• Co 3 O 4 /Nitrogen-doped carbon (Co 3 O 4 /NC) composite was successfully prepared by a two-step calcination method with ZIF-67 as precursor. • The specific capacitance of Co 3 O 4 /NC at a current density of 1 A g−1 is 1144F g−1. • The Co 3 O 4 /NC//AC two-electrode capacitor generates the highest energy density of 40 Wh kg−1 at a power density of 1037 W kg−1. Metal-organic frameworks with high specific surface area and controlled morphology have great potential for lithium-ion battery applications. Here, the ZIF-67 precursor was prepared by the room temperature stirring method. Then Co 3 O 4 /NC composite electrodes with hollow polyhedral structure were successfully prepared by a two-step calcination method, and their electrochemical properties were discussed. The specific capacitance of Co 3 O 4 /NC at a current density of 1 A g−1 is 1144F g−1 (much higher than the specific capacitance of pure Co 3 O 4), and the retention rate is 45.4 % under a 20 A g−1 of current density. In addition, the asymmetric supercapacitor (ASC) device consisting of Co 3 O 4 /NC composite electrodes and activated carbon produced the highest energy density of 40 Wh kg−1 at a power density of 1037 W kg−1. At a current density of 5 A g−1, the capacitor retains 87.6 % of its initial capacitance after 10,000 charge/discharge cycles. [ABSTRACT FROM AUTHOR]