Flexible free-standing Ni-Mn oxides antennas decorated CNTs/nanofibers membrane for high- volumetric capacitance supercapacitors

There is a growing demand for lightweight flexible supercapacitors with high electrochemical performance for wearable and portable electronics. Here, we span nanoparticles of nickel -manganese oxide along with carbon nanotubes into carbon nanofibers and engineered a 3D networked Ni-Mn oxides /CNT@CNF free-standing membrane for flexible supercapacitor applications. The electrospinning process controlled the nanoparticles aggregation while subsequent heat treatment generates the nanochannels in the fibres, resulting a very porous tubular nano composite structure. The preparation process also enabled good interfacial contact between the nanoparticles and the conductive carbon network. The resulted Ni-Mn oxides /CNT@CNF membrane displays a high mass loading (Ni-Mn oxides) of 855 mg cm-3 and a minimum CNTs incorporation as ~ 0.4 %. The outstanding porous structure, synergy of the carbon with Ni-Mn oxides, fast and facile faradic reactions on the electrode were responsible for the superior volumetric capacitance of 250 F cm-3 at 1 A cm-3, energy density high as 22 mWh cm-3 and an excellent power density of 12 W cm-3. Despite the low CNT loading, the hybrid electrode exhibits excellent cycling performance with a capacitance retention of 96.4 % after 10000 cycles evidencing a well-preserved Ni-manganese oxides nano structure throughout the cycling. The resulted outstanding electrochemical performances of Ni-Mn oxides /CNT@CNF synergic system offer new insights into effective utilization of transition metal oxides for establishing high-performance flexible super capacitors within a confined volume.