Vertically Stacked Bilayer CuCo₂O₄/MnCo₂O₄ heterostructures on Functionalized Graphite Paper for High-Performance Electrochemical Capacitors

Abstract

Cobaltite system with spinel structures is a promising cathode material for next-generation high-performance electrochemical capacitor because of its high stability in electrochemistry. However, increasing the mass loading of active materials without sacrificing the geometry of the nanostructures remains a challenge. In this study, we propose vertically stacked bilayer spinel heterostructures constructed from hierarchical CuCo 2 O 4 /MnCo 2 O 4 on graphite paper as highly capable supercapacitor electrode. A two-step hydrothermal method with post annealing treatment is used in the preparation of heterostructures. CuCo 2 O 4 /MnCo 2 O 4 electrode delivers remarkable specific capacitance of 1434 F g −1 at 0.5 A g − 1 , considerable high-rate capability (810 F g −1 at 15 A g −1 ), and an excellent cycling stability maintaining 81.4% at 10 A g − 1 after 5000 cycles. An electrochemical capacitor device operating at 1.6 V is constructed using CuCo 2 O 4 /MnCo 2 O 4 and graphene as positive and negative electrodes, respectively. The device shows high energy density of 42.1 Wh kg −1 at a power density of 400 W kg −1 , as well as good cycling stability (88.4% retention after 10000 cycles). The stacking concept of heteronanostructures can potentially enrich the electrochemical performance of metal oxides for next-generation electrochemical capacitors. Figure 1