Microwave-assisted engineering of spinel ferrite–graphene nanohybrids for high-energy asymmetric supercapacitors

Supercapacitors are widely known for their high power density, fast charge-discharge rates, and excellent cycling stability. However, enhancing the energy density of supercapacitors while maintaining their high power remains a key challenge for this electrochemical energy storage device. In this work, spinel ferrite–graphene nanohybrids are synthesized via a microwave-assisted co-precipitation method. This approach enables the rapid, uniform decoration of ferrite nanoparticles on graphene nanosheets. Structural characterization confirms the in-situ formation of crystalline spinel phases embedded within the graphene matrix under controlled thermal conditions. Electrochemical measurements reveal that the charge storage process is mainly diffusion-controlled due to the redox activity of the ferrite phase. The optimized electrode delivers a specific capacitance of 1467 F g –1 at a current density of 1 A g –1 , along with reasonable rate capability. Moreover, an all-solid-state asymmetric supercapacitor (ASC) device is assembled using the optimized nanohybrid. The ASC device achieves a notable energy density of 86.53 Wh kg –1 and a power density of 4882.35 W kg –1 . Furthermore, the device maintains stable cycling performance over 10,000 cycles. These results provide an evolution of spinel ferrite–graphene nanohybrids and the critical role of interfacial design in enhancing the electrochemical performance of such nanohybrids.