Mechanochemical production of graphene/amorphous carbon/Mn3O4 nanocomposites for asymmetric supercapacitor

Abstract

The practical application of graphene/manganese oxide nanocomposites in energy storage presents a significant challenge due to their environmentally unfriendly and complex synthesis, as well as weak interface interactions. Herein, a sustainable and scalable ball milling-thermal annealing method is proposed to produce a graphene/amorphous carbon/Mn3O4 (GACMO) nanocomposite. A triblock copolymer is employed as an intercalator to facilitate the formation of few-layer graphene during ball-milling, a precursor for amorphous carbon to encapsulate Mn3O4 upon thermal-annealing, and thus an intermediate layer to enhance the interface interaction between graphene and Mn3O4. Benefiting from its 3D porous structure and exceptional interface design, GACMO exhibits a large specific surface area, excellent electrical conductivity, enhanced structural stability. Consequently, the GACMO electrode presents a high capacitance of 219 F g−1 at 0.5 A g−1 with a 91.4 % retention at 10 A g−1 after 5000 cycles. Furthermore, the GACMO-based asymmetric supercapacitor shows a high capacitance of 138 F g−1 at 0.5 A g−1, superior energy/power density (62.1 W h kg−1 at 0.45 kW kg−1, 0.6 mW h cm−3 at 9.3 mW cm−3), and promising cycling stability (88.3 % retention after 10,000 cycles). This study brings new insights into the fabrication of graphene/metal oxide-based energy materials.