Morphological modulation of cobalt selenide on carbon cloth by Ni doping for high-performance electrodes in supercapacitors

Transition metal selenides are desirable electrode materials in supercapacitors due to the good electron conductivity and high theoretical specific capacity. In this work, the relationship between the elemental composition and electrochemical performance of cobalt nickel selenide is studied. Cobalt nickel selenide samples with different morphologies are prepared on the carbon cloth by a solvothermal technique and selenation process using different Ni amounts. Ni doping is observed to modulate the morphology of CoSe₂ and enhance the electrochemical properties. The Co_0.8Ni_0.2Se₂ electrode shows a high specific capacitance of 1472 mF cm⁻² at a current density of 1 mA cm⁻² as well as good cycling stability. As a verification of the practicality, the asymmetrical supercapacitor assembled shows a capacity of 120 mF cm⁻² after 8000 cycles at 1 mA cm⁻² while delivering a superior power density 3.75 mW cm⁻² with an energy density of 0.052 mWh cm⁻². These results demonstrate the high potential of Co_0.8Ni_0.2Se₂ as electrode materials in supercapacitors.