonable utilization could arouse some severe environmental issues and pollution. Thus, the efficient utilization and conversion of waste biomass are greatly essential in alleviating the burden on already-strained energy and environmental crisis. In this work, we reported a simple, one-step pyrolysis and activation strategy to prepare porous carbons for use as electrode materials of energy storage devices using waste biomass as carbon source. The obtained porous carbons not only exhibited a well-interconnected 3D honeycomb-like microstructure, but also owned a hierarchical porosity with abundant micropores and suitable proportion of mesopore, as well as nitrogen from the biomass being self-doped in the resultant carbon skeleton. The optimal material possessed a large accessible surface area of 3310 m2 g−1 and a high hierarchical porosity of 1.79 cm3 g−1. The obtained materials exhibited a remarkably electrochemical capacitive performance including a high rate capacity, and a high capacitance of 394 F g−1 at 0.5 A g−1 was delivered in 6 M KOH electrolyte. Importantly, the assembled symmetric flexible all-solid-state capacitor exhibited a high energy density of 18 Wh kg−1 and a power density of 246 W kg−1, as well as a good cycling stability of a 96 % capacitance retention after 5000 cycles in a PVA/KOH gel electrolyte. Our proposed strategy not only realized the large-scale utilization and conversion of waste biomass to ease environmental issues, but also achieved the possibility of the production of a high-performance supercapacitor electrode in industry, which was a sample to convert the waste biomass into a high-value-added product.