High performance asymmetric supercapacitor based on Cobalt Nickle Iron-layered double hydroxide/carbon nanofibres and...

A novel Cobalt Nickle Iron-layered double hydroxide/carbon nanofibres (CoNiFe-LDH/CNFs-0.5) composite was successfully fabricated through an easy in situ growth approach. The morphology and composition of the obtained materials were systematically investigated. When the two derived materials were used for supercapacitor electrodes, the CoNiFe-LDH/CNFs-0.5 composite displayed high specific surface area (114.2 m² g^-1), specific capacitance (1203 F g^-1 at 1 A g^-1) and rate capability (77.1% from 1 A g^-1 to 10 A g^-1), which were considerably higher than those of pure CoNiFe-LDH. Moreover, the specific capacitance of CoNiFe-LDH/CNFs-0.5 composite remained at 94.4% after 1000 cycles at 20 A g^-1, suggesting excellent long-time cycle life. The asymmetric supercapacitor based on CoNiFe-LDH/CNFs-0.5 as a positive electrode and activated carbon as a negative electrode was manufactured and it exhibited a specific capacitance of 84.9 F g^-1 at 1 A g^-1 and a high energy density of 30.2 W h kg^-1. More importantly, this device showed long-term cycling stability, with 82.7% capacity retention after 2000 cycles at 10 A g^-1. Thus, this composite with outstanding electrochemical performance could be a promising electrode material for supercapacitors.