Dodecahedral NC-doped CoSe2 nanoparticles with excellent stability for high-performance flexible solid-state supercapacitors

In this study, CoSe₂/NC composites with stable dodecahedral structures were prepared by a simple one-step carbonization-selenization method using ZIF-67 as the precursor, and the effect of annealing time on their morphology and properties was investigated. SEM and TEM characterization results showed that the material with an annealing time of 1 h had the most stable framework structure and complete selenization. Under a three-electrode system with 2.0 M KOH as the electrolyte, CoSe₂/NC-1 possesses a high capacity of 554.4F/g at 1 A/g and excellent cycling stability (92% capacity retention after 21,000 cycles). In addition, a flexible solid-state supercapacitor was assembled with CoSe₂/NC-1 as the positive electrode and AC as the negative electrode. The power density was 800 W/Kg at 1 A/g, and the cycling stability was tested at 91.53% after 6000 cycles at 2 A/g. The flexible solid-state supercapacitors were tested for suppleness, and their voltage could still reach 1.6 V with stable specific capacity and light up LED bulbs when measured at 0°, 90° and 180°. Undoubtedly, the CoSe₂/NC-1 material prepared in this study exhibits promising electrochemical characteristics, making it a viable candidate for implementation in flexible solid-state supercapacitors.