Fabrication and the electrochemical activation of network-like MnO2 nanoflakes as a flexible and large-area supercapacitor electrode

Porous network-like MnO2 thick films are successfully synthesized on a flexible stainless steel (SS) mesh using a simple and low-cost electrodeposition method followed by an electrochemical activation process. Morphology, chemical composition, and crystal structure of the prepared electrodes before and after the activation process are determined and compared by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) analyses. The results show that the implementation of the electrochemical activation process does not change the chemical composition and crystal structure of the films, but it influences the surface morphology of the MnO2 thick layer to a flaky nanostructure. Based on the electrochemical data analysis, the maximum specific capacitance of 1400mF (381Fg(-1)) and 3700mF (352Fg(-1)) are measured for small (2.6cm(2)) and large (10cm(2)) surface area electrodes, respectively. In addition, a flexible symmetric MnO2//MnO2 solid-state supercapacitor shows a capacitance of 0.3F with about 98% retention at different bending angles from 0 to 360 degrees.