NiMnO3-reduced graphene oxide (rGO) nanocomposites as flexible yarn supercapacitor electrode material are synthesized by hydrothermal method. The prepared active materials are decorated on a yarn, including twisted cotton thread and very thin copper wire. These yarn electrodes are supercapacitor electrodes and characterized by structural, morphological, and chemical bonding. The results demonstrate that the presence of the graphene oxide compound has a synergistic effect on the electrochemical performance of these nanocomposites. The maximum specific capacitance of 404.4 mF cm-2 is obtained for these nanocomposites at a scan rate of 5 mV s-1 in a 1 M KOH solution electrolyte. Also, the results show that the capacitive-controlled process has a dominant contribution to their storage mechanism. As a flexible all-solid-state supercapacitor device, a symmetric yarn supercapacitor cell is fabricated by these coated yarns and KOH/PVA gel as the electrode and electrolyte, respectively. This yarn supercapacitor reveals a maximum specific capacitance of 83.4 mF cm-2. It provides a specific energy density of 17.5 µWh cm-2 at a specific power density of 383.5 µW cm-2 in a potential range of 1.7 V. Furthermore, the capacitive performance of the yarn supercapacitor device remains unaffected even when subjected to bending, demonstrating its exceptional flexibility.

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