Biomass-derived multi-heteroatom-doped carbon materials for high-performance solid-state symmetric supercapacitors with superior long-term cycling stability

In order to fabricate high-performance supercapacitors with desirable energy density and excellent cycling stability, this work aimed to synthesize biomass-derived carbon materials with great electrochemical performance, especially with superior long-term cycling stability, via a facile and simple process. Herein, we have fabricated three kinds of biomass-derived multi-heteroatom-doped carbon materials, using laver, soybean milk and soybean milk (Ag⁺) as the precursors, labeled as LC, SC and Ag-SC, respectively. The three heteroatom-doped carbon materials possessed extremely high cycling performance; after cycling for 50,000 times, the specific capacitances of LC and SC could maintain 119.8% and 96.0%, and the specific capacitance of Ag-SC could maintain 131.1% after cycling for 40,000 times. Additionally, the energy densities of the corresponding solid-state symmetric supercapacitors were 9.5, 6.2 and 6.9 Wh kg⁻¹ at the power density of about 900 W kg⁻¹, respectively, and the specific capacitances could retain 141.5%, 128.9% and 102.2% after 50,000 cycles.