Indirect Nanoconstruction Morphology of Ni₃S₂ Electrodes Renovates the Performance for Electrochemical Energy Storage

Asymmetric supercapacitors with positive electrodes based on transition metal sulfides show high specific capacitance with higher energy density than that of carbon-based supercapacitors, which suffer from low electrochemical stability because of poor conductivity of the electroactive materials and high reliance on faradaic redox reactions. In this work, the unfavorable redox reaction kinetics of nickel sulfides (Ni₃S₂) is compensated by fabricating a highly porous Ni current collector. The as-prepared Ni₃S₂ electrodes show a high specific capacity of 786.5 C g^–1 at a current density of 10 mA cm^–2 with high rate capability due to their continuous electronic conduction channels supported by the porous Ni frame. An asymmetric full-cell supercapacitor is fabricated using Ni₃S₂ as a positive electrode and activated carbon (AC) as a negative electrode, showing a high energy density of 39.7 W h kg^–1 at a power density of 833 W kg^–1. Moreover, a 93.9% specific capacitance is retained even after 6000 cycles, indicating the excellent stability of the cell.