MXene-modulated CoNi2S4 dendrite as enhanced electrode for hybrid supercapacitors

Bimetallic transition metal sulfides (TMSs) and MXene are the two kinds of promising candidates as electrode materials for supercapacitors based on different storage mechanisms. However, little work has been performed on their composites. In this paper, Ti 3 C 2 MXene-wrapped CoNi 2 S 4 nanotrees were synthesized controllably using flake ZIF-67 as precursor grown on nickel foam, which was transformed into dendrite CoNi 2 S 4 dendrite in MXene suspension (weak acidic environment). The formation mechanism of CoNi 2 S 4 dendrite was discussed. Ti 3 C 2 MXene-wrapped CoNi 2 S 4 nanotrees delivered very high specific capacity of 933 C g −1 at 1 A g −1 and good rate performance. This is due to that the unique dendrite morphology can provide many exposed electro-active sites and wrapped conductive MXene can facilitate the charge transfer. An asymmetric supercapacitor was assembled using CoNi 2 S 4 /MXene/NF and RGO as positive and negative electrodes, which delivered a high energy density of 30.5 Wh kg −1 without deteriorating its high power density (1587 W kg −1 ). This device can power the clock for 55 minutes, demonstrating its broad practical application potential.