Interlayer-Expanded Metal Oxide/Sulfide Composites for Ultrastable Flexible Hybrid Supercapacitors

Rationally designed nanoarchitectures with optimized electrochemical behavior provide a unique strategy to improve the redox kinetics of battery electrodes, enabling the simultaneous delivery of high energy and power densities. Here, we report a molybdate-ion intercalated oxide/sulfide composite material prepared hydrothermally enabling precise regulation of the chemical environment and electronic structure of the metal active site, thereby enhancing the pseudocapacitive current contribution. The resulting ZnMoO₄/CoMoS₄ nanostructures are uniformly anchored onto the Cu foil, forming abundant, synergistically coupled interfaces and junctions that endow the composite with high porosity, enlarged interlayer spacing, and superior electrical conductivity. These structural advantages yield an exceptional specific capacitance of 2238.75 F g^-1 (310.93 mAh g^-1) at 1.2 A g^-1, alongside improved ion transport and reduced charge transfer resistance. When integrated into a flexible asymmetric supercapacitor (ZnMoO₄/CoMoS₄||AC), the device delivers a remarkable energy density of 58.3 Wh kg^-1 at a power density of 637.7 W kg^-1, retaining 91.7% of its capacitance after 2000 cycles. This work demonstrates a versatile and scalable strategy for engineering high performance metal oxide/sulfide hybrid electrodes, offering valuable insights for next generation flexible energy storage systems.