A one-step solvothermal process is developed to synthesize novel CoNi₂S₄ nanoparticles. When applied as electrode materials of supercapacitors, CoNi₂S₄ nanoparticles with lower cost of production exhibit better electrochemical performances, i.e.: higher specific capacitance, better rate capability, and higher energy density which make it a promising electrode candidate material for next generation supercapacitors.