Supercapacitors Based on Mixed Nickel/Cobalt 2D MOF Coordination Nanosheets for Energy Storage

Three flexible coordination nanosheets, CoNi-nanosheet, Co-nanosheet, and Ni-nanosheet, were successfully synthesized using the liquid–liquid interfacial coordination method by the reaction of the ligand, 1,1,2,2-tetrakis(4-(2,2′:6′,2″-terpyridyl)phenyl)ethylene with nickel(II) and cobalt(II) nitrates. The effective coordination between the ligand and metal ions is confirmed using characterization techniques including Fourier transform infrared spectra, X-ray photoelectron spectroscopy, scanning electron microscopy, and atomic force microscopy. The bimetallic nanosheet, CoNi-nanosheet, demonstrates an exceptional specific capacity of 112.0 mA h g–1 at 1 A g–1. Furthermore, the CoNi-nanosheet maintains a capacity retention of 70.07% at 5 A g–1 after 1000 cycles. Upon integration into an asymmetric supercapacitor configuration, the CoNi-nanosheet assembly attains a heightened energy density of 89.0 W h kg–1 at a power density of 800 W kg–1. Impressively, the asymmetric supercapacitor has great stability. The excellent electrochemical performance of the bimetallic CoNi-nanosheet is likely attributed to alterations of electron densities around Co2+ and Ni2+ ions.