Surface Sulfurization and Self-Reconstruction Strategy for Decorating Carbon Nanofibers to Fabricate Sheet-Like NiCo2S4 Grown on Ni3S2 Electrode for High-Energy Density Asymmetric Supercapacitor

In this study, transition metal sulfide-based binder-free hybrid electrodes were grown in-situ on Ni foam using hydrothermal method. However, it still remains a challenge for designing a heterostructure with sufficient electroactive sites to improve electrochemical performance. Herein, effects of CNF@NSNCS on Ni foam binder-free composites were investigated for developing high-performance, low-cost supercapacitors. By avoiding the use of additive binding polymers, the purity of the electrodes was enhanced, resulting in excellent electrochemical behavior. The prepared binder-free CNF@NSNCS composite electrode exhibited an ultrahigh specific capacitance of 2739 F/g at a current density of 1 A/g, with superior capacitance retention charge-discharge cycle stability of 100 % over continuous 14,000 cycles at 10 A/g. Furthermore, an asymmetric supercapacitor (ASC) was assembled using CNF@NSNCS binder-free composites as the positive electrode and Activated carbon (AC) as the negative electrode. The assembled devices demonstrated superior electrochemical performance, delivering a high energy density of 77.5 Wh/kg at a power density of 748.4 W/kg. This work may contribute to advancing the development of low-cost, high-performance energy storage applications for the next generation of portable electronic devices.