High-performance aqueous asymmetric supercapacitor based on a composite cathode composed of MnCo2O4and CoMnP4

An electrode with a broad voltage window and a high areal/volumetric specific capacitance is crucial for a practical supercapacitor. Herein, we report a composite electrode with a high mass-loading of approximately 8.7 mg cm−2on Ni foam prepared by hydrothermal growth of MnCo2O4and the following electrochemical deposition of CoMnP4. The loose structure and synergistic effect of MnCo2O4and CoMnP4endow the electrode with a capacitance of 15.08 F cm−2(7.54C cm−2) at 1 mA cm−2, as well as good cycling stability and rate performance. The aqueous asymmetric supercapacitor with this cathode and the activated carbon anode has a broad voltage window of 0.0–1.7 V, high energy density of 0.756 mWh cm−2at 0.850 mW cm−2and outstanding cycling performance of 85.0 % capacitance retention with 100 % Coulombic efficiency over 20,000 cycles at 20 mA cm−2.