Improved electrochemical performance of sandwich-structured N-rich C@MnO₂@C electrodes

This paper reports the capacitive behavior of N-enriched carbon nanofiber/MnO2/carbon nanofibers with a triple layer structure (N-rich C@MnO2@C) prepared by continuous electrospinning. N-functional groups were intro-duced into the upper (or lower) or middle layer of the triplex and the structures and electrochemical properties of each are compared. N-functional groups introduced into the lower (or upper) layer induce a high surface area, numerous pyrrolic-N, high electrical conductivity, and low contact angle in N-rich C@MnO2@C composites. The optimized material provides a specific capacitance of 201 Fg(- 1) (1 mAcm(-2)) with more than 84% specific capacitance retention in a symmetric two-electrode cell configuration using a 6 M KOH electrolyte. In addition, it shows a maximum energy density of 24.8 and 13.41 Whkg (-1) at power densities of 400 and 10,000 Wkg(-1) with excellent cycling stability (95% capacity retention after 10,000 cycles at 1 mAcm(- 2)). An assembled asymmetric device, consisting of optimized N-rich C@MnO2@C as the positive electrode and C@MnO2@C as a negative electrode, delivers a high energy density of 41 Whkg(-1) at a power density of 400 Wkg(-1). This material has excellent potential as an electrode for constructing high-voltage asymmetric supercapacitors in aqueous electrolytes.