Hierarchical coral-like MnCo2O4.5@Co-Ni LDH composites on Ni foam as promising electrodes for high-performance supercapacitor.

Transition metal oxides are generally designed as hybrid nanostructures with high performance for supercapacitors by enjoying the advantages of various electroactive materials. In this paper, a convenient and efficient route had been proposed to prepare hierarchical coral-like MnCo2O4.5@Co-Ni LDH composites on Ni foam, in which MnCo2O4.5nanowires were enlaced with ultrathin Co-Ni layered double hydroxides nanosheets to achieve high capacity electrodes for supercapacitors. Due to the synergistic effect of shell Co-Ni LDH and core MnCo2O4.5, the outstanding electrochemical performance in three-electrode configuration was triggered (high area capacitance of 5.08 F cm-2at 3 mA cm-2and excellent rate capability of maintaining 61.69% at 20 mA cm-2), which is superior to those of MnCo2O4.5, Co-Ni LDH and other metal oxides based composites reported. Meanwhile, the as-prepared hierarchical MnCo2O4.5@Co-Ni LDH electrode delivered improved electrical conductivity than that of pristine MnCo2O4.5. Furthermore, the as-constructed asymmetric supercapacitor using MnCo2O4.5@Co-Ni LDH as positive and activated carbon as negative electrode presented a rather high energy density of 220µWh cm-2at 2400µW cm-2and extraordinary cycling durability with the 100.0% capacitance retention over 8000 cycles at 20 mA cm-2, demonstrating the best electrochemical performance compared to other asymmetric supercapacitors using metal oxides based composites as positive electrode material. It can be expected that the obtained MnCo2O4.5@Co-Ni LDH could be used as the high performance and cost-effective electrode in supercapacitors.

Three-dimensional hierarchical core-shell CuCo2O4@Co(OH)2 nanoflakes as high-performance electrode materials for flexible supercapacitors.

Rational design of composite electrode materials with novel nanostructures plays an important role in improving both high energy density and structure stability of flexible and wearable supercapacitors. Herein, numerous peculiar three-dimensional hierarchical core-shell CuCo2O4@Co(OH)2 nanoflakes directly grown on Ni foam are synthesized via a facile hydrothermal method and subsequent electrodeposition technique. Ultrathin Co(OH)2 nanosheets arrays vertically anchored on CuCo2O4 nanoflakes can not only improve the electrical conductivity, but also provide interconnected channels for ion diffusion and enrich electrochemical active sites to boost faradaic redox reaction, leading to the enhanced electrochemical behavior. Excellent electrochemical performance of CuCo2O4@Co(OH)2 electrode can be reflected on a higher specific capacitance of 1558 F/g and lower resistance compared with that of the pristine CuCo2O4 electrode. The asymmetric flexible supercapacitor assembled by the optimized CuCo2O4@Co(OH)2 electrode and activated carbon exhibits high energy density of 62.5 Wh/kg at 893 W/kg, outstanding cycle stability of 88.6% capacitance retention after 10,000 cycles and remarkable mechanical flexibility, performing the best electrochemical behavior among various metal oxides based asymmetric supercapacitors. All above results indicate that the resulted hierarchical core-shell CuCo2O4@Co(OH)2 electrode can be a promising candidate for flexible energy storage devices.