Challenges remain to show good capacitive performance while achieving high loadings of active materials for supercapacitors. Trying to realize this version, a nickel-protecting carbon fiber paper@Co-doped NiSx (Ni-CP@Co-NiSx) electrode with high specific gravimetric, areal, and volumetric capacitance is reported in this work. This free-standing electrode is prepared by an electroplating-hydrothermal-electroplating (EHE) three-step method to achieve a high loading of almost 26.7 mg cm-2. The cobalt-doping and nickel-protection strategies effectively decrease the impedance and inhibit the active material dropping from the electrode resulting from the expansion stress, which endows the Ni-CP@Co-NiSx electrode with a high rate and good cycling performance, especially with an ultrahigh specific areal/volumetric/gravimetric capacitance of 53.3 F cm-2/2807 F cm-3/1997 F g-1 at 5 mA cm-2, respectively. Employing activated carbon functionalized with riboflavin (AC/VB2) as a negative electrode, the asymmetric supercapacitor device delivers a very high energy density of up to 60.4 W h kg-1. This work demonstrates that electrodes with a high loading density and excellent performance can be obtained by the combination of the EHE method to adjust the internal conductivity and external structural stability.
Keywords: NiSx; asymmetric supercapacitor; cobalt-doped; high loading; nickel-protected.