Dual‐Window Electrochemical Application of a MoS 2 @NiFe 2 O 4 Spinel Hybrid Heterostructure: High‐Performance Asymmetric and Symmetric Supercapacitors

ABSTRACT In this work, MoS 2 @NiFe 2 O 4 nanocomposites were engineered as electrode materials for both asymmetric (ASSC) and symmetric supercapacitors (SSC). The hybrid electrode combines the layered structure of MoS 2 and the redox‐active spinel framework of NiFe 2 O 4 , 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.