Partially nitrogenized mesoporous Co3O4 nanoflakes as a binder-free positive electrode for high-performance flexible solid-state asymmetric supercapacitors

Abstract

Flexible energy storage and conversion devices have drawn intensive attention in wearable electronics. Herein, partially nitrogenized mesoporous Co3O4 nanoflakes were deposited on hydrophilic conductive carbon fabric (N-Co3O4@CF) through a simple two-step preparation method, involving the electrodeposition of the precursor and subsequent thermal annealing under controlled conditions. The binder-free N-Co3O4@CF material was designed to be and innovative positive electrode with a greatly enhanced capacity of 473.3 C g−1 owing to the changes in the electrical conductivity and electrochemical active sites caused by nitrogen introduction. Moreover, a flexible solid-state asymmetric supercapacitor (FSASC) combined with N-Co3O4@CF as the positive electrode and 3D interconnected Fe2O3 nanosheet networks (Fe2O3@CF) materials as the negative electrode was assembled. The fabricated FSASC achieved a high specific capacitance of 111.6 F g−1 and excellent cycling stability (93.8% capacitance retention after 10,000 cycles). In addition, the device exhibited exceptional flexibility and excellent mechanical stability after flexibility tests, including bending the FSASC at various bending angles (no significant change of the CV and GCD curves after bending 180°) and a 100-bending-cycle durability test (only 5% loss in capacitance after continuous bending). Finally, the FSASC device delivered a competitive energy density of 39.7 Wh kg−1 with the low-cost, lightweight and easy fabrication features, which may open up a promising opportunity for wearable energy storage device.