Abstract <p>Recycling waste substances into economically valuable energy storage electrodes has been gaining great attention in recent years. In this work, we developed copper salt-free synthesis of porous copper oxide (CuO) nanoflakes and reduced graphene oxide from the graphite/Cu foil anode of spent Li-ion batteries. Specifically, the CuO nanoflakes were achieved through an electrochemical oxidation method with the recycled copper foil and investigated their structural and morphological features. The synthesized CuO showed monoclinic crystal structure, porosity and nanoflake morphology. The electrochemical performance of porous CuO nanoflakes was investigated in a three-electrode setup, exhibiting a high specific capacitance of 311.8 F g⁻¹ with a specific capacity of 152.8C g⁻¹ at discharge current density of 2&#xa0;mA&#xa0;cm⁻² and rate capability of 62.4% at high discharge current density of 20&#xa0;mA&#xa0;cm⁻². Additionally, reduced graphene oxide was prepared using the graphite waste, which showed excellent capacitive behavior with an excellent rate capability of 81.6%. Finally, the asymmetric supercapacitor was fabricated with CuO as a cathode and reduced graphene oxide as the negative electrode, demonstrated excellent cycling stability with 90% capacitance retention over 5000 cycles and a high energy and power densities of 35.5 Wh kg⁻¹ and 5085 W kg⁻¹, respectively. The asymmetric supercapacitor (ASC) device was successfully used to power a light-emitting diode (LED), showcasing its practical potential with effective recycling approaches into high-performance supercapacitor materials, promoting both sustainability and advanced energy storage solutions.</p> Graphical Abstract <p></p>