Manganese Monoxide/Biomass-Inherited Porous Carbon Nanostructure Composite Based on the High Water-Absorbent Agaric for Asymmetric Supercapacitor

Biomass-inherited metal oxide/carbon composites have been utilized as competitive materials of supercapacitor electrodes owing to the hierarchical structures, fast regeneration rate, and easy synthesis. However, the low content and agglomeration of metal oxides are the contradictory issues to be addressed for their practical applications. In this work, manganese monoxide/biomass-inherited porous carbon (MnO/BPC) nanostructure composites with high MnO content (∼75%) and uniform distribution have been prepared through a simple immersion-calcination process by high water-absorbent agaric. The superhigh Mn2+ solution absorption of agaric ensures the high MnO content in MnO/BPC composite, and the abundant internal chitin with hydrogel and hot-melting property enables the uniform dispersion of MnO in carbon matrix. The carbon nanostructure endows the composite with high specific surface area, efficient electron/ion transportation, and better electrolyte wettability. As expected, the MnO/BPC composite materials realizes high capacitance of ∼735 mF cm–2 (∼637 F g–1) at 3 mA cm–2, good rate performance (∼608 mF cm–2 at 10 mA cm–2), and excellent cycling performance (capacity retention of ∼91% at 10 mA cm–2, 5000 cycles). In addition, this work presents a facile and productive strategy to obtain metal-based composites with high metal-oxide content and homogeneous distribution by adopting the edible and worldwide abundant agaric.