Heteroatom-doped hierarchically porous thick bulk carbon derived from a Pleurotus eryngii/lignin composite: a free-standing and high mass loading electrode for high-energy-density storage

It is critical to prepare self-supported carbonaceous electrode materials that enable high-mass loading and efficient ion/electron transport through a simple and sustainable method. Herein, for the first time, heteroatom-doped (O, N, and S) hierarchically porous thick bulk carbon is synthesized by carbonizing Pleurotus eryngii (PE) and lignosulfonate (LS) mixed precursors. After carbonization, the generated thick bulk carbon consists of interconnected macropores at the micrometer scale, with micropores and mesopores densely covering the pore walls. The carbon material displays a large specific surface area ranging from 315.5 to 960.2 m(2) g(-1) and is uniformly doped with O (14.8-19.1%), N (1.73-2.97%) and S (1.20-1.94%), endowing it with excellent ion transport and charge storage properties. As a result, the obtained thick bulk carbon electrode with a mass loading of 58.0 mg cm(-2) achieves an outstanding capacitance of 25.0 F cm(-2) (112.0 F cm(-3)) at 10 mA cm(-3) and a superior rate capability of 14.3 F cm(-2) (66.9 F cm(-3)) at 200 mA cm(-3). The assembled symmetric supercapacitor device delivers a high areal energy density of 2.56 mWh cm(-2) at a power density of 0.64 mW cm(-2) with an excellent stability of 91.1% after 15 000 cycles at 50 mA cm(-2). This facile and green synthesis strategy provides new carbonaceous electrode design concepts for high-energy-density storage.