Construction of Ti₃C₂T MXene wrapped urchin-like CuCo₂S₄ microspheres for high-performance asymmetric supercapacitors

Copper cobalt sulfide (CuCo₂S₄) nanomaterials are regarded as promising electrode materials for high-performance supercapacitors due to their abundant redox states and considerable theoretical capacities. However, the intrinsic poor electrical conductivity, sluggish reaction kinetics and insufficient number of electroactive sites of these materials are huge barriers to realize their practical applications. In this study, a facile two-step strategy to engineer a hierarchical 3D porous CuCo₂S₄/MXene composite electrode is presented for enhanced storage properties. This well-constructed CuCo₂S₄/MXene composite not only provides abundant active sites for the faradaic reaction, but also offers more efficient pathways for rapid electron/ion transport and restricts the volumetric expansion during the charge/discharge process. When evaluated in a 3 M KOH electrolyte, the CuCo₂S₄/MXene-3 electrode exhibits a specific capacity of 1351.6 C g^-1 at 1 A g^-1 while retaining excellent cycling stability (95.2% capacity retention at 6 A g^-1 after 10 000 cycles). Additionally, the solid-state asymmetric supercapacitor (ASC) CuCo₂S₄/MXene//AC device displays an energy density of 78.1 W h kg^-1 and a power density of 800.7 W kg^-1. Two ASC devices connected in series can illuminate a blue LED indicator for more than 20 min, demonstrating promising prospects for practical applications. These electrochemical properties indicate that the high-performance CuCo₂S₄/MXene composites are promising electrode materials for advanced asymmetric supercapacitors.