Advanced Cu_0.5Co_0.5Se₂ nanosheets and MXene electrodes for high-performance asymmetric supercapacitors

Transition-metal chalcogenides (TMCs) have attracted numerous interests in the field of energy storage owing to their exceptional electrical conductivity, ultrahigh specific capacity, etc. Herein, with inspiration from the attractive nanostructures of hierarchical frameworks with interconnected networks, we endeavored to design ternary copper cobalt selenide (Cu_xCo_1–xSe₂) nanostructures through a facile and cost-effective hydrothermal and followed by selenization process. The effects of Cu²⁺ is investigated and shows significant enhancement in the electrochemical performances. The optimal Cu_0.5Co_0.5Se₂ nanosheets (NSs) possess hierarchical architectures, large specific surface area, unique porous networks, and excellent intrinsic conductivity that result in superior electrochemical properties by their excellent synergistic effects. Taking advantage of the merits of the rational nanostructures, the Cu_0.5Co_0.5Se₂ NSs significantly boost the capacitive performances as ultrahigh specific capacitance of ~1695 F g⁻¹ at a current density of 1 A g⁻¹, and long-term cycling stability (~94.9%). An asymmetric supercapacitor (ASC) device is fabricated using the Cu_0.5Co_0.5Se₂ NSs as a positive electrode, and multilayered MXene (Ti₃C₂) as a negative electrode. Remarkably, the ASC operates at a working potential of 1.6 V and delivers a high energy density (~84.17 Wh kg⁻¹ at 0.604 kW kg⁻¹), high power density (~14.95 kW kg⁻¹ at 57.73 Wh kg⁻¹), and exceptional cycling stability (~91.1% after 10,000 charge–discharge cycles). The energy-storage properties are superior to recently reported TMCs-based ASC, proposing that the Cu_0.5Co_0.5Se₂//MXene ASC has massive potential for next-generation energy-storage systems.