Low crystalline CoSx was fabricated by anion-exchange of 2-dimensional (2D) cobalt carbonate hydroxide (CoCH) using aqueous sodium sulfide solution at room temperature. It was proved that single crystalline CoCH nanoplates would transform into porous 2D CoSx with low crystallinity after the anion-exchange. When they were used as electrode materials for supercapacitor, the 2D CoSx material had a much higher specific capacitance than its precursor due to their different compositions and electroconductivities. CoSx had a high specific capacitance of 863 F g−1 at 1 A g−1 and a good stability during long time charge-discharge processes, about 64.7% of initial capacitance retention after 10000 cycles. Asymmetric hybrid devices using 2D CoSx as positive electrode and activated carbon as negative electrode were assembled, and the capacitor devices were able to achieve a high energy density of 33.56 Wh kg−1 at the power density of 400 W kg−1. The high performances of the porous CoSx make it a promising electrode material for energy storage.