Facile synthesis of morphology-controlled hybrid structure of ZnCo₂O₄ nanosheets and nanowires for high-performance asymmetric supercapacitors

In the present study, two types of nanostructured electrodes consisting of ZnCo2O4 nanowire arrays (NWAs) and ZnCo2O4 nanosheet arrays (NSAs) were successfully synthesized through a facile hydrothermal method followed by an annealing treatment. The ZnCo2O4 NWAs electrode exhibited a high specific capacitance of 2049 F g(-1) at 2 mA cm(-2) and an excellent rate capability of 83.6% as the current density was increased from 2 to 30 mA cm(-2). Moreover, the cycling stability of ZnCo2O4 could retain 88.8% capacitance retention after 3000 cycles at a high current density of 10 mA cm(-2). The ZnCo2O4 NSAs delivered a specific capacitance of 1159 F g(-1) at 2 mA cm(-2) and a long-term cycling performance of 79.9% capacitance retention. An asymmetric supercapacitor (ASC) was assembled using ZCO-1 NWAs and activated carbon (AC) as the positive and negative electrodes, respectively, and the optimized ASC cell delivered a high energy density of 37.5 W h kg(-1) at a power density of 358.2 W kg(-1). The excellent electrochemical performance of ZnCo2O4 NWAs electrode implied that such electrode could be effectively used in supercapacitors (SCs).