Dual-Window Electrochemical Application of a MoS₂@NiFe₂O₄ Spinel Hybrid Heterostructure: High-Performance Asymmetric and Symmetric Supercapacitors

In this work, MoS₂@NiFe₂O₄ nanocomposites were engineered as electrode materials for both asymmetric (ASSC) and symmetric supercapacitors (SSC). The hybrid electrode combines the layered structure of MoS₂ and the redox-active spinel framework of NiFe₂O₄, offering better electrochemical performance. In the asymmetric configuration, the device demonstrated dual-potential-window functionality over –1.2 to 1.2 V, yielding strong redox activity and pseudocapacitive behavior with a specific capacitance of 102.36 F g⁻¹ at 10 mV s⁻¹. In addition, the ASSC attained an energy density of 12.08 Wh kg⁻¹ at a power density of 750 W kg⁻¹, exhibiting a Coulombic efficiency of 97.1% and a capacitance retention of 97.22% over 10,000 cycles. A high specific capacitance of 517.57 F g⁻¹ was achieved at a scan rate of 10 mV s⁻¹, and 483.42 F g⁻¹ was recorded using galvanostatic charge–discharge at 1 mA. The SSC achieved an energy density of 67.14 Wh kg⁻¹ at 750 W kg⁻¹ and maintained 99.25% of its capacitance after 10,000 cycles, exhibiting remarkably nearly 100% Coulombic efficiency. Mechanical flexibility tests confirmed the device's outstanding structural integrity under bending and twisting, indicating its applicability for flexible energy storage applications.