Monolithic porous carbon membrane-based hybrid electrodes with ultrahigh mass loading carbon-encapsulated Co nanoparticles for high-performance supercapacitors

Abstract

Electrodes for commercially viable supercapacitors (SCs) require an active material mass loading of >10 mg cm⁻²; however, increasing the mass loading or electrode thickness typically deteriorates the electron and mass transfer and thus results in inferior specific capacitance, rate capability, and cycling stability. Herein, we develop a monolithic carbon membrane-based hybrid electrode (Co@CPE) with ultrahigh mass loading carbon-coated Co nanoparticles (>20 mg cm⁻²) by direct carbonization of Co²⁺-adsorbed Pleurotus eryngii (PE). During carbonization, the PE precursor is converted into a carbon membrane matrix with a layered porous structure, good conductivity and excellent structural integrity, whereas the adsorbed Co²⁺ ions are in situ converted into carbon-encapsulated Co nanoparticles that are firmly and evenly distributed on a carbon membrane matrix. The optimal Co@CPE-1000 electrode has a high areal capacitance of 5.04 F cm⁻² at 2 mA cm⁻². Due to the high mass loading, the symmetric SC assembled by the Co@CPE-1000 electrode has a high specific capacitance of 2.81 F cm⁻² at 2 mA cm⁻² and an energy density as high as 190 μW h cm⁻². Notably, the symmetric SC exhibits an ultra-long cycle life, with a retention rate of 113% after 40 000 cycles. This work presents a feasible and effective strategy for the development of monolithic carbon membrane-based hybrid electrodes with high active mass loading for achieving practically viable SCs with excellent electrochemical performance.