Biomass-Derived Carbon Electrodes 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 CO 2 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 3D hierarchical micro-meso-macro porous biochar previously obtained, to synthesize high mass-loading freestanding electrode. Especially, the freestanding material (C 1000 G 0.2 ), owning 0.2 g SSP-900 and suffering carbonization at 1000 °C exhibits high specific surface area of 389.3 cm 2  g -1 , and self-doped N, O (2.75 %, 5.64 %). That awards C 1000 G 0.2 outstanding electrochemical properties, including high specific mass capacitance of 199.2 F g -1 , splendid specific area capacitance of 4.37 F cm -2 in 21.93 g cm -2 , 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 -1 , high energy density of 32.5 Wh kg -1 under the power density of 90.4 W kg -1 , 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.