Enhancing the Performance of a Battery–Supercapacitor Hybrid Energy Device Through Narrowing the Capacitance Difference Between Two Electrodes via the Utilization of 2D MOF-Nanosheet-Derived Ni@Nitrogen-Doped-Carbon Core–Shell Rings as Both Negative and Positive Electrodes

) has been proposed. Nickel/nitrogen codoped carbon (Ni@NC) materials, serving as positive electrodes, deliver battery-type behavior with the enhancement of capacities, which are even superior to those of pristine carbon-based materials with large surface areas. Meanwhile, HCl-treated Ni@NC materials (named A-Ni@NC) are employed as negative electrodes within the potential window of -1 to 0 V and exhibit higher capacitances than that of the commercial activated carbon. With Ni@NC and A-Ni@NC as positive and negative electrodes in BSH devices, the as-fabricated cells display higher capacities and energy densities, more excellent cycling stability, and far superior capacity retention in comparison with those of Ni@NC//AC cells. These results clearly confirm that our strategy is successful and effective.