Facile synthesis of hierarchical MnO2 sub-microspheres composed of nanosheets and their application for supercapacitors

Abstract

Hierarchical MnO₂ sub-microspheres were fabricated by using a simple, green and efficient low-temperature route. These sub-microspheres were formed via the aggregation of ultrathin nanosheets with a thickness of 2–4 nm. An electrode made of hierarchical MnO₂ sub-microspheres exhibited a specific capacitance of 120 F g⁻¹ at a current density of 0.167 A g⁻¹. For an asymmetric AC//MnO₂ supercapacitor, it exhibited a superior electrochemical stability in 1 M Na₂SO₄ aqueous solution with 88% retention of the initial specific capacitance after 1000 cycles, and the Coulombic efficiency was above 97%, indicating good charge–discharge reversibility and electrochemical stability.