Synthesis of ZnFe2O4@MnO2 Multilevel Nanosheets Structure and Its Electrochemical Properties as Positive Electrodes for Asymmetric Supercapacitors

ZnFe2O4@MnO2 was synthesized by a facile hydrothermal method. The morphology of ZnFe2O4@MnO2 was studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). SEM and TEM photographs showed that the structure of manganese dioxide was affected by the reaction time. The composition of this compound was investigated by XRD and XPS. Electrochemical tests showed that ZnFe2O4@MnO2 had more desirable electrical properties than ZnFe2O4, and the areal capacitance was 1442Fg(-1) at 2mAcm(-2). It also showed that ZnFe2O4@MnO2 possessed superior stability (90%remained after 3000 cycles). Activated carbon and ZnFe2O4@MnO2 were used to form the negative and positive electrodes of an asymmetric supercapacitor, respectively. The asymmetric supercapacitor had an energy density and power density of 49.7Wh kg(-1) and 1918.4W kg(-1), respectively.