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Freestanding porous Co₉S₈ nanoneedle bundles arrays on Ni foam were in-situ synthesized by a facile ion exchange reaction and were directly used as the electrode for supercapacitors. The structure and morphology were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscope (TEM). Cyclic voltammetry (CV), chronopotentiometry (CP) and electrochemical impedance spectroscopy (EIS) were adopted to evaluate the electrochemical property of the porous Co₉S₈ nanoneedle bundles arrays electrode in 3M KOH solution. The specific capacitance of the porous Co₉S₈ nanoneedle bundles arrays was 1400 F g_-1 at a current density of 4 A g_-1 and exhibited good cycling stability. The excellent electrochemical performance can be ascribed to the porous nanostructure of Co₉S₈ nanoneedle bundles arrays and the 3D conductive nickel foam, which can increase the contact areas between electrode and electrolyte and improve the conductivity of the whole electrode.