CuMnO2-reduced graphene oxide nanocomposite as a free-standing electrode for high-performance supercapacitors

Free-standing electrodes have attracted wide attention for advanced supercapacitors. Herein, direct deposition of CuMnO2 and CuMnO2-reduced graphene oxide (rGO) nanocomposite on nickel foam (NF) substrates was performed through a simple hydrothermal process. The simultaneous deposition makes full use of the synergistic effect formed by the large pseudocapacitance of CuMnO2 and excellent electrical conductivity of rGO, which results a greater performance improvement of the nanocomposite comparing with that of bare CuMnO2. Remarkably, the CuMnO2-rGO/NF electrode displays a large specific capacitance of 1727 F g(-1) at 3 A g(-1) and manifests exceptional cycling stability with a retention ratio of 125% of the initial capacitance over consecutive 5000 cycles. Furthermore, a rGO/NF//CuMnO2-rGO/NF asymmetric supercapacitor exhibits great electrochemical performance by delivering high energy density (37.5 Wh kg(-1)) and high power density (4250 W kg(-1)) as well as excellent cycling stability (3.3% decay after 4000 cycles). The presented results suggest that CuMnO2-rGO nanocomposite can be considered as a potential candidate for highly stable and high-rate supercapacitors.