A Graphene/SiO2/MnO/Graphene-SiC composite electrode printed on tinned steel for the fabrication of supercapacitors with high energy density

Abstract Metallic supercapacitors (SCs) were fabricated with graphene electrodes printed on tinned steel (MT) foils. Later, SiO 2 /MnO/Graphene-SiC nanocomposite (SiC-Mn) was deposited on the supercapacitor (SC) electrodes to enhance their capacitance. Firstly, the metal SCs were electrochemically tested in a flat state. The results showed that the SCs made with SiC-Mn powder had capacitance/energy density values of 1048.8 F g −1 /209.6 Wh kg −1 , while those made without SiC-Mn powder had lower values of 141.8 F g −1 /28.4 Wh kg −1 . Consequently, incorporating SiC-Mn powder into the SCs enhanced the capacitance 6.4 times. When the metallic SC is bent at 30°, the capacitance/energy density values were enhanced up to 1562.8 F g −1 and 312.5 Wh kg −1 , respectively. This last effect occurred because extra pores were formed on the SC electrodes at the bent state, which favored the charge storage. Interestingly, the SC operating voltage can be controlled with folding/unfolding, since the operating voltage was increased from ⁓0.55 V to 0.71 after passing the device from a flat to a bent state, but it returned to 0.55 V after unfolding the device. Additionally, the device made with SiC-Mn powder was tested at a low-temperature of 2 °C and still showed high capacitance/energy density values of 433.5 F g −1 and 86.7 Wh kg −1 , respectively. Raman, UV–Vis, and XPS analyses were carried out on the metallic electrodes and detected oxygen-vacancy defects as well as Si 3 ⁺/Si 4 ⁺ and Mn 2+ /Mn 3 ⁺/Mn 4 ⁺ species, which worked as the redox centers for the charge storage. In general, it was demonstrated that low-cost SCs could be fabricated using MT/SiC-Mn composite.