Ultrahigh-areal-capacitance aqueous supercapacitors enabled by soft biomass-derived porous carbon membrane

Sustainable biomass-derived carbons in powdery forms have shown to be high-performance capacitive electrode materials for application in supercapacitors (SCs) due to their large specific surface area, distinct porous structure, and low cost; however, their practical applications are being largely hampered due to their powdery status-related issues including tedious electrode assembly process and insufficient capacitance and cycling stability. Herein, we develop a porous carbon membrane, termed as PECM, by direct carbonization of Pleurotus eryngii (PE) using KOH as activator. The as-fabricated PECM features a hierarchically nanostructure with high porosity, large specific surface area, and excellent electrolyte wettability, which cannot only afford a large usable active area for the interfacial adsorption of electrolyte ions but also supply fast diffusion pathways for electrolyte ions. Moreover, the as-fabricated PECM is doped with N and also has large amounts of O, S, and P-containing functional groups, which would be expected to contribute additional pseudocapacitance. More importantly, the as-fabricated PECM has excellent mechanical performance and can be directly used to assembly an aqueous symmetric SC device. Attributing to the above structural merits of PECM, the two-electrode symmetric SC assembled using two identical PECM-800 electrodes (similar to 20 mg cm(-2) for each electrode), exhibits excellent electrochemical performance with ultrahigh areal capacitance (4.6 F cm(-2) at 10 mA cm(-2)), excellent long-term cycling stability (113% capacitance retention after 20 000 cycles), and superior energy densities of 0.24 to 0.09 mWh cm(-2) at power densities of 5.20 to 51.9 mW cm(-2). This work offers a new insight on employing biomass to prepare value-added and practically applicable carbon materials for the application in SCs.

Automated summary

The porous carbon membrane PECM prepared by direct carbonization of Pleurotus eryngii shows excellent electrochemical performance and can be directly used for supercapacitor assembly, exhibiting high capacitance and cycling stability. This offers new insights into utilizing biomass for the preparation of value-added carbon materials for supercapacitor applications.