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The rational design and construction of supercapacitor electrode materials with prominent energy and power density play an indispensable role for their potential application in energy storage devices. In this work, NiCo2O4 nanowires grown on Ni foam have been synthesized through a facile hydrothermal approach, revealing a large capacitance and superior cycling stability with 80.3% capacitance retention after 20 000 cycles. The asymmetric supercapacitors are fabricated based on NiCo2O4 nanowire electrodes, which deliver an energy density of 27.4 W h kg−1 at a power density of 493.2 W kg−1 and an excellent cycle life with 79.2% capacitance retention after 10 000 cycles. [ABSTRACT FROM AUTHOR]

Herein, we report a simple and facile sequential hydrothermal process for the synthesis of Co3O4 nanowire@NiO nanosheet arrays (CNAs). The as-synthesized CNAs were characterized in detail using various analytical techniques, which confirmed the high crystallinity, purity, and high-density growth of these nanomaterials. From an application point of view, the as-synthesized CNAs were directly used as supercapacitor electrodes, revealing a specific capacitance of up to 2018 mF cm−2 at a current density of 2 mA cm−2. Furthermore, a flexible asymmetric supercapacitor was fabricated using the as-synthesized CNAs as the anode and activated carbon as the cathode, which revealed a specific capacitance of 134.6 mF cm−2 at a current density of 2 mA cm−2. In addition, the supercapacitor showed excellent capacity retention of 73.5% after 10 000 cycles at a current density of 10 mA cm−2. [ABSTRACT FROM AUTHOR]