Freestanding biomass‐derived and self‐doped carbon electrodes with high loading for high‐performance supercapacitors

Supercapacitors with the performance advantages of high-power density are emerging materials for energy storage/conversion systems that can combat climate change caused by CO2 emissions and are of importance with the development of electronic products and artificial intelligence. But rationally preparing high-performance electrode with high mass-loading quantity remains challenge. Herein, we have opted for chitosan as well-structured binding agent to combine with active carbon (SSP-900), a 3-D hierarchical micro-meso-macro porous biochar we had previously obtained, to synthesize high mass-loading freestanding electrode. Especially, the freestanding material (C1000G0.2), owning 0.2 g SSP-900 and suffering carbonization at 1000 °C, exhibits high specific surface area of 389.3 cm2/g, and self-doped N, O (2.75%, 5.64%). That endows C1000G0.2 outstanding electrochemical properties, including high specific mass capacitance of 199.2 F/g, splendid specific area capacitance of 4.37 F/cm2 in 21.93 g/cm2, which is more competitive than conventional freestanding materials. Symmetrical supercapacitor with mass loading of 12 mg is assembled, and exhibits large specific capacitance of 65 F/g, high energy density of 32.5 Wh/kg under the power density of 90.4 W/kg, and capacitance stability of 98% after 10,000 cycles. The distinguished electrochemical performance of freestanding electrodes supplies prospective application for storing/converting electrical energy from intermittent solar and wind.