Binary strontium–copper oxide nanostructures doped with potassium as electrode material for supercapacitor application

Recently, binary metal-oxide--based electrode materials with and without doping have attracted growing interest for application to supercapacitors (SCs). Herein, we demonstrate the synthesis of a K-doped (ca. 9%) binary Sr–Cu metal oxide (K-SrCu₂O₂; KSCO) by a simple solid-state reaction with good crystallinity. The KSCO-modified carbon-cloth (CC) electrode showed a wide electrochemical potential window (− 0.2 to 0.8 V) and delivered a specific capacitance (C_s) of 438 F g⁻¹ at 1 A g⁻¹, compared to the low value (14.5 F g⁻¹ at 1 A g⁻¹) for the undoped SrCu₂O₂ (SCO)-modified electrode. This substantially improved C_s for SCO upon K-doping can be attributed to the increased conductivity, which enhanced the rate of ion intercalation/deintercalation into the tunnels of KSCO. Furthermore, the KSCO-modified electrode exhibited high-electrochemical stability with a capacitance loss of only 10% after 5000 charge–discharge cycles.