Exploring the electrochemical properties of CuSe-decorated NiSe₂ nanocubes for battery-supercapacitor hybrid devices

Chalcogenides, a promising class of electrode materials, attracted massive popularity owing to their exciting features of high conductive nature, high capacity, rich redox activities, and structural functionalities, making them the first choice for the electrochemical energy domain. This paper reported a new NiSe₂-CuSe nanocomposite prepared via a wet-chemical synthesis followed by a low-cost and simple hydrothermal reaction. The physical characterization showed cubes and nanoparticles type morphological features of NiSe₂ and CuSe products, while their composite reveals a combined morphological characteristic. The electrochemical properties were tested in an aqueous solution, demonstrating that the NiSe₂-CuSe nanocomposite exhibits a high capacity of 376 C g^-1, low resistance, good reversibility and rate capability in a three-electrode mode than bulk counterparts. For practical aspects, a battery-hybrid supercapacitor (BHSC) is developed with NiSe₂-CuSe nanocomposite, and activated carbon (AC) serves as cathode and anode in two-cell mode operation. The built NiSe₂-CuSe||AC/KOH BHSC expanded the voltage to 1.8 V and delivered the highest capacitance of 148 F g^-1 and 55 F g^-1 from 1 to 10 A g^-1, suppressing most of the previously existing literature reports. Also, our built NiSe₂-CuSe||AC/KOH BHSC displayed a high-power delivery of 8928 W kg^-1 at a maximum energy density of 66.6 W h kg^-1 and retained 91.7% capacitance after a long way of 10,000 cycles. These outstanding results demonstrate that metal selenides can be effectively utilized as alternative electrodes with high energy, rate performance, and long-term durability for advanced energy conversion and storage devices.