Flexible solid-state asymmetric supercapacitor based on reduced graphene oxide (rGO)/ruthenium oxide (RuO₂) composite electrode

Energy storage in flexible supercapacitor devices extensively depends on electrode design with good electrochemical as well as mechanical properties. Here, a cost-effective and scalable method is proposed for the synthesis of a reduced graphene oxide/ruthenium oxide (rGO/RuO₂) composite thin film for flexible supercapacitor. The successive ionic layer adsorption and reaction (SILAR) method used to synthesize rGO/RuO₂ composite electrode allowed the synthesis of amorphous RuO₂ with optimized rGO composition. The morphological structure of rGO/RuO₂ composite examined using a scanning electron microscope showed compact spherical microparticles coated on rGO sheets. The electrochemical measurements of rGO/RuO₂ composite electrode revealed that the composite material achieved a specific capacitance of 1371 F g⁻¹ at a scan rate of 5 mV s⁻¹. Due to the combined impact of rGO and RuO₂, a flexible solid-state asymmetric supercapacitor (FSS-ASC) of configuration rGO/RuO₂/PVA-H₂SO₄/WO₃ exhibited C_s of 114 F g⁻¹ at 5 mV s⁻¹ with 88% of capacitance retention after 5000 galvanostatic charge-discharge (GCD) cycles. The FSS-ASC provided a remarkable specific energy of 23 Wh kg⁻¹ and a specific power of 613 W kg⁻¹. The electrochemical features of rGO/RuO₂ composite show a promising way to fabricate flexible supercapacitors.