A new strategy for synthesis of hierarchical MnO2–Mn3O4 nanocomposite via reduction-induced exfoliation of MnO2 nanowires and its application in high-performance asymmetric supercapacitor

Abstract

The intrinsically low electrical conductivity and the poor cycling stability are two major obstacles of manganese oxides to hamper their further application in high-performance supercapacitors. One effective way to enhance their electrochemical properties is construction of appropriate nanocomposite with different structures. Herein, we demonstrated the fabrication of a hierarchical MnO2 nanowires-Mn3O4 nanoparticles nanocomposite by an effective and innovative two-step synthesis strategy. Further, the Mn3O4 nanoparticles were exfoliated from the surface of α-MnO2 nanowires. And the optimum composition was calculated to be ~35% Mn3O4 and ~65% α-MnO2. The capacitance of the optimized MnO2–Mn3O4 nanocomposite electrode reaches 278.2 F g−1 at a current density of 20 A g−1, and the capacitance retained at 99.3% even after 5000 cycles. The asymmetric supercapacitor was also fabricated with optimized MnO2–Mn3O4 as the positive electrode and activated carbon as the negative electrode. It could deliver an excellent energy density of ~41.3 Wh kg−1 at a power density of ~1153W kg−1. And the superior cycling stability achieves as well. The excellent capacitance properties of the MnO2–Mn3O4 nanocomposite can be attributed to the hybrid structure, in which one-dimension α-MnO2 nanowires provide a super highway for electron and ion transfer and Mn3O4 nanoparticles attached offer the abundant pseudocapacitive sites for charge storage.