Design and Synthesis of CuCo ₂ O ₄ Microflowers @ MnO ₂ Nanosheets Hierarchical Structures for High‐Performance Supercapacitors

ABSTRACT The abundant active sites, high theoretical capacitance, and cost‐effective synthesis of AB 2 O 4 @MO 2 core‐shell heterostructures is crucial for enhancing the energy density and long‐term stability of asymmetric supercapacitors. Herein, a simple and facile two‐step solvothermal method was developed to synthesize CuCo 2 O 4 microflowers@MnO 2 nanosheets core/shell hierarchical structures (CuCo 2 O 4 @MnO 2 ) without post heat treating. The unique superstructures with MnO 2 nanosheets were grown on CuCo 2 O 4 microflowers not only inherited the individual advantages for supercapacitor electrode apply, but also provided synergistic effect of different component to optimize the electrode's properties. As a result, the CuCo 2 O 4 @MnO 2 electrode exhibited a high specific capacitance of 621.2 F g −1 at the current density of 1 A g −1 with excellent rate capability and remarkable cycling stability (retention of 88.8% after 10 000 cycles at a current density of 3 A g −1 ). Impressively, the optimized CuCo 2 O 4 @MnO 2 //AC ACS cell can be cycled reversibly in a wide voltage region as high as 1.6 V and exhibited a specific capacitance of 53.8 F g −1 at a current density of 0.5 A g −1 with a maximum energy density of 19.12 Wh kg −1 . These results demonstrated that constructing such unique CuCo 2 O 4 @MnO 2 hierarchical structures can be considered as an efficient method to enhance the performance of supercapacitor.