Asymmetric supercapacitors based on high capacitance Ni6MnO8 and graphene

摘要

Supercapacitors with high energy density and high power density have attracted numerous attentions. Here, we successfully synthesized Ni6MnO8 material by a fast, facile, and cost-effective method, which the area specific capacitance was found to be as high as 1113 mF/cm^2 at a current density of 1 mA/cm^2. Further, the asymmetric supercapacitor was assembled by using Ni6MnO8 as the positive electrode and graphene as the negative electrode with an operation potential from 0 to 1.4 V. It exhibited an area specific capacitance of 69.1m F/cm^2 at 0.5 mA/cm^2 and stable cycling performance which presented about 80% capacitance retention after 5000 cycles at 5 mA/cm^2. The energy density of graphene//Ni6MnO8 supercapacitors was calculated to be 18.81 mWh/cm^2 at a power density of 350.1 mW/cm^2 and still remained 5.8 mWh/cm^2 at a power density of 6990.7 mW/cm^2, meaning that the asymmetric supercapacitor combine excellent power density and energy density.