3D hierarchical transition-metal sulfides deposited on MXene as binder-free electrode for high-performance supercapacitors

MXene has been considered as a promising two-dimensional material for supercapacitors owing to its large surface area , high conductivity, and excellent cycling stability. However, its low specific capacitance restricts its extensive applications. Therefore, to address the issue, we homogeneously deposited NiCo 2 S 4 nanoflakes on the surface of MXene on conductive nickel foam (denoted as MXene-NiCo 2 S 4 @NF), which was used as a composite binder-free electrode for supercapacitor applications. The NiCo 2 S 4 nanoflakes increased the surface area of the composite electrode, thereby increasing its specific capacity from 106.34 C g −1 to 596.69 C g −1 at 1 A g −1 . Compared to the pristine MXene, MXene-NiCo 2 S 4 @NF maintained the high retention rate of pristine MXene and exhibited excellent cycling stability with 80.4% of its initial specific capacity after 3000 cycles. The composite electrode exhibited improved electrochemical performance for supercapacitors , owing to the combined merits of NiCo 2 S 4 (high specific capacity) and MXene (high retention rate and good cycling stability. The fabricated asymmetric solid-state supercapacitor using MXene-NiCo 2 S 4 as a positive electrode and active carbon as a negative electrode, exhibited an energy density of 27.24 Wh kg −1 at 0.48 kW kg −1 of power density.