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

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 MnO 2 nanowires-Mn 3 O 4 nanoparticles nanocomposite by an effective and innovative two-step synthesis strategy. Further, the Mn 3 O 4 nanoparticles were exfoliated from the surface of α -MnO 2 nanowires . And the optimum composition was calculated to be ~ 35% Mn 3 O 4 and ~ 65% α -MnO 2 . The capacitance of the optimized MnO 2 –Mn 3 O 4 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 MnO 2 –Mn 3 O 4 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 MnO 2 –Mn 3 O 4 nanocomposite can be attributed to the hybrid structure, in which one-dimension α -MnO 2 nanowires provide a super highway for electron and ion transfer and Mn 3 O 4 nanoparticles attached offer the abundant pseudocapacitive sites for charge storage.