Nickel and cobalt metal-organic-frameworks-derived hollow microspheres porous carbon assembled from nanorods and nanospheres for outstanding supercapacitors

The development of efficient electrode materials is essential to promote the performance of energy storage equipment. Nowadays, metal organic frameworks (MOFs) have been widely regarded as active materials for supercapacitors mainly thanks to their adjustable structure and outstanding porosity. Here, highly optimized Nickel and Cobalt MOF-derived N-doped porous carbon (Ni/Co-MOF-NPC) are considered the best choice for electrode materials due to their unique structural properties and excellent electrochemical performance. Pure cobalt oxide rarely reaches a specific capacitance of 104.3 F g-1 when the current density is 1 A g-1, but the optimized Ni/Co-MOF-NPC-2:1 offers an ultra-high specific capacitance of 1214 F g-1, which is much higher than that of pure cobalt oxide in a three-electrode test system. When the current density is 10 A g-1, after 6000 cycles, the capacitance can still maintain 98.8% of the initial capacitance. Asymmetric supercapacitors were assembled using the prepared Ni/Co-MOF-NPC-2:1 as the positive electrode material, corrugated paper activated carbon (CPAC) as the negative electrode material, the prepared Ni/Co-MOF-NPC-2:1//CPAC exhibits an outstanding energy density of 55.4 Wh kg-1 at 758.5 W kg-1, and has a significant cycle stability of 75.2% retention after 20,000 cycles. This excellent MOF synthesis strategy reduced the gap between the experimental synthesis and practical application of MOF in fast energy storage.