Tetragonal CoMn₂O₄ nanocrystals on electrospun carbon fibers as high-performance battery-type supercapacitor...

We herein report a simple two-step procedure for fabricating tetragonal CoMn₂O₄ spinel nanocrystals on carbon fibers. The battery-type behavior of these composite fibers arises from the redox activity of CoMn₂O₄ in an alkaline aqueous solution, which, in combination with the carbon fibers, endows good electrochemical performance and long-term stability. The C@CoMn₂O₄ electrode exhibited high specific capacity, up to 62 mA h g^-1 at 1 A g^-1 with a capacity retention of around 90% after 4000 cycles. A symmetrical coin-cell device assembled with the composite electrodes delivered a high energy density of 7.3 W h kg^-1 at a power density of 0.1 kW kg^-1, which is around 13 times higher than that of bare carbon electrodes. The coin cell was cycled for 5000 cycles with 96.3% capacitance retention, at a voltage of up to 0.8 V, demonstrating excellent cycling stability.