Rapid and simplistic microwave assisted method to synthesise cobalt selenide nanosheets; a prospective material for high performance hybrid supercapacitor

Metal selenides, particularly transition metal selenides, are the superb potential electrode materials for electrochemical energy storage applications. Herein, the cobalt selenide (Co_0.85Se) nanosheets are successfully synthesized by a rapid, simplistic, and economical technique via the microwave-assisted method. It is found that Co_0.85Se achieves the large specific surface area (104 m² g⁻¹), and delivers a higher specific capacitance (1580 F g⁻¹ at 1 A g⁻¹ and 500 F g⁻¹ at 20 A g⁻¹) as a positive electrode for hybrid supercapacitor. Further, a full-cell hybrid supercapacitor is assembled by using Co_0.85Se as an anode and activated carbon as the cathode, which shows excellent energy density 51.2 W h kg⁻¹ at power density 800 W kg⁻¹, and maintains 28.4 W h kg⁻¹ when power density increases to 12,800 W kg⁻¹. Moreover, the full-cell device shows remarkable stability of 10,000 cycles, having a wider operating potential window ranging from 0 to 1.6 V. Such excellent performance of Co_0.85Se exhibits that it is a favorable material for the energy storage applications.