Self-Assembly of Ni-Doped Co-MOF Spherical Shell Electrode for a High-Performance Supercapacitor

Bimetallic metal–organic frameworks (Bi-MOFs) have recently attracted increasing interest for use as electrode materials in energy storage devices due to their abundant active sites and porous structure. Here, we report our work on the self-assembly of Ni-doped Co-MOF (CoNix-MOF) spherical shell electrodes by CoNix-MOF nanosheets via a facile solvothermal process. At the optimized Ni doping value x = 0.5, the CoNi0.5-MOF electrode exhibits a high capacitance of 663.6 F g–1 at a current density of 1 A g–1 and a capacity retention rate over 96% after 10 000 cycles. Furthermore, the asymmetric solid-state supercapacitor (ASSC) constructed by using the CoNi0.5-MOF spherical shell cathode and N-doped graphene anode exhibits a high energy density of 23.44 Wh kg–1 at a power density of 350 W kg–1. The bimetallic Co, Ni and spherical shell structure self-assembled by the CoNi0.5-MOF nanosheets has been indicated to be very effective for providing a large number of active sites and promoting the transport of electrolyte ions. The results have shown great potential to promote the practical application of Bi-MOFs in supercapacitors.