Hierarchical core–shell heterostructure of porous carbon nanofiber@ZnCo2O4 nanoneedle arrays: advanced binder-free electrodes for all-solid-state supercapacitors†
Hierarchical ZnCo2O4 nanoneedle arrays are vertically grown on porous carbon nanofibers (PCFs) to form a core–shell heterostructure through a facile hydrothermal method followed by thermal treatment. Such a unique configuration makes full use of the synergistic effects from both excellent electrical conductivity of PCFs and high specific capacitance of ZnCo2O4, endowing the hybrid to be an excellent electrode for flexible supercapacitors. Benefiting from their intriguing structural features, the PCF@ZnCo2O4 hybrid possesses fascinating electrochemical performance as an integrated binder-free electrode for supercapacitors. Remarkably, this PCF@ZnCo2O4 electrode could achieve a high capacitance of 1384 F g−1 at a scan rate of 2 mV s−1. Moreover, an all-solid-state asymmetric supercapacitor fabricated with the as-prepared PCF@ZnCo2O4 hybrid as the positive electrode and PCFs as the negative electrode achieves a high energy density of 49.5 W h kg−1 (based on the total mass of the material on the two electrodes) at a power density of 222.7 W kg−1. Furthermore, the all-solid-state asymmetric supercapacitor device exhibits remarkable cycling stability with 90% specific capacitance retention after 3000 cycles. Therefore, these fascinating electrochemical performances make this material hold great promise for next-generation high-energy supercapacitor applications.