Hierarchical structure ZnCo2O4/ZnCo2O4/CoO@rGO/GO as cathode material to construct high energy density supercapacitor

Abstract

With the energy crisis and environmental problems increasingly intensified, traditional energy can no longer meet the requirements of the new era. Therefore, supercapacitors have become popular energy storage devices because of their excellent performance. However, its low energy density limits its application scenarios. Here, we propose a composite material of ZnCo2O4/ZnCo2O4/CoO@rGO/GO (ZCG-2) with a hierarchical structure synthesized by a simple hydrothermal method as a cathode material for asymmetric supercapacitors. The material mainly uses the different structures of the same ZnCo2O4 material to form a hierarchical structure, thereby reducing the introduction of excessive elements. The specific capacitance is 1255.0 F g−1 at 1 A g−1. The asymmetric supercapacitor is prepared with ZCG-2 as positive electrode and activated carbon (AC) as negative electrode, which has a specific capacitance of 238.8 F g−1 at 1 A g−1, and a capacity retention rate of 85.5% after 10,000 cycles. More importantly, at a power density of 800 W kg−1, it has a specific energy as high as 84.9 Wh kg−1. This proves that the composite material obtained by this strategy has certain application potential in the field of electrochemical energy storage.